1
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Attar AG, Paturej J, Banigan EJ, Erbaş A. Chromatin phase separation and nuclear shape fluctuations are correlated in a polymer model of the nucleus. Nucleus 2024; 15:2351957. [PMID: 38753956 DOI: 10.1080/19491034.2024.2351957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Accepted: 04/28/2024] [Indexed: 05/18/2024] Open
Abstract
Abnormal cell nuclear shapes are hallmarks of diseases, including progeria, muscular dystrophy, and many cancers. Experiments have shown that disruption of heterochromatin and increases in euchromatin lead to nuclear deformations, such as blebs and ruptures. However, the physical mechanisms through which chromatin governs nuclear shape are poorly understood. To investigate how heterochromatin and euchromatin might govern nuclear morphology, we studied chromatin microphase separation in a composite coarse-grained polymer and elastic shell simulation model. By varying chromatin density, heterochromatin composition, and heterochromatin-lamina interactions, we show how the chromatin phase organization may perturb nuclear shape. Increasing chromatin density stabilizes the lamina against large fluctuations. However, increasing heterochromatin levels or heterochromatin-lamina interactions enhances nuclear shape fluctuations by a "wetting"-like interaction. In contrast, fluctuations are insensitive to heterochromatin's internal structure. Our simulations suggest that peripheral heterochromatin accumulation could perturb nuclear morphology, while nuclear shape stabilization likely occurs through mechanisms other than chromatin microphase organization.
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Affiliation(s)
- Ali Goktug Attar
- UNAM-National Nanotechnology Research Center and Institute of Materials Science & Nanotechnology, Bilkent University, Ankara, Turkey
| | | | - Edward J Banigan
- Institute for Medical Engineering and Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Aykut Erbaş
- UNAM-National Nanotechnology Research Center and Institute of Materials Science & Nanotechnology, Bilkent University, Ankara, Turkey
- Institute of Physics, University of Silesia, Chorzów, Poland
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2
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Niekamp S, Marr SK, Oei TA, Subramanian R, Kingston RE. Modularity of PRC1 composition and chromatin interaction define condensate properties. Mol Cell 2024; 84:1651-1666.e12. [PMID: 38521066 DOI: 10.1016/j.molcel.2024.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 01/04/2024] [Accepted: 02/29/2024] [Indexed: 03/25/2024]
Abstract
Polycomb repressive complexes (PRCs) play a key role in gene repression and are indispensable for proper development. Canonical PRC1 forms condensates in vitro and in cells that are proposed to contribute to the maintenance of repression. However, how chromatin and the various subunits of PRC1 contribute to condensation is largely unexplored. Using a reconstitution approach and single-molecule imaging, we demonstrate that nucleosomal arrays and PRC1 act synergistically, reducing the critical concentration required for condensation by more than 20-fold. We find that the exact combination of PHC and CBX subunits determines condensate initiation, morphology, stability, and dynamics. Particularly, PHC2's polymerization activity influences condensate dynamics by promoting the formation of distinct domains that adhere to each other but do not coalesce. Live-cell imaging confirms CBX's role in condensate initiation and highlights PHC's importance for condensate stability. We propose that PRC1 composition can modulate condensate properties, providing crucial regulatory flexibility across developmental stages.
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Affiliation(s)
- Stefan Niekamp
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Sharon K Marr
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Theresa A Oei
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Department of Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Radhika Subramanian
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
| | - Robert E Kingston
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
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3
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Deshpande P, Prentice E, Vidal Ceballos A, Casaccia P, Elbaum-Garfinkle S. Epigenetic marks uniquely tune the material properties of HP1α condensates. Biophys J 2024:S0006-3495(24)00282-0. [PMID: 38664966 DOI: 10.1016/j.bpj.2024.04.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/20/2024] [Accepted: 04/22/2024] [Indexed: 05/07/2024] Open
Abstract
Biomolecular condensates have emerged as a powerful new paradigm in cell biology with broad implications to human health and disease, particularly in the nucleus where phase separation is thought to underly elements of chromatin organization and regulation. Specifically, it has been recently reported that phase separation of heterochromatin protein 1alpha (HP1α) with DNA contributes to the formation of condensed chromatin states. HP1α localization to heterochromatic regions is mediated by its binding to specific repressive marks on the tail of histone H3, such as trimethylated lysine 9 on histone H3 (H3K9me3). However, whether epigenetic marks play an active role in modulating the material properties of HP1α and dictating emergent functions of its condensates remains to be understood. Here, we leverage a reductionist system, composed of modified and unmodified histone H3 peptides, HP1α, and DNA, to examine the contribution of specific epigenetic marks to phase behavior of HP1α. We show that the presence of histone peptides bearing the repressive H3K9me3 is compatible with HP1α condensates, whereas peptides containing unmodified residues or bearing the transcriptional activation mark H3K4me3 are incompatible with HP1α phase separation. Using fluorescence microscopy and rheological approaches, we further demonstrate that H3K9me3 histone peptides modulate the dynamics and viscoelastic network properties of HP1α condensates in a concentration-dependent manner. Additionally, in cells exposed to uniaxial strain, we find there to be a decreased ratio of nuclear H3K9me3 to HP1α. These data suggest that HP1α-DNA condensates are viscoelastic materials, whose properties may provide an explanation for the dynamic behavior of heterochromatin in cells and in response to mechanostimulation.
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Affiliation(s)
- Priyasha Deshpande
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, New York, New York; Structural Biology Initiative, Advanced Science Research Center, CUNY, New York, New York
| | - Emily Prentice
- Ph.D. Program in Biology, Graduate Center of the City University of New York, New York, New York; Neuroscience Initiative, Advanced Science Research Center, CUNY, New York, New York
| | - Alfredo Vidal Ceballos
- Structural Biology Initiative, Advanced Science Research Center, CUNY, New York, New York
| | - Patrizia Casaccia
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, New York, New York; Ph.D. Program in Biology, Graduate Center of the City University of New York, New York, New York; Neuroscience Initiative, Advanced Science Research Center, CUNY, New York, New York.
| | - Shana Elbaum-Garfinkle
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, New York, New York; Ph.D. Program in Biology, Graduate Center of the City University of New York, New York, New York; Structural Biology Initiative, Advanced Science Research Center, CUNY, New York, New York; Ph.D. Program in Chemistry, Graduate Center of the City University of New York, New York.
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4
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Bryant L, Sangree A, Clark K, Bhoj E. Histone 3.3-related chromatinopathy: missense variants throughout H3-3A and H3-3B cause a range of functional consequences across species. Hum Genet 2024; 143:497-510. [PMID: 36867246 DOI: 10.1007/s00439-023-02536-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 02/20/2023] [Indexed: 03/04/2023]
Abstract
There has been considerable recent interest in the role that germline variants in histone genes play in Mendelian syndromes. Specifically, missense variants in H3-3A and H3-3B, which both encode Histone 3.3, were discovered to cause a novel neurodevelopmental disorder, Bryant-Li-Bhoj syndrome. Most of the causative variants are private and scattered throughout the protein, but all seem to have either a gain-of-function or dominant negative effect on protein function. This is highly unusual and not well understood. However, there is extensive literature about the effects of Histone 3.3 mutations in model organisms. Here, we collate the previous data to provide insight into the elusive pathogenesis of missense variants in Histone 3.3.
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Affiliation(s)
- Laura Bryant
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Annabel Sangree
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Kelly Clark
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Elizabeth Bhoj
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA.
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5
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Liu N, Qiang W, Jordan P, Marko J, Qiao H. Cell-cycle and Age-Related Modulations in Mouse Chromosome Stiffness. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.06.583771. [PMID: 38559262 PMCID: PMC10979861 DOI: 10.1101/2024.03.06.583771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The intricate structure of chromosomes is complex, and many aspects of chromosome configuration/organization remain to be fully understood. Measuring chromosome stiffness can provide valuable insights into their structure. However, the nature of chromosome stiffness, whether static or dynamic, remains elusive. In this study, we analyzed chromosome stiffness in MI and MII oocytes. We revealed that MI oocytes had a ten-fold increase in stiffness compared to mitotic chromosomes, whereas chromosome stiffness in MII oocytes was relatively low chromosome. We then investigated the contribution of meiosis-specific cohesin complexes to chromosome stiffness in MI and MII oocytes. Surprisingly, the Young's modulus of chromosomes from the three meiosis-specific cohesin mutants did not exhibit significant differences compared to the wild type, indicating that these proteins may not play a substantial role in determining chromosome stiffness. Additionally, our findings revealed an age-related increase in chromosome stiffness in MI oocytes. Age correlates with elevated DNA damage levels, so we investigated the impact of etoposide-induced DNA damage on chromosome stiffness, discovering a reduction in stiffness in response to such damage in MI oocytes. Overall, our study underscores the dynamic nature of chromosome stiffness, subject to changes influenced by the cell cycle and age.
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Affiliation(s)
- Ning Liu
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Wenan Qiang
- Center for Developmental Therapeutics, Northwestern University, Evanston, IL, USA
| | - Philip Jordan
- Biochemistry and Molecular Biology Departments, Johns Hopkins University, Baltimore, MD, USA
- School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - John Marko
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, USA
| | - Huanyu Qiao
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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6
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Deviri D, Safran SA. Mechanosensitivity of phase separation in an elastic gel. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2024; 47:16. [PMID: 38376695 PMCID: PMC10879317 DOI: 10.1140/epje/s10189-024-00405-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 01/02/2024] [Indexed: 02/21/2024]
Abstract
Liquid-liquid phase separation (LLPS) in binary or multi-component solutions is a well-studied subject in soft matter with extensive applications in biological systems. In recent years, several experimental studies focused on LLPS of solutes in hydrated gels, where the formation of coexisting domains induces elastic deformations within the gel. While the experimental studies report unique physical characteristics of these systems, such as sensitivity to mechanical forces and stabilization of multiple, periodic phase-separated domains, the theoretical understanding of such systems and the role of long-range interactions have not emphasized the nonlinear nature of the equilibrium binodal for strong segregation of the solute. In this paper, we formulate a generic, mean-field theory of a hydrated gel in the presence of an additional solute which changes the elastic properties of the gel. We derive equations for the equilibrium binodal of the phase separation of the solvent and solute and show that the deformations induced by the solute can result in effective long-range interactions between phase-separating solutes that can either enhance or, in the case of externally applied pressure, suppress phase separation of the solute relative to the case where there is no gel. This causes the coexisting concentrations at the binodal to depend on the system-wide average concentration, in contrast to the situation for phase separation in the absence of the gel.
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Affiliation(s)
- Dan Deviri
- Department of Chemical and Biological Physics, Weizmann Institute of Science, 76100, Rehovot, Israel.
- Carbon Blue Ltd., 3303201, Haifa, Israel.
| | - Samuel A Safran
- Department of Chemical and Biological Physics, Weizmann Institute of Science, 76100, Rehovot, Israel
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7
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Deshpande P, Prentice E, Ceballos AV, Casaccia P, Elbaum-Garfinkle S. Modified histone peptides uniquely tune the material properties of HP1α condensates. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.07.579285. [PMID: 38370661 PMCID: PMC10871333 DOI: 10.1101/2024.02.07.579285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Biomolecular condensates have emerged as a powerful new paradigm in cell biology with broad implications to human health and disease, particularly in the nucleus where phase separation is thought to underly elements of chromatin organization and regulation. Specifically, it has been recently reported that phase separation of heterochromatin protein 1alpha (HP1α) with DNA contributes to the formation of condensed chromatin states. HP1α localization to heterochromatic regions is mediated by its binding to specific repressive marks on the tail of histone H3, such as trimethylated lysine 9 on histone H3 (H3K9me3). However, whether epigenetic marks play an active role in modulating the material properties of HP1α and dictating emergent functions of its condensates, remains only partially understood. Here, we leverage a reductionist system, comprised of modified and unmodified histone H3 peptides, HP1α and DNA to examine the contribution of specific epigenetic marks to phase behavior of HP1α. We show that the presence of histone peptides bearing the repressive H3K9me3 is compatible with HP1α condensates, while peptides containing unmodified residues or bearing the transcriptional activation mark H3K4me3 are incompatible with HP1α phase separation. In addition, inspired by the decreased ratio of nuclear H3K9me3 to HP1α detected in cells exposed to uniaxial strain, using fluorescence microscopy and rheological approaches we demonstrate that H3K9me3 histone peptides modulate the dynamics and network properties of HP1α condensates in a concentration dependent manner. These data suggest that HP1α-DNA condensates are viscoelastic materials, whose properties may provide an explanation for the dynamic behavior of heterochromatin in cells in response to mechanostimulation.
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Affiliation(s)
- Priyasha Deshpande
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, NY
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Structural Biology Initiative, Advanced Science Research Center, CUNY, New York, NY
| | - Emily Prentice
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Neuroscience Initiative, Advanced Science Research Center, CUNY, New York, NY
| | | | - Patrizia Casaccia
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, NY
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Neuroscience Initiative, Advanced Science Research Center, CUNY, New York, NY
| | - Shana Elbaum-Garfinkle
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, NY
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Structural Biology Initiative, Advanced Science Research Center, CUNY, New York, NY
- Ph.D. Program in Chemistry, Graduate Center of the City University of New York, NY
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8
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Bunner S, Prince K, Srikrishna K, Pujadas EM, McCarthy AA, Kuklinski A, Jackson O, Pellegrino P, Jagtap S, Eweka I, Lawlor C, Eastin E, Yas G, Aiello J, LaPointe N, von Blucher IS, Hardy J, Chen J, Backman V, Janssen A, Packard M, Dorfman K, Almassalha L, Bahiru MS, Stephens AD. DNA density is a better indicator of a nuclear bleb than lamin B loss. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.06.579152. [PMID: 38370828 PMCID: PMC10871186 DOI: 10.1101/2024.02.06.579152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Nuclear blebs are herniations of the nucleus that occur in diseased nuclei that cause nuclear rupture leading to cellular dysfunction. Chromatin and lamins are two of the major structural components of the nucleus that maintain its shape and function, but their relative roles in nuclear blebbing remain elusive. Lamin B is reported to be lost in blebs by qualitative data while quantitative studies reveal a spectrum of lamin B levels in nuclear blebs dependent on perturbation and cell type. Chromatin has been reported to be decreased or de-compacted in nuclear blebs, but again the data are not conclusive. To determine the composition of nuclear blebs, we compared the immunofluorescence intensity of lamin B and DNA in the main nucleus body and nuclear bleb across cell types and perturbations. Lamin B nuclear bleb levels varied drastically across MEF wild type and chromatin or lamins perturbations, HCT116 lamin B1-GFP imaging, and human disease model cells of progeria and prostate cancer. However, DNA concentration was consistently decreased to about half that of the main nucleus body across all measured conditions. Using Partial Wave Spectroscopic (PWS) microscopy to measure chromatin density in the nuclear bleb vs body we find similar results that DNA is consistently less dense in nuclear blebs. Thus, our data spanning many different cell types and perturbations supports that decreased DNA is a better marker of a nuclear bleb than lamin B levels that vary widely.
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Affiliation(s)
- Samantha Bunner
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Kelsey Prince
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Karan Srikrishna
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Emily Marie Pujadas
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- IBIS Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA
| | | | - Anna Kuklinski
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Olivia Jackson
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Pedro Pellegrino
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Shrushti Jagtap
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Imuetiyan Eweka
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Colman Lawlor
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Emma Eastin
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Griffin Yas
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Julianna Aiello
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Nathan LaPointe
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | | | - Jillian Hardy
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Jason Chen
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Anne Janssen
- School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Mary Packard
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Katherine Dorfman
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
| | - Luay Almassalha
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Michael Seifu Bahiru
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
- Program in Neuroscience and Behavior, University of Massachusetts, Amherst, MA 01003, USA
| | - A. D. Stephens
- Biology department, University of Massachusetts Amherst, Amherst, MA. 01003, USA
- Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
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9
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Pho M, Berrada Y, Gunda A, Lavallee A, Chiu K, Padam A, Currey ML, Stephens AD. Actin contraction controls nuclear blebbing and rupture independent of actin confinement. Mol Biol Cell 2024; 35:ar19. [PMID: 38088876 PMCID: PMC10881147 DOI: 10.1091/mbc.e23-07-0292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 11/03/2023] [Accepted: 11/27/2023] [Indexed: 01/14/2024] Open
Abstract
The nucleus is a mechanically stable compartment of the cell that contains the genome and performs many essential functions. Nuclear mechanical components chromatin and lamins maintain nuclear shape, compartmentalization, and function by resisting antagonistic actin contraction and confinement. Studies have yet to compare chromatin and lamins perturbations side-by-side as well as modulated actin contraction while holding confinement constant. To accomplish this, we used nuclear localization signal green fluorescent protein to measure nuclear shape and rupture in live cells with chromatin and lamin perturbations. We then modulated actin contraction while maintaining actin confinement measured by nuclear height. Wild type, chromatin decompaction, and lamin B1 null present bleb-based nuclear deformations and ruptures dependent on actin contraction and independent of actin confinement. Actin contraction inhibition by Y27632 decreased nuclear blebbing and ruptures while activation by CN03 increased rupture frequency. Lamin A/C null results in overall abnormal shape also reliant on actin contraction, but similar blebs and ruptures as wild type. Increased DNA damage is caused by nuclear blebbing or abnormal shape which can be relieved by inhibition of actin contraction which rescues nuclear shape and decreases DNA damage levels in all perturbations. Thus, actin contraction drives nuclear blebbing, bleb-based ruptures, and abnormal shape independent of changes in actin confinement.
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Affiliation(s)
- Mai Pho
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
| | - Yasmin Berrada
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
| | - Aachal Gunda
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
| | - Anya Lavallee
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
| | - Katherine Chiu
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
| | - Arimita Padam
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
| | - Marilena L. Currey
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
| | - Andrew D. Stephens
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003
- Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
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10
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Seelbinder B, Wagner S, Jain M, Erben E, Klykov S, Stoev ID, Krishnaswamy VR, Kreysing M. Probe-free optical chromatin deformation and measurement of differential mechanical properties in the nucleus. eLife 2024; 13:e76421. [PMID: 38214505 PMCID: PMC10786458 DOI: 10.7554/elife.76421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 11/29/2023] [Indexed: 01/13/2024] Open
Abstract
The nucleus is highly organized to facilitate coordinated gene transcription. Measuring the rheological properties of the nucleus and its sub-compartments will be crucial to understand the principles underlying nuclear organization. Here, we show that strongly localized temperature gradients (approaching 1°C/µm) can lead to substantial intra-nuclear chromatin displacements (>1 µm), while nuclear area and lamina shape remain unaffected. Using particle image velocimetry (PIV), intra-nuclear displacement fields can be calculated and converted into spatio-temporally resolved maps of various strain components. Using this approach, we show that chromatin displacements are highly reversible, indicating that elastic contributions are dominant in maintaining nuclear organization on the time scale of seconds. In genetically inverted nuclei, centrally compacted heterochromatin displays high resistance to deformation, giving a rigid, solid-like appearance. Correlating spatially resolved strain maps with fluorescent reporters in conventional interphase nuclei reveals that various nuclear compartments possess distinct mechanical identities. Surprisingly, both densely and loosely packed chromatin showed high resistance to deformation, compared to medium dense chromatin. Equally, nucleoli display particularly high resistance and strong local anchoring to heterochromatin. Our results establish how localized temperature gradients can be used to drive nuclear compartments out of mechanical equilibrium to obtain spatial maps of their material responses.
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Affiliation(s)
- Benjamin Seelbinder
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Centre for Systems BiologyDresdenGermany
| | - Susan Wagner
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Institute of Biological and Chemical Systems-Biological Information Processing, Karlsruhe Institute of TechnologyEggenstein-LeopoldshafenGermany
| | - Manavi Jain
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Centre for Systems BiologyDresdenGermany
| | - Elena Erben
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Centre for Systems BiologyDresdenGermany
| | - Sergei Klykov
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Centre for Systems BiologyDresdenGermany
| | - Iliya Dimitrov Stoev
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Centre for Systems BiologyDresdenGermany
| | | | - Moritz Kreysing
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Centre for Systems BiologyDresdenGermany
- Institute of Biological and Chemical Systems-Biological Information Processing, Karlsruhe Institute of TechnologyEggenstein-LeopoldshafenGermany
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11
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Tam PLF, Cheung MF, Chan LY, Leung D. Cell-type differential targeting of SETDB1 prevents aberrant CTCF binding, chromatin looping, and cis-regulatory interactions. Nat Commun 2024; 15:15. [PMID: 38167730 PMCID: PMC10762014 DOI: 10.1038/s41467-023-44578-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 12/19/2023] [Indexed: 01/05/2024] Open
Abstract
SETDB1 is an essential histone methyltransferase that deposits histone H3 lysine 9 trimethylation (H3K9me3) to transcriptionally repress genes and repetitive elements. The function of differential H3K9me3 enrichment between cell-types remains unclear. Here, we demonstrate mutual exclusivity of H3K9me3 and CTCF across mouse tissues from different developmental timepoints. We analyze SETDB1 depleted cells and discover that H3K9me3 prevents aberrant CTCF binding independently of DNA methylation and H3K9me2. Such sites are enriched with SINE B2 retrotransposons. Moreover, analysis of higher-order genome architecture reveals that large chromatin structures including topologically associated domains and subnuclear compartments, remain intact in SETDB1 depleted cells. However, chromatin loops and local 3D interactions are disrupted, leading to transcriptional changes by modifying pre-existing chromatin landscapes. Specific genes with altered expression show differential interactions with dysregulated cis-regulatory elements. Collectively, we find that cell-type specific targets of SETDB1 maintain cellular identities by modulating CTCF binding, which shape nuclear architecture and transcriptomic networks.
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Affiliation(s)
- Phoebe Lut Fei Tam
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, SAR, China
| | - Ming Fung Cheung
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, SAR, China
- Center for Epigenomics Research, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, SAR, China
| | - Lu Yan Chan
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, SAR, China
- Center for Epigenomics Research, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, SAR, China
| | - Danny Leung
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, SAR, China.
- Center for Epigenomics Research, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, SAR, China.
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12
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Zhou ZK, Narlikar GJ. Understanding how genetically encoded tags affect phase separation by Heterochromatin Protein HP1α. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.04.569983. [PMID: 38106110 PMCID: PMC10723358 DOI: 10.1101/2023.12.04.569983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Liquid-liquid phase separation (LLPS) is driven by weak multi-valent interactions. Such interactions can result in the formation of puncta in cells and droplets in vitro . The heterochromatin protein HP1α forms droplets with chromatin in vitro and is found in puncta in cells. A common approach to visualize the dynamics of HP1α in cells is to genetically encode fluorescent tags on the protein. HP1α modified with tags such as GFP has been shown to localize to dynamic puncta in vivo . However, whether tagged HP1α retains its intrinsic phase separation properties has not been systematically studied. Here, using different C-terminal tags (AID-sfGFP, mEGFP, and UnaG), we assessed how tag size and linker length affected the phase separation ability of HP1α with DNA in vitro . We found that the AID-sfGFP tag (52 kDa) promoted HP1α phase-separation, possibly driven by the highly disordered AID degron. The mEGFP tag (27 kDa) inhibited phase-separation by HP1α, whereas an UnaG tag (13 kDa) with a 16 amino acid linker showed minimal perturbation. The UnaG tag can thus be used in cellular studies of HP1α to better correlate in vitro and in vivo studies. To test if cellular crowding overcomes the negative effects of large tags in vivo , we used polyethylene glycol (PEG) to mimic crowding in vitro . We found that addition of 10% PEG8000 or PEG4000 enables phase separation by GFP-tagged HP1α at comparable concentrations as untagged HP1α. However, these crowding agents also substantially dampened the differences in phase-separation between wild-type and mutant HP1α proteins. PEG further drove phase-separation of Maltose Binding Protein (MBP), a tag often used to solubilize other proteins. These results suggest that phase-separation of biological macromolecules with PEG should be interpreted with caution as PEG-based crowding agents may change the types of interactions made within the phases.
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13
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Elathram N, Ackermann BE, Clark ET, Dunn SR, Debelouchina GT. Phosphorylated HP1α-Nucleosome Interactions in Phase Separated Environments. J Am Chem Soc 2023; 145:23994-24004. [PMID: 37870432 PMCID: PMC10636758 DOI: 10.1021/jacs.3c06481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 10/03/2023] [Accepted: 10/05/2023] [Indexed: 10/24/2023]
Abstract
In the nucleus, transcriptionally silent genes are sequestered into heterochromatin compartments comprising nucleosomes decorated with histone H3 Lys9 trimethylation and a protein called HP1α. This protein can form liquid-liquid droplets in vitro and potentially organize heterochromatin through a phase separation mechanism that is promoted by phosphorylation. Elucidating the molecular interactions that drive HP1α phase separation and its consequences on nucleosome structure and dynamics has been challenging due to the viscous and heterogeneous nature of such assemblies. Here, we tackle this problem by a combination of solution and solid-state NMR spectroscopy, which allows us to dissect the interactions of phosphorylated HP1α with nucleosomes in the context of phase separation. Our experiments indicate that phosphorylated human HP1α does not cause any major rearrangements to the nucleosome core, in contrast to the yeast homologue Swi6. Instead, HP1α interacts specifically with the methylated H3 tails and slows the dynamics of the H4 tails. Our results shed light on how phosphorylated HP1α proteins may regulate the heterochromatin landscape, while our approach provides an atomic resolution view of a heterogeneous and dynamic biological system regulated by a complex network of interactions and post-translational modifications.
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Affiliation(s)
- Nesreen Elathram
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Bryce E. Ackermann
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Evan T. Clark
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Shelby R. Dunn
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Galia T. Debelouchina
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
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14
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Bonucci M, Shu T, Holt LJ. How it feels in a cell. Trends Cell Biol 2023; 33:924-938. [PMID: 37286396 PMCID: PMC10592589 DOI: 10.1016/j.tcb.2023.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 05/01/2023] [Accepted: 05/02/2023] [Indexed: 06/09/2023]
Abstract
Life emerges from thousands of biochemical processes occurring within a shared intracellular environment. We have gained deep insights from in vitro reconstitution of isolated biochemical reactions. However, the reaction medium in test tubes is typically simple and diluted. The cell interior is far more complex: macromolecules occupy more than a third of the space, and energy-consuming processes agitate the cell interior. Here, we review how this crowded, active environment impacts the motion and assembly of macromolecules, with an emphasis on mesoscale particles (10-1000 nm diameter). We describe methods to probe and analyze the biophysical properties of cells and highlight how changes in these properties can impact physiology and signaling, and potentially contribute to aging, and diseases, including cancer and neurodegeneration.
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Affiliation(s)
- Martina Bonucci
- Institute for Systems Genetics, New York University Langone Medical Center, 435 E 30th Street, New York, NY 10016, USA
| | - Tong Shu
- Institute for Systems Genetics, New York University Langone Medical Center, 435 E 30th Street, New York, NY 10016, USA
| | - Liam J Holt
- Institute for Systems Genetics, New York University Langone Medical Center, 435 E 30th Street, New York, NY 10016, USA.
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15
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Niekamp S, Marr SK, Oei TA, Subramanian R, Kingston RE. Modularity of PRC1 Composition and Chromatin Interaction define Condensate Properties. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.26.564217. [PMID: 37961190 PMCID: PMC10634914 DOI: 10.1101/2023.10.26.564217] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Polycomb repressive complexes (PRC) play a key role in gene repression and are indispensable for proper development. Canonical PRC1 forms condensates in vitro and in cells and the ability of PRC1 to form condensates has been proposed to contribute to maintenance of repression. However, how chromatin and the various subunits of PRC1 contribute to condensation is largely unexplored. Using single-molecule imaging, we demonstrate that nucleosomal arrays and PRC1 act synergistically, reducing the critical concentration required for condensation by more than 20-fold. By reconstituting and imaging PRC1 with various subunit compositions, we find that the exact combination of PHC and CBX subunits determine the initiation, morphology, stability, and dynamics of condensates. In particular, the polymerization activity of PHC2 strongly influences condensate dynamics to promote formation of structures with distinct domains that adhere to each other but do not coalesce. Using live cell imaging, we confirmed that CBX properties are critical for condensate initiation and that PHC polymerization is important to maintain stable condensates. Together, we propose that PRC1 can fine-tune the degree and type of condensation by altering its composition which might offer important flexibility of regulatory function during different stages of development.
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16
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Pollin G, De Assuncao T, Doria Jorge S, Chi YI, Charlesworth M, Madden B, Iovanna J, Zimmermann M, Urrutia R, Lomberk G. Writers and readers of H3K9me2 form distinct protein networks during the cell cycle that include candidates for H3K9 mimicry. Biosci Rep 2023; 43:BSR20231093. [PMID: 37782747 PMCID: PMC10611923 DOI: 10.1042/bsr20231093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 09/15/2023] [Accepted: 10/02/2023] [Indexed: 10/04/2023] Open
Abstract
Histone H3 lysine 9 methylation (H3K9me), which is written by the Euchromatic Histone Lysine Methyltransferases EHMT1 and EHMT2 and read by the heterochromatin protein 1 (HP1) chromobox (CBX) protein family, is dysregulated in many types of cancers. Approaches to inhibit regulators of this pathway are currently being evaluated for therapeutic purposes. Thus, knowledge of the complexes supporting the function of these writers and readers during the process of cell proliferation is critical for our understanding of their role in carcinogenesis. Here, we immunopurified each of these proteins and used mass spectrometry to define their associated non-histone proteins, individually and at two different phases of the cell cycle, namely G1/S and G2/M. Our findings identify novel binding proteins for these writers and readers, as well as corroborate known interactors, to show the formation of distinct protein complex networks in a cell cycle phase-specific manner. Furthermore, there is an organizational switch between cell cycle phases for interactions among specific writer-reader pairs. Through a multi-tiered bioinformatics-based approach, we reveal that many interacting proteins exhibit histone mimicry, based on an H3K9-like linear motif. Gene ontology analyses, pathway enrichment, and network reconstruction inferred that these comprehensive EHMT and CBX-associated interacting protein networks participate in various functions, including transcription, DNA repair, splicing, and membrane disassembly. Combined, our data reveals novel complexes that provide insight into key functions of cell cycle-associated epigenomic processes that are highly relevant for better understanding these chromatin-modifying proteins during cell cycle and carcinogenesis.
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Affiliation(s)
- Gareth Pollin
- Linda T. and John A. Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Division of Research, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI Center, Medical College of Wisconsin, Milwaukee, WI, U.S.A
| | - Thiago M. De Assuncao
- Linda T. and John A. Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Division of Research, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI Center, Medical College of Wisconsin, Milwaukee, WI, U.S.A
| | - Salomao Doria Jorge
- Linda T. and John A. Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, WI, U.S.A
| | - Young-In Chi
- Linda T. and John A. Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Division of Research, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI Center, Medical College of Wisconsin, Milwaukee, WI, U.S.A
| | | | - Benjamin Madden
- Medical Genome Facility, Proteomics Core, Mayo Clinic, Rochester, MN, U.S.A
| | - Juan Iovanna
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM U1068, CNRS UMR 7258, Aix-Marseille Université and Institut Paoli-Calmettes, Parc Scientifique et Technologique de Luminy, Marseille, France
| | - Michael T. Zimmermann
- Linda T. and John A. Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Clinical and Translational Sciences Institute, Medical College of Wisconsin, Milwaukee, WI, U.S.A
| | - Raul Urrutia
- Linda T. and John A. Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Division of Research, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI Center, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, U.S.A
| | - Gwen Lomberk
- Linda T. and John A. Mellowes Center for Genomic Sciences and Precision Medicine, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Division of Research, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI Center, Medical College of Wisconsin, Milwaukee, WI, U.S.A
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, U.S.A
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17
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Liu JX, Haataja MP, Košmrlj A, Datta SS, Arnold CB, Priestley RD. Liquid-liquid phase separation within fibrillar networks. Nat Commun 2023; 14:6085. [PMID: 37770446 PMCID: PMC10539382 DOI: 10.1038/s41467-023-41528-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 09/06/2023] [Indexed: 09/30/2023] Open
Abstract
Complex fibrillar networks mediate liquid-liquid phase separation of biomolecular condensates within the cell. Mechanical interactions between these condensates and the surrounding networks are increasingly implicated in the physiology of the condensates and yet, the physical principles underlying phase separation within intracellular media remain poorly understood. Here, we elucidate the dynamics and mechanics of liquid-liquid phase separation within fibrillar networks by condensing oil droplets within biopolymer gels. We find that condensates constrained within the network pore space grow in abrupt temporal bursts. The subsequent restructuring of condensates and concomitant network deformation is contingent on the fracture of network fibrils, which is determined by a competition between condensate capillarity and network strength. As a synthetic analog to intracellular phase separation, these results further our understanding of the mechanical interactions between biomolecular condensates and fibrillar networks in the cell.
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Affiliation(s)
- Jason X Liu
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
- Princeton Materials Institute, Princeton University, Princeton, NJ, 08544, USA
| | - Mikko P Haataja
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
- Princeton Materials Institute, Princeton University, Princeton, NJ, 08544, USA
| | - Andrej Košmrlj
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
- Princeton Materials Institute, Princeton University, Princeton, NJ, 08544, USA
| | - Sujit S Datta
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Craig B Arnold
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
- Princeton Materials Institute, Princeton University, Princeton, NJ, 08544, USA
| | - Rodney D Priestley
- Princeton Materials Institute, Princeton University, Princeton, NJ, 08544, USA.
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA.
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18
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Chiu K, Berrada Y, Eskndir N, Song D, Fong C, Naughton S, Chen T, Moy S, Gyurmey S, James L, Ezeiruaku C, Capistran C, Lowey D, Diwanji V, Peterson S, Parakh H, Burgess AR, Probert C, Zhu A, Anderson B, Levi N, Gerlitz G, Packard MC, Dorfman KA, Bahiru MS, Stephens AD. CTCF is essential for proper mitotic spindle structure and anaphase segregation. Chromosoma 2023:10.1007/s00412-023-00810-w. [PMID: 37728741 DOI: 10.1007/s00412-023-00810-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 08/11/2023] [Accepted: 09/08/2023] [Indexed: 09/21/2023]
Abstract
Mitosis is an essential process in which the duplicated genome is segregated equally into two daughter cells. CTCF has been reported to be present in mitosis and has a role in localizing CENP-E, but its importance for mitotic fidelity remains to be determined. To evaluate the importance of CTCF in mitosis, we tracked mitotic behaviors in wild-type and two different CTCF CRISPR-based genetic knockdowns. We find that knockdown of CTCF results in prolonged mitoses and failed anaphase segregation via time-lapse imaging of SiR-DNA. CTCF knockdown did not alter cell cycling or the mitotic checkpoint, which was activated upon nocodazole treatment. Immunofluorescence imaging of the mitotic spindle in CTCF knockdowns revealed disorganization via tri/tetrapolar spindles and chromosomes behind the spindle pole. Imaging of interphase nuclei showed that nuclear size increased drastically, consistent with failure to divide the duplicated genome in anaphase. Long-term inhibition of CNEP-E via GSK923295 recapitulates CTCF knockdown abnormal mitotic spindles with polar chromosomes and increased nuclear sizes. Population measurements of nuclear shape in CTCF knockdowns do not display decreased circularity or increased nuclear blebbing relative to wild-type. However, failed mitoses do display abnormal nuclear morphologies relative to successful mitoses, suggesting that population images do not capture individual behaviors. Thus, CTCF is important for both proper metaphase organization and anaphase segregation which impacts the size and shape of the interphase nucleus likely through its known role in recruiting CENP-E.
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Affiliation(s)
- Katherine Chiu
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Yasmin Berrada
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Nebiyat Eskndir
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Dasol Song
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Claire Fong
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Sarah Naughton
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Tina Chen
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Savanna Moy
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Sarah Gyurmey
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Liam James
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Chimere Ezeiruaku
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Caroline Capistran
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Daniel Lowey
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Vedang Diwanji
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Samantha Peterson
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Harshini Parakh
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Ayanna R Burgess
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Cassandra Probert
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Annie Zhu
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Bryn Anderson
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Nehora Levi
- Biology Department of Molecular Biology, Faculty of Life Sciences, Ariel University, 40700, Ariel, Israel
| | - Gabi Gerlitz
- Biology Department of Molecular Biology, Faculty of Life Sciences, Ariel University, 40700, Ariel, Israel
| | - Mary C Packard
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Katherine A Dorfman
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Michael Seifu Bahiru
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Andrew D Stephens
- Biology Department, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
- Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
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19
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Riback JA, Eeftens JM, Lee DSW, Quinodoz SA, Donlic A, Orlovsky N, Wiesner L, Beckers L, Becker LA, Strom AR, Rana U, Tolbert M, Purse BW, Kleiner R, Kriwacki R, Brangwynne CP. Viscoelasticity and advective flow of RNA underlies nucleolar form and function. Mol Cell 2023; 83:3095-3107.e9. [PMID: 37683610 PMCID: PMC11089468 DOI: 10.1016/j.molcel.2023.08.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 04/20/2023] [Accepted: 08/08/2023] [Indexed: 09/10/2023]
Abstract
The nucleolus is the largest biomolecular condensate and facilitates transcription, processing, and assembly of ribosomal RNA (rRNA). Although nucleolar function is thought to require multiphase liquid-like properties, nucleolar fluidity and its connection to the highly coordinated transport and biogenesis of ribosomal subunits are poorly understood. Here, we use quantitative imaging, mathematical modeling, and pulse-chase nucleotide labeling to examine nucleolar material properties and rRNA dynamics. The mobility of rRNA is several orders of magnitude slower than that of nucleolar proteins, with rRNA steadily moving away from the transcriptional sites in a slow (∼1 Å/s), radially directed fashion. This constrained but directional mobility, together with polymer physics-based calculations, suggests that nascent rRNA forms an entangled gel, whose constant production drives outward flow. We propose a model in which progressive maturation of nascent rRNA reduces its initial entanglement, fluidizing the nucleolar periphery to facilitate the release of assembled pre-ribosomal particles.
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Affiliation(s)
- Joshua A Riback
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Jorine M Eeftens
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Daniel S W Lee
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, Princeton, NJ 08544, USA
| | - Sofia A Quinodoz
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Anita Donlic
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Natalia Orlovsky
- Department of Molecular Biology, Princeton University, Princeton, Princeton, NJ 08544, USA
| | - Lennard Wiesner
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Lien Beckers
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, Princeton, NJ 08544, USA
| | - Lindsay A Becker
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, Princeton, NJ 08544, USA
| | - Amy R Strom
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Ushnish Rana
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Michele Tolbert
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38103, USA
| | - Byron W Purse
- Department of Chemistry and Biochemistry and the Viral Information Institute, San Diego State University, San Diego, CA 92182, USA
| | - Ralph Kleiner
- Department of Chemistry, Princeton University, Princeton, Princeton, NJ 08544, USA
| | - Richard Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38103, USA
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA; Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, Princeton, NJ 08544, USA; Omenn-Darling Bioengineering Institute, Princeton University, Princeton, NJ 08544, USA.
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20
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Joron K, Viegas JO, Haas-Neill L, Bier S, Drori P, Dvir S, Lim PSL, Rauscher S, Meshorer E, Lerner E. Fluorescent protein lifetimes report densities and phases of nuclear condensates during embryonic stem-cell differentiation. Nat Commun 2023; 14:4885. [PMID: 37573411 PMCID: PMC10423231 DOI: 10.1038/s41467-023-40647-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 08/03/2023] [Indexed: 08/14/2023] Open
Abstract
Fluorescent proteins (FP) are frequently used for studying proteins inside cells. In advanced fluorescence microscopy, FPs can report on additional intracellular variables. One variable is the local density near FPs, which can be useful in studying densities within cellular bio-condensates. Here, we show that a reduction in fluorescence lifetimes of common monomeric FPs reports increased levels of local densities. We demonstrate the use of this fluorescence-based variable to report the distribution of local densities within heterochromatin protein 1α (HP1α) in mouse embryonic stem cells (ESCs), before and after early differentiation. We find that local densities within HP1α condensates in pluripotent ESCs are heterogeneous and cannot be explained by a single liquid phase. Early differentiation, however, induces a change towards a more homogeneous distribution of local densities, which can be explained as a liquid-like phase. In conclusion, we provide a fluorescence-based method to report increased local densities and apply it to distinguish between homogeneous and heterogeneous local densities within bio-condensates.
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Affiliation(s)
- Khalil Joron
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Faculty of Mathematics & Science, The Edmond J. Safra Campus, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Juliane Oliveira Viegas
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel
| | - Liam Haas-Neill
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
- Department of Physics, University of Toronto, Toronto, ON, M5S 1A7, Canada
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
| | - Sariel Bier
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Faculty of Mathematics & Science, The Edmond J. Safra Campus, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel
| | - Paz Drori
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Faculty of Mathematics & Science, The Edmond J. Safra Campus, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Shani Dvir
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Faculty of Mathematics & Science, The Edmond J. Safra Campus, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Patrick Siang Lin Lim
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel
| | - Sarah Rauscher
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
- Department of Physics, University of Toronto, Toronto, ON, M5S 1A7, Canada
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
| | - Eran Meshorer
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
- Edmond and Lily Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
| | - Eitan Lerner
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Faculty of Mathematics & Science, The Edmond J. Safra Campus, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
- The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
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21
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Spicer MFD, Gerlich DW. The material properties of mitotic chromosomes. Curr Opin Struct Biol 2023; 81:102617. [PMID: 37279615 PMCID: PMC10448380 DOI: 10.1016/j.sbi.2023.102617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 03/28/2023] [Accepted: 05/04/2023] [Indexed: 06/08/2023]
Abstract
Chromosomes transform during the cell cycle, allowing transcription and replication during interphase and chromosome segregation during mitosis. Morphological changes are thought to be driven by the combined effects of DNA loop extrusion and a chromatin solubility phase transition. By extruding the chromatin fibre into loops, condensins enrich at an axial core and provide resistance to spindle pulling forces. Mitotic chromosomes are further compacted by deacetylation of histone tails, rendering chromatin insoluble and resistant to penetration by microtubules. Regulation of surface properties by Ki-67 allows independent chromosome movement in early mitosis and clustering during mitotic exit. Recent progress has provided insight into how the extraordinary material properties of chromatin emerge from these activities, and how these properties facilitate faithful chromosome segregation.
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Affiliation(s)
- Maximilian F D Spicer
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), 1030, Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, A-1030, Vienna, Austria. https://twitter.com/Spicer__Max
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), 1030, Vienna, Austria.
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22
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Mirny LA. Chromosome and protein folding: In search for unified principles. Curr Opin Struct Biol 2023; 81:102610. [PMID: 37327690 DOI: 10.1016/j.sbi.2023.102610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 04/24/2023] [Accepted: 04/24/2023] [Indexed: 06/18/2023]
Abstract
Structural biology has traditionally focused on the structures of proteins, short nucleic acids, small molecules, and their complexes. However, it is now widely recognized that the 3D organization of chromosomes should also be included in this list, despite significant differences in scale and complexity of organization. Here we highlight some notable similarities between the folding processes that shape proteins and chromosomes. Both biomolecules are folded by two types of processes: the affinity-mediated interactions, and by active (ATP-dependent) processes. Both chromosome and proteins in vivo can have partially unstructured and non-equilibrium ensembles with yet to be understood functional roles. By analyzing these biological systems in parallel, we can uncover universal principles of biomolecular organization that transcend specific biopolymers.
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Affiliation(s)
- Leonid A Mirny
- Institute for Medical Engineering and Science, and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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23
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Hertzog M, Erdel F. The Material Properties of the Cell Nucleus: A Matter of Scale. Cells 2023; 12:1958. [PMID: 37566037 PMCID: PMC10416959 DOI: 10.3390/cells12151958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/26/2023] [Accepted: 07/26/2023] [Indexed: 08/12/2023] Open
Abstract
Chromatin regulatory processes physically take place in the environment of the cell nucleus, which is filled with the chromosomes and a plethora of smaller biomolecules. The nucleus contains macromolecular assemblies of different sizes, from nanometer-sized protein complexes to micrometer-sized biomolecular condensates, chromosome territories, and nuclear bodies. This multiscale organization impacts the transport processes within the nuclear interior, the global mechanical properties of the nucleus, and the way the nucleus senses and reacts to mechanical stimuli. Here, we discuss recent work on these aspects, including microrheology and micromanipulation experiments assessing the material properties of the nucleus and its subcomponents. We summarize how the properties of multiscale media depend on the time and length scales probed in the experiment, and we reconcile seemingly contradictory observations made on different scales. We also revisit the concept of liquid-like and solid-like material properties for complex media such as the nucleus. We propose that the nucleus can be considered a multiscale viscoelastic medium composed of three major components with distinct properties: the lamina, the chromatin network, and the nucleoplasmic fluid. This multicomponent organization enables the nucleus to serve its different functions as a reaction medium on the nanoscale and as a mechanosensor and structural scaffold on the microscale.
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Affiliation(s)
| | - Fabian Erdel
- MCD, Center for Integrative Biology (CBI), University of Toulouse, CNRS, 169 Avenue Marianne Grunberg-Manago, 31062 Toulouse, France
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24
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Dupont C, Chahar D, Trullo A, Gostan T, Surcis C, Grimaud C, Fisher D, Feil R, Llères D. Evidence for low nanocompaction of heterochromatin in living embryonic stem cells. EMBO J 2023:e110286. [PMID: 37082862 DOI: 10.15252/embj.2021110286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 03/22/2023] [Accepted: 03/29/2023] [Indexed: 04/22/2023] Open
Abstract
Despite advances in the identification of chromatin regulators and genome interactions, the principles of higher-order chromatin structure have remained elusive. Here, we applied FLIM-FRET microscopy to analyse, in living cells, the spatial organisation of nanometre range proximity between nucleosomes, which we called "nanocompaction." Both in naive embryonic stem cells (ESCs) and in ESC-derived epiblast-like cells (EpiLCs), we find that, contrary to expectations, constitutive heterochromatin is much less compacted than bulk chromatin. The opposite was observed in fixed cells. HP1α knockdown increased nanocompaction in living ESCs, but this was overridden by loss of HP1β, indicating the existence of a dynamic HP1-dependent low compaction state in pluripotent cells. Depletion of H4K20me2/3 abrogated nanocompaction, while increased H4K20me3 levels accompanied the nuclear reorganisation during EpiLCs induction. Finally, the knockout of the nuclear cellular-proliferation marker Ki-67 strongly reduced both interphase and mitotic heterochromatin nanocompaction in ESCs. Our data indicate that, contrary to prevailing models, heterochromatin is not highly compacted at the nanoscale but resides in a dynamic low nanocompaction state that depends on H4K20me2/3, the balance between HP1 isoforms, and Ki-67.
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Affiliation(s)
- Claire Dupont
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
| | - Dhanvantri Chahar
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
| | - Antonio Trullo
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
| | - Thierry Gostan
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
| | - Caroline Surcis
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
| | - Charlotte Grimaud
- Institute of Human Genetics (IGH), CNRS, University of Montpellier, Montpellier, France
| | - Daniel Fisher
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
| | - Robert Feil
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
| | - David Llères
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, Montpellier, France
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25
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Kamat K, Lao Z, Qi Y, Wang Y, Ma J, Zhang B. Compartmentalization with nuclear landmarks yields random, yet precise, genome organization. Biophys J 2023; 122:1376-1389. [PMID: 36871158 PMCID: PMC10111368 DOI: 10.1016/j.bpj.2023.03.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 02/19/2023] [Accepted: 03/01/2023] [Indexed: 03/06/2023] Open
Abstract
The 3D organization of eukaryotic genomes plays an important role in genome function. While significant progress has been made in deciphering the folding mechanisms of individual chromosomes, the principles of the dynamic large-scale spatial arrangement of all chromosomes inside the nucleus are poorly understood. We use polymer simulations to model the diploid human genome compartmentalization relative to nuclear bodies such as nuclear lamina, nucleoli, and speckles. We show that a self-organization process based on a cophase separation between chromosomes and nuclear bodies can capture various features of genome organization, including the formation of chromosome territories, phase separation of A/B compartments, and the liquid property of nuclear bodies. The simulated 3D structures quantitatively reproduce both sequencing-based genomic mapping and imaging assays that probe chromatin interaction with nuclear bodies. Importantly, our model captures the heterogeneous distribution of chromosome positioning across cells while simultaneously producing well-defined distances between active chromatin and nuclear speckles. Such heterogeneity and preciseness of genome organization can coexist due to the nonspecificity of phase separation and the slow chromosome dynamics. Together, our work reveals that the cophase separation provides a robust mechanism for us to produce functionally important 3D contacts without requiring thermodynamic equilibration that can be difficult to achieve.
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Affiliation(s)
- Kartik Kamat
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Zhuohan Lao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Yifeng Qi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Yuchuan Wang
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Jian Ma
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Bin Zhang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts.
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26
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Shil S, Tsuruta M, Kawauchi K, Miyoshi D. Biomolecular Liquid-Liquid Phase Separation for Biotechnology. BIOTECH 2023; 12:26. [PMID: 37092470 PMCID: PMC10123627 DOI: 10.3390/biotech12020026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 03/28/2023] [Accepted: 03/30/2023] [Indexed: 04/05/2023] Open
Abstract
The liquid-liquid phase separation (LLPS) of biomolecules induces condensed assemblies called liquid droplets or membrane-less organelles. In contrast to organelles with lipid membrane barriers, the liquid droplets induced by LLPS do not have distinct barriers (lipid bilayer). Biomolecular LLPS in cells has attracted considerable attention in broad research fields from cellular biology to soft matter physics. The physical and chemical properties of LLPS exert a variety of functions in living cells: activating and deactivating biomolecules involving enzymes; controlling the localization, condensation, and concentration of biomolecules; the filtration and purification of biomolecules; and sensing environmental factors for fast, adaptive, and reversible responses. The versatility of LLPS plays an essential role in various biological processes, such as controlling the central dogma and the onset mechanism of pathological diseases. Moreover, biomolecular LLPS could be critical for developing new biotechnologies such as the condensation, purification, and activation of a series of biomolecules. In this review article, we introduce some fundamental aspects and recent progress of biomolecular LLPS in living cells and test tubes. Then, we discuss applications of biomolecular LLPS toward biotechnologies.
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Affiliation(s)
| | | | | | - Daisuke Miyoshi
- Faculty of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, 7-1-20 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Hyogo, Japan
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27
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The HP1α protein is mandatory to repress the circadian clock and its output genes during the 12 h period of transcriptional repression. Proc Natl Acad Sci U S A 2023; 120:e2213075120. [PMID: 36791098 PMCID: PMC9974504 DOI: 10.1073/pnas.2213075120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
The transcriptional repressions driven by the circadian core clock repressors RevErbα, E4BP4, and CRY1/PER1 involve feedback loops which are mandatory for generating the circadian rhythms. These repressors are known to bind to cognate DNA binding sites, but how their circadian bindings trigger the cascade of events leading to these repressions remain to be elucidated. Through molecular and genetic analyses, we now demonstrate that the chromatin protein HP1α plays a key role in these transcriptional repressions of both the circadian clock (CC) genes and their cognate output genes (CCGs). We show that these CC repressors recruit the HP1α protein downstream from a repressive cascade, and that this recruitment is mandatory for the maintenance of both the CC integrity and the expression of the circadian genes. We further show that the presence of HP1α is critical for both the repressor-induced chromatin compaction and the generation of "transcriptionally repressed biomolecular hydrophobic condensates" and demonstrates that HP1α is mandatory within the CC output genes for both the recruitment of DNA methylating enzymes on the intronic deoxyCpG islands and their subsequent methylation.
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28
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de Wit E, Nora EP. New insights into genome folding by loop extrusion from inducible degron technologies. Nat Rev Genet 2023; 24:73-85. [PMID: 36180596 DOI: 10.1038/s41576-022-00530-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2022] [Indexed: 01/24/2023]
Abstract
Chromatin folds into dynamic loops that often span hundreds of kilobases and physically wire distant loci together for gene regulation. These loops are continuously created, extended and positioned by structural maintenance of chromosomes (SMC) protein complexes, such as condensin and cohesin, and their regulators, including CTCF, in a highly dynamic process known as loop extrusion. Genetic loss of extrusion factors is lethal, complicating their study. Inducible protein degradation technologies enable the depletion of loop extrusion factors within hours, leading to the rapid reconfiguration of chromatin folding. Here, we review how these technologies have changed our understanding of genome organization, upsetting long-held beliefs on its role in transcription. Finally, we examine recent models that attempt to reconcile observations after chronic versus acute perturbations, and discuss future developments in this rapidly developing field of research.
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Affiliation(s)
- Elzo de Wit
- Division of Gene Regulation, Oncode Institute, Amsterdam, the Netherlands.
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam, the Netherlands.
| | - Elphège P Nora
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA.
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA.
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29
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Siouda M, Dujardin AD, Dekeyzer B, Schaeffer L, Mulligan P. Chromodomain on Y-like 2 (CDYL2) implicated in mitosis and genome stability regulation via interaction with CHAMP1 and POGZ. Cell Mol Life Sci 2023; 80:47. [PMID: 36658409 PMCID: PMC11072993 DOI: 10.1007/s00018-022-04659-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 11/28/2022] [Accepted: 11/29/2022] [Indexed: 01/21/2023]
Abstract
Histone H3 trimethylation on lysine 9 (H3K9me3) is a defining feature of mammalian pericentromeres, loss of which results in genome instability. Here we show that CDYL2 is recruited to pericentromeres in an H3K9me3-dependent manner and is required for faithful mitosis and genome stability. CDYL2 RNAi in MCF-7 breast cancer cells and Hela cervical cancer cells inhibited their growth, induced apoptosis, and provoked both nuclear and mitotic aberrations. Mass spectrometry analysis of CDYL2-interacting proteins identified the neurodevelopmental disease-linked mitotic regulators CHAMP1 and POGZ, which are associated with a central non-conserved region of CDYL2. RNAi rescue assays identified both the CDYL2 chromodomain and the CHAMP1-POGZ interacting region as required and, together, sufficient for CDYL2 regulation of mitosis and genome stability. CDYL2 RNAi caused loss of CHAMP1 localization at pericentromeres. We propose that CDYL2 functions as an adaptor protein that connects pericentromeric H3K9me3 with CHAMP1 and POGZ to ensure mitotic fidelity and genome stability.
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Affiliation(s)
- Maha Siouda
- Centre Léon Bérard, Cancer Research Center of Lyon, Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Lyon, France
| | - Audrey D Dujardin
- Centre Léon Bérard, Cancer Research Center of Lyon, Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Lyon, France
| | - Blanche Dekeyzer
- Centre Léon Bérard, Cancer Research Center of Lyon, Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Lyon, France
| | - Laurent Schaeffer
- Faculté de Médecine, Physiopathology and Genetics of Neurons and Muscles Division, Institut NeuroMyoGène, Université Claude Bernard Lyon 1, Université de Lyon, INSERM U1217, CNRS, UMR5310, 3ème étage, Aile B, 8 Avenue Rockefeller, 69008, Lyon, France
- Centre de Biotechnologie Cellulaire, CBC Biotec, CHU de Lyon - HCL Groupement Est, 59 Bvd Pinel, 69677, Cedex Bron, France
| | - Peter Mulligan
- Centre Léon Bérard, Cancer Research Center of Lyon, Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Lyon, France.
- Faculté de Médecine, Physiopathology and Genetics of Neurons and Muscles Division, Institut NeuroMyoGène, Université Claude Bernard Lyon 1, Université de Lyon, INSERM U1217, CNRS, UMR5310, 3ème étage, Aile B, 8 Avenue Rockefeller, 69008, Lyon, France.
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30
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Sehgal P, Chaturvedi P. Chromatin and Cancer: Implications of Disrupted Chromatin Organization in Tumorigenesis and Its Diversification. Cancers (Basel) 2023; 15:cancers15020466. [PMID: 36672415 PMCID: PMC9856863 DOI: 10.3390/cancers15020466] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 01/04/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023] Open
Abstract
A hallmark of cancers is uncontrolled cell proliferation, frequently associated with an underlying imbalance in gene expression. This transcriptional dysregulation observed in cancers is multifaceted and involves chromosomal rearrangements, chimeric transcription factors, or altered epigenetic marks. Traditionally, chromatin dysregulation in cancers has been considered a downstream effect of driver mutations. However, here we present a broader perspective on the alteration of chromatin organization in the establishment, diversification, and therapeutic resistance of cancers. We hypothesize that the chromatin organization controls the accessibility of the transcriptional machinery to regulate gene expression in cancerous cells and preserves the structural integrity of the nucleus by regulating nuclear volume. Disruption of this large-scale chromatin in proliferating cancerous cells in conventional chemotherapies induces DNA damage and provides a positive feedback loop for chromatin rearrangements and tumor diversification. Consequently, the surviving cells from these chemotherapies become tolerant to higher doses of the therapeutic reagents, which are significantly toxic to normal cells. Furthermore, the disorganization of chromatin induced by these therapies accentuates nuclear fragility, thereby increasing the invasive potential of these tumors. Therefore, we believe that understanding the changes in chromatin organization in cancerous cells is expected to deliver more effective pharmacological interventions with minimal effects on non-cancerous cells.
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31
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Chiu K, Berrada Y, Eskndir N, Song D, Fong C, Naughton S, Chen T, Moy S, Gyurmey S, James L, Ezeiruaku C, Capistran C, Lowey D, Diwanji V, Peterson S, Parakh H, Burgess AR, Probert C, Zhu A, Anderson B, Levi N, Gerlitz G, Packard MC, Dorfman KA, Bahiru MS, Stephens AD. CTCF is essential for proper mitotic spindle structure and anaphase segregation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.09.523293. [PMID: 36712070 PMCID: PMC9881978 DOI: 10.1101/2023.01.09.523293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Mitosis is an essential process in which the duplicated genome is segregated equally into two daughter cells. CTCF has been reported to be present in mitosis but its importance for mitotic fidelity remains to be determined. To evaluate the importance of CTCF in mitosis, we tracked mitotic behaviors in wild type and two different CTCF CRISPR-based genetic knockdowns. We find that knockdown of CTCF results in prolonged mitoses and failed anaphase segregation via time lapse imaging of SiR-DNA. CTCF knockdown did not alter cell cycling or the mitotic checkpoint, which was activated upon nocodazole treatment. Immunofluorescence imaging of the mitotic spindle in CTCF knockdowns revealed disorganization via tri/tetrapolar spindles and chromosomes behind the spindle pole. Imaging of interphase nuclei showed that nuclear size increased drastically, consistent with failure to divide the duplicated genome in anaphase. Population measurements of nuclear shape in CTCF knockdowns do not display decreased circularity or increased nuclear blebbing relative to wild type. However, failed mitoses do display abnormal nuclear morphologies relative to successful mitoses, suggesting population images do not capture individual behaviors. Thus, CTCF is important for both proper metaphase organization and anaphase segregation which impacts the size and shape of the interphase nucleus.
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Affiliation(s)
- Katherine Chiu
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Yasmin Berrada
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Nebiyat Eskndir
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Dasol Song
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Claire Fong
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Sarah Naughton
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Tina Chen
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Savanna Moy
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Sarah Gyurmey
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Liam James
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Chimere Ezeiruaku
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Caroline Capistran
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Daniel Lowey
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Vedang Diwanji
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Samantha Peterson
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Harshini Parakh
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Ayanna R. Burgess
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Cassandra Probert
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Annie Zhu
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Bryn Anderson
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Nehora Levi
- Biology Department of Molecular Biology, Faculty of Life Sciences, Ariel University, Ariel 40700, Israel
| | - Gabi Gerlitz
- Biology Department of Molecular Biology, Faculty of Life Sciences, Ariel University, Ariel 40700, Israel
| | - Mary C. Packard
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | | | | | - Andrew D. Stephens
- Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA
- Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
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32
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Laghmach R, Malhotra I, Potoyan DA. Multiscale Modeling of Protein-RNA Condensation in and Out of Equilibrium. Methods Mol Biol 2023; 2563:117-133. [PMID: 36227470 DOI: 10.1007/978-1-0716-2663-4_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A vast number of intracellular membraneless bodies also known as biomolecular condensates form through a liquid-liquid phase separation (LLPS) of biomolecules. To date, phase separation has been identified as the main driving force for a membraneless organelles such as nucleoli, Cajal bodies, stress granules, and chromatin compartments. Recently, the protein-RNA condensation is receiving increased attention, because it is closely related to the biological function of cells such as transcription, translation, and RNA metabolism. Despite the multidisciplinary efforts put forth to study the biophysical properties of protein-RNA condensates, there are many fundamental unanswered questions regarding the mechanism of formation and regulation of protein-RNA condensates in eukaryotic cells. Major challenges in studying protein-RNA condensation stem from (i) the molecular heterogeneity and conformational flexibility of RNA and protein chains and (ii) the nonequilibrium nature of transcription and cellular environment. Computer simulations, bioinformatics, and mathematical models are uniquely positioned for shedding light on the microscopic nature of protein-RNA phase separation. To this end, there is an urgent need for innovative models with the right spatiotemporal resolution for confronting the experimental observables in a comprehensive and physics-based manner. In this chapter, we will summarize the currently emerging research efforts, which employ atomistic and coarse-grained molecular models and field theoretical models to understand equilibrium and nonequilibrium aspects of protein-RNA condensation.
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Affiliation(s)
- Rabia Laghmach
- Department of Chemistry, Iowa State University, Ames, IA, USA
| | - Isha Malhotra
- Department of Chemistry, Iowa State University, Ames, IA, USA
| | - Davit A Potoyan
- Department of Chemistry, Iowa State University, Ames, IA, USA.
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33
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Carollo PS, Barra V. Chromatin epigenetics and nuclear lamina keep the nucleus in shape: Examples from natural and accelerated aging. Biol Cell 2023; 115:e2200023. [PMID: 36117150 DOI: 10.1111/boc.202200023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 09/11/2022] [Accepted: 09/12/2022] [Indexed: 01/07/2023]
Abstract
As the repository of genetic information, the cell nucleus must protect DNA integrity from mechanical stresses. The nuclear lamina, which resides within the nuclear envelope (NE), is made up of lamins, intermediate filaments bound to DNA. The nuclear lamina provides the nucleus with the ability to deal with inward as well as outward mechanical stimuli. Chromatin, in turn, through its degrees of compaction, shares this role with the nuclear lamina, thus, ensuring the plasticity of the nucleus. Perturbation of chromatin condensation or the nuclear lamina has been linked to a plethora of biological conditions, that range from cancer and genetic diseases (laminopathies) to aging, both natural and accelerated, such as the case of Hutchinson-Gilford Progeria Syndrome (HGPS). From the experimental results accumulated so far on the topic, a direct link between variations of the epigenetic pattern and nuclear lamina structure would be suggested, however, it has never been clarified thoroughly. This relationship, instead, has a downstream important implication on nucleus shape, genome preservation, force sensing, and, ultimately, aging-related disease onset. With this review, we aim to collect recent studies on the importance of both nuclear lamina components and chromatin status in nuclear mechanics. We also aim to bring to light evidence of the link between DNA methylation and nuclear lamina in natural and accelerated aging.
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Affiliation(s)
- Pietro Salvatore Carollo
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, Palermo, Italy
| | - Viviana Barra
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, Palermo, Italy
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34
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Ballmer D, Tardat M, Ortiz R, Graff-Meyer A, Ozonov E, Genoud C, Peters A, Fanourgakis G. HP1 proteins regulate nucleolar structure and function by secluding pericentromeric constitutive heterochromatin. Nucleic Acids Res 2022; 51:117-143. [PMID: 36533441 PMCID: PMC9841413 DOI: 10.1093/nar/gkac1159] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 10/29/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
Nucleoli are nuclear compartments regulating ribosome biogenesis and cell growth. In embryonic stem cells (ESCs), nucleoli containing transcriptionally active ribosomal genes are spatially separated from pericentromeric satellite repeat sequences packaged in largely repressed constitutive heterochromatin (PCH). To date, mechanisms underlying such nuclear partitioning and the physiological relevance thereof are unknown. Here we show that repressive chromatin at PCH ensures structural integrity and function of nucleoli during cell cycle progression. Loss of heterochromatin proteins HP1α and HP1β causes deformation of PCH, with reduced H3K9 trimethylation (H3K9me3) and HP1γ levels, absence of H4K20me3 and upregulated major satellites expression. Spatially, derepressed PCH aberrantly associates with nucleoli accumulating severe morphological defects during S/G2 cell cycle progression. Hp1α/β deficiency reduces cell proliferation, ribosomal RNA biosynthesis and mobility of Nucleophosmin, a major nucleolar component. Nucleolar integrity and function require HP1α/β proteins to be recruited to H3K9me3-marked PCH and their ability to dimerize. Correspondingly, ESCs deficient for both Suv39h1/2 H3K9 HMTs display similar nucleolar defects. In contrast, Suv4-20h1/2 mutant ESCs lacking H4K20me3 at PCH do not. Suv39h1/2 and Hp1α/β deficiency-induced nucleolar defects are reminiscent of those defining human ribosomopathy disorders. Our results reveal a novel role for SUV39H/HP1-marked repressive constitutive heterochromatin in regulating integrity, function and physiology of nucleoli.
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Affiliation(s)
- Daniel Ballmer
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland,Faculty of Sciences, University of Basel, 4056 Basel, Switzerland
| | - Mathieu Tardat
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Raphael Ortiz
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Alexandra Graff-Meyer
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Evgeniy A Ozonov
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Christel Genoud
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | | | - Grigorios Fanourgakis
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
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35
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Ibrahim Z, Wang T, Destaing O, Salvi N, Hoghoughi N, Chabert C, Rusu A, Gao J, Feletto L, Reynoird N, Schalch T, Zhao Y, Blackledge M, Khochbin S, Panne D. Structural insights into p300 regulation and acetylation-dependent genome organisation. Nat Commun 2022; 13:7759. [PMID: 36522330 PMCID: PMC9755262 DOI: 10.1038/s41467-022-35375-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 11/29/2022] [Indexed: 12/23/2022] Open
Abstract
Histone modifications are deposited by chromatin modifying enzymes and read out by proteins that recognize the modified state. BRD4-NUT is an oncogenic fusion protein of the acetyl lysine reader BRD4 that binds to the acetylase p300 and enables formation of long-range intra- and interchromosomal interactions. We here examine how acetylation reading and writing enable formation of such interactions. We show that NUT contains an acidic transcriptional activation domain that binds to the TAZ2 domain of p300. We use NMR to investigate the structure of the complex and found that the TAZ2 domain has an autoinhibitory role for p300. NUT-TAZ2 interaction or mutations found in cancer that interfere with autoinhibition by TAZ2 allosterically activate p300. p300 activation results in a self-organizing, acetylation-dependent feed-forward reaction that enables long-range interactions by bromodomain multivalent acetyl-lysine binding. We discuss the implications for chromatin organisation, gene regulation and dysregulation in disease.
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Affiliation(s)
- Ziad Ibrahim
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Leicester, UK
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States
| | - Tao Wang
- CNRS UMR 5309, INSERM U1209, Université Grenoble Alpes, Institute for Advanced Biosciences, Grenoble, France
| | - Olivier Destaing
- CNRS UMR 5309, INSERM U1209, Université Grenoble Alpes, Institute for Advanced Biosciences, Grenoble, France
| | - Nicola Salvi
- Institut de Biologie Structurale, CNRS, CEA, UGA, Grenoble, France
| | - Naghmeh Hoghoughi
- CNRS UMR 5309, INSERM U1209, Université Grenoble Alpes, Institute for Advanced Biosciences, Grenoble, France
| | - Clovis Chabert
- CNRS UMR 5309, INSERM U1209, Université Grenoble Alpes, Institute for Advanced Biosciences, Grenoble, France
| | - Alexandra Rusu
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Leicester, UK
| | - Jinjun Gao
- Ben May Department of Cancer Research, The University of Chicago, Chicago, IL, 60637, USA
| | - Leonardo Feletto
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Leicester, UK
| | - Nicolas Reynoird
- CNRS UMR 5309, INSERM U1209, Université Grenoble Alpes, Institute for Advanced Biosciences, Grenoble, France
| | - Thomas Schalch
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Leicester, UK
| | - Yingming Zhao
- Ben May Department of Cancer Research, The University of Chicago, Chicago, IL, 60637, USA
| | | | - Saadi Khochbin
- CNRS UMR 5309, INSERM U1209, Université Grenoble Alpes, Institute for Advanced Biosciences, Grenoble, France
| | - Daniel Panne
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Leicester, UK.
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36
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Mansisidor AR, Risca VI. Chromatin accessibility: methods, mechanisms, and biological insights. Nucleus 2022; 13:236-276. [PMID: 36404679 PMCID: PMC9683059 DOI: 10.1080/19491034.2022.2143106] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/23/2022] [Accepted: 10/30/2022] [Indexed: 11/22/2022] Open
Abstract
Access to DNA is a prerequisite to the execution of essential cellular processes that include transcription, replication, chromosomal segregation, and DNA repair. How the proteins that regulate these processes function in the context of chromatin and its dynamic architectures is an intensive field of study. Over the past decade, genome-wide assays and new imaging approaches have enabled a greater understanding of how access to the genome is regulated by nucleosomes and associated proteins. Additional mechanisms that may control DNA accessibility in vivo include chromatin compaction and phase separation - processes that are beginning to be understood. Here, we review the ongoing development of accessibility measurements, we summarize the different molecular and structural mechanisms that shape the accessibility landscape, and we detail the many important biological functions that are linked to chromatin accessibility.
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Affiliation(s)
- Andrés R. Mansisidor
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
| | - Viviana I. Risca
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
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37
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Currey ML, Kandula V, Biggs R, Marko JF, Stephens AD. A Versatile Micromanipulation Apparatus for Biophysical Assays of the Cell Nucleus. Cell Mol Bioeng 2022; 15:303-312. [PMID: 36119136 PMCID: PMC9474788 DOI: 10.1007/s12195-022-00734-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 08/08/2022] [Indexed: 12/02/2022] Open
Abstract
Intro Force measurements of the nucleus, the strongest organelle, have propelled the field of mechanobiology to understand the basic mechanical components of the nucleus and how these components properly support nuclear morphology and function. Micromanipulation force measurement provides separation of the relative roles of nuclear mechanical components chromatin and lamin A. Methods To provide access to this technique, we have developed a universal micromanipulation apparatus for inverted microscopes. We outline how to engineer and utilize this apparatus through dual micromanipulators, fashion and calibrate micropipettes, and flow systems to isolate a nucleus and provide force vs. extensions measurements. This force measurement approach provides the unique ability to measure the separate contributions of chromatin at short extensions and lamin A strain stiffening at long extensions. We then investigated the apparatus’ controllable and programmable micromanipulators through compression, isolation, and extension in conjunction with fluorescence to develop new assays for nuclear mechanobiology. Results Using this methodology, we provide the first rebuilding of the micromanipulation setup outside of its lab of origin and recapitulate many key findings including spring constant of the nucleus and strain stiffening across many cell types. Furthermore, we have developed new micromanipulation-based techniques to compress nuclei inducing nuclear deformation and/or rupture, track nuclear shape post-isolation, and fluorescence imaging during micromanipulation force measurements. Conclusion We provide the workflow to build and use a micromanipulation apparatus with any inverted microscope to perform nucleus isolation, force measurements, and various other biophysical techniques. Supplementary Information The online version contains supplementary material available at 10.1007/s12195-022-00734-y.
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Affiliation(s)
| | - Viswajit Kandula
- Department of Molecular Biosciences and Department of Physics & Astronomy, Northwestern University, Evanston, USA
- Feinberg School of Medicine, Northwestern University, Chicago, USA
| | - Ronald Biggs
- Department of Molecular Biosciences and Department of Physics & Astronomy, Northwestern University, Evanston, USA
| | - John F. Marko
- Department of Molecular Biosciences and Department of Physics & Astronomy, Northwestern University, Evanston, USA
| | - Andrew D. Stephens
- Biology Department, University of Massachusetts Amherst, Amherst, USA
- Molecular and Cellular Biosciences, University of Massachusetts Amherst, Amherst, USA
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38
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Soranno A, Incicco JJ, De Bona P, Tomko EJ, Galburt EA, Holehouse AS, Galletto R. Shelterin Components Modulate Nucleic Acids Condensation and Phase Separation in the Context of Telomeric DNA. J Mol Biol 2022; 434:167685. [PMID: 35724929 PMCID: PMC9378516 DOI: 10.1016/j.jmb.2022.167685] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 05/26/2022] [Accepted: 06/10/2022] [Indexed: 01/13/2023]
Abstract
Telomeres are nucleoprotein complexes that protect the ends of chromosomes and are essential for chromosome stability in Eukaryotes. In cells, individual telomeres form distinct globules of finite size that appear to be smaller than expected for bare DNA. Moreover, telomeres can cluster together, form telomere-induced-foci or co-localize with promyelocytic leukemia (PML) nuclear bodies. The physical basis for collapse of individual telomeres and coalescence of multiple ones remains unclear, as does the relationship between these two phenomena. By combining single-molecule force spectroscopy measurements, optical microscopy, turbidity assays, and simulations, we show that the telomere scaffolding protein TRF2 can condense individual DNA chains and drives coalescence of multiple DNA molecules, leading to phase separation and the formation of liquid-like droplets. Addition of the TRF2 binding protein hRap1 modulates phase boundaries and tunes the specificity of solution demixing while simultaneously altering the degree of DNA compaction. Our results suggest that the condensation of single telomeres and formation of biomolecular condensates containing multiple telomeres are two different outcomes driven by the same set of molecular interactions. Moreover, binding partners, such as other telomere components, can alter those interactions to promote single-chain DNA compaction over multiple-chain phase separation.
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Affiliation(s)
- Andrea Soranno
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, United States; Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130, United States.
| | - J Jeremías Incicco
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Paolo De Bona
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Eric J Tomko
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Eric A Galburt
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Alex S Holehouse
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, United States; Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130, United States
| | - Roberto Galletto
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, United States.
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39
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Roemer A, Mohammed L, Strickfaden H, Underhill DA, Hendzel MJ. Mechanisms governing the accessibility of DNA damage proteins to constitutive heterochromatin. Front Genet 2022; 13:876862. [PMID: 36092926 PMCID: PMC9458887 DOI: 10.3389/fgene.2022.876862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 07/18/2022] [Indexed: 12/05/2022] Open
Abstract
Chromatin is thought to regulate the accessibility of the underlying DNA sequence to machinery that transcribes and repairs the DNA. Heterochromatin is chromatin that maintains a sufficiently high density of DNA packing to be visible by light microscopy throughout the cell cycle and is thought to be most restrictive to transcription. Several studies have suggested that larger proteins and protein complexes are attenuated in their access to heterochromatin. In addition, heterochromatin domains may be associated with phase separated liquid condensates adding further complexity to the regulation of protein concentration within chromocenters. This provides a solvent environment distinct from the nucleoplasm, and proteins that are not size restricted in accessing this liquid environment may partition between the nucleoplasm and heterochromatin based on relative solubility. In this study, we assessed the accessibility of constitutive heterochromatin in mouse cells, which is organized into large and easily identifiable chromocenters, to fluorescently tagged DNA damage response proteins. We find that proteins larger than the expected 10 nm size limit can access the interior of heterochromatin. We find that the sensor proteins Ku70 and PARP1 enrich in mouse chromocenters. At the same time, MRE11 shows variability within an asynchronous population that ranges from depleted to enriched but is primarily homogeneously distribution between chromocenters and the nucleoplasm. While larger downstream proteins such as ATM, BRCA1, and 53BP1 are commonly depleted in chromocenters, they show a wide range of concentrations, with none being depleted beyond approximately 75%. Contradicting exclusively size-dependent accessibility, many smaller proteins, including EGFP, are also depleted in chromocenters. Our results are consistent with minimal size-dependent selectivity but a distinct solvent environment explaining reduced concentrations of diffusing nucleoplasmic proteins within the volume of the chromocenter.
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40
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Liquid-liquid phase separation in tumor biology. Signal Transduct Target Ther 2022; 7:221. [PMID: 35803926 PMCID: PMC9270353 DOI: 10.1038/s41392-022-01076-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/16/2022] [Accepted: 06/21/2022] [Indexed: 12/12/2022] Open
Abstract
Liquid–liquid phase separation (LLPS) is a novel principle for explaining the precise spatial and temporal regulation in living cells. LLPS compartmentalizes proteins and nucleic acids into micron-scale, liquid-like, membraneless bodies with specific functions, which were recently termed biomolecular condensates. Biomolecular condensates are executors underlying the intracellular spatiotemporal coordination of various biological activities, including chromatin organization, genomic stability, DNA damage response and repair, transcription, and signal transduction. Dysregulation of these cellular processes is a key event in the initiation and/or evolution of cancer, and emerging evidence has linked the formation and regulation of LLPS to malignant transformations in tumor biology. In this review, we comprehensively summarize the detailed mechanisms of biomolecular condensate formation and biophysical function and review the recent major advances toward elucidating the multiple mechanisms involved in cancer cell pathology driven by aberrant LLPS. In addition, we discuss the therapeutic perspectives of LLPS in cancer research and the most recently developed drug candidates targeting LLPS modulation that can be used to combat tumorigenesis.
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41
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Novo CL, Wong EV, Hockings C, Poudel C, Sheekey E, Wiese M, Okkenhaug H, Boulton SJ, Basu S, Walker S, Kaminski Schierle GS, Narlikar GJ, Rugg-Gunn PJ. Satellite repeat transcripts modulate heterochromatin condensates and safeguard chromosome stability in mouse embryonic stem cells. Nat Commun 2022; 13:3525. [PMID: 35725842 PMCID: PMC9209518 DOI: 10.1038/s41467-022-31198-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 06/07/2022] [Indexed: 12/25/2022] Open
Abstract
Heterochromatin maintains genome integrity and function, and is organised into distinct nuclear domains. Some of these domains are proposed to form by phase separation through the accumulation of HP1ɑ. Mouse heterochromatin contains noncoding major satellite repeats (MSR), which are highly transcribed in mouse embryonic stem cells (ESCs). Here, we report that MSR transcripts can drive the formation of HP1ɑ droplets in vitro, and modulate heterochromatin into dynamic condensates in ESCs, contributing to the formation of large nuclear domains that are characteristic of pluripotent cells. Depleting MSR transcripts causes heterochromatin to transition into a more compact and static state. Unexpectedly, changing heterochromatin's biophysical properties has severe consequences for ESCs, including chromosome instability and mitotic defects. These findings uncover an essential role for MSR transcripts in modulating the organisation and properties of heterochromatin to preserve genome stability. They also provide insights into the processes that could regulate phase separation and the functional consequences of disrupting the properties of heterochromatin condensates.
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Affiliation(s)
- Clara Lopes Novo
- Epigenetics Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK.
- Tommy's National Miscarriage Research Centre at Imperial College London, London, W12 0NN, UK.
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
| | - Emily V Wong
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Colin Hockings
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, CB3 0AS, UK
| | - Chetan Poudel
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, CB3 0AS, UK
| | - Eleanor Sheekey
- Epigenetics Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Meike Wiese
- Wellcome - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, CB2 1QR, UK
| | - Hanneke Okkenhaug
- Imaging Facility, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Simon J Boulton
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
- Artios Pharma Ltd., B940, Babraham Research Campus, Cambridge, CB22 3FH, UK
| | - Srinjan Basu
- Wellcome - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, CB2 1QR, UK
| | - Simon Walker
- Imaging Facility, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | | | - Geeta J Narlikar
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Peter J Rugg-Gunn
- Epigenetics Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK.
- Wellcome - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, CB2 1QR, UK.
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42
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Lee DSW, Strom AR, Brangwynne CP. The mechanobiology of nuclear phase separation. APL Bioeng 2022; 6:021503. [PMID: 35540725 PMCID: PMC9054271 DOI: 10.1063/5.0083286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 04/19/2022] [Indexed: 02/06/2023] Open
Abstract
The cell nucleus can be thought of as a complex, dynamic, living material, which functions to organize and protect the genome and coordinate gene expression. These functions are achieved via intricate mechanical and biochemical interactions among its myriad components, including the nuclear lamina, nuclear bodies, and the chromatin itself. While the biophysical organization of the nuclear lamina and chromatin have been thoroughly studied, the concept that liquid–liquid phase separation and related phase transitions play a role in establishing nuclear structure has emerged only recently. Phase transitions are likely to be intimately coupled to the mechanobiology of structural elements in the nucleus, but their interplay with one another is still not understood. Here, we review recent developments on the role of phase separation and mechanics in nuclear organization and discuss the functional implications in cell physiology and disease states.
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Affiliation(s)
- Daniel S. W. Lee
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
| | - Amy R. Strom
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Clifford P. Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
- Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, USA
- Howard Hughes Medical Institute, Princeton University, Princeton, New Jersey 08544, USA
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43
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Gong W, Wee J, Wu MC, Sun X, Li C, Xia K. Persistent spectral simplicial complex-based machine learning for chromosomal structural analysis in cellular differentiation. Brief Bioinform 2022; 23:6583209. [PMID: 35536545 DOI: 10.1093/bib/bbac168] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/12/2022] [Accepted: 03/13/2022] [Indexed: 11/13/2022] Open
Abstract
The three-dimensional (3D) chromosomal structure plays an essential role in all DNA-templated processes, including gene transcription, DNA replication and other cellular processes. Although developing chromosome conformation capture (3C) methods, such as Hi-C, which can generate chromosomal contact data characterized genome-wide chromosomal structural properties, understanding 3D genomic nature-based on Hi-C data remains lacking. Here, we propose a persistent spectral simplicial complex (PerSpectSC) model to describe Hi-C data for the first time. Specifically, a filtration process is introduced to generate a series of nested simplicial complexes at different scales. For each of these simplicial complexes, its spectral information can be calculated from the corresponding Hodge Laplacian matrix. PerSpectSC model describes the persistence and variation of the spectral information of the nested simplicial complexes during the filtration process. Different from all previous models, our PerSpectSC-based features provide a quantitative global-scale characterization of chromosome structures and topology. Our descriptors can successfully classify cell types and also cellular differentiation stages for all the 24 types of chromosomes simultaneously. In particular, persistent minimum best characterizes cell types and Dim (1) persistent multiplicity best characterizes cellular differentiation. These results demonstrate the great potential of our PerSpectSC-based models in polymeric data analysis.
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Affiliation(s)
- Weikang Gong
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China 100124.,Division of Mathematical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - JunJie Wee
- Division of Mathematical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Min-Chun Wu
- Division of Mathematical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Xiaohan Sun
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China 100124
| | - Chunhua Li
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China 100124
| | - Kelin Xia
- Division of Mathematical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
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44
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Meijering AEC, Sarlós K, Nielsen CF, Witt H, Harju J, Kerklingh E, Haasnoot GH, Bizard AH, Heller I, Broedersz CP, Liu Y, Peterman EJG, Hickson ID, Wuite GJL. Nonlinear mechanics of human mitotic chromosomes. Nature 2022; 605:545-550. [PMID: 35508652 PMCID: PMC9117150 DOI: 10.1038/s41586-022-04666-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 03/21/2022] [Indexed: 12/26/2022]
Abstract
In preparation for mitotic cell division, the nuclear DNA of human cells is compacted into individualized, X-shaped chromosomes1. This metamorphosis is driven mainly by the combined action of condensins and topoisomerase IIα (TOP2A)2,3, and has been observed using microscopy for over a century. Nevertheless, very little is known about the structural organization of a mitotic chromosome. Here we introduce a workflow to interrogate the organization of human chromosomes based on optical trapping and manipulation. This allows high-resolution force measurements and fluorescence visualization of native metaphase chromosomes to be conducted under tightly controlled experimental conditions. We have used this method to extensively characterize chromosome mechanics and structure. Notably, we find that under increasing mechanical load, chromosomes exhibit nonlinear stiffening behaviour, distinct from that predicted by classical polymer models4. To explain this anomalous stiffening, we introduce a hierarchical worm-like chain model that describes the chromosome as a heterogeneous assembly of nonlinear worm-like chains. Moreover, through inducible degradation of TOP2A5 specifically in mitosis, we provide evidence that TOP2A has a role in the preservation of chromosome compaction. The methods described here open the door to a wide array of investigations into the structure and dynamics of both normal and disease-associated chromosomes.
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Affiliation(s)
- Anna E C Meijering
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Kata Sarlós
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Christian F Nielsen
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Hannes Witt
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Janni Harju
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Emma Kerklingh
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Guus H Haasnoot
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Anna H Bizard
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Iddo Heller
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Chase P Broedersz
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
| | - Ying Liu
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Erwin J G Peterman
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Ian D Hickson
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark.
| | - Gijs J L Wuite
- Department of Physics and Astronomy and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
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45
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Gurova K. Can aggressive cancers be identified by the "aggressiveness" of their chromatin? Bioessays 2022; 44:e2100212. [PMID: 35452144 DOI: 10.1002/bies.202100212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 04/08/2022] [Accepted: 04/12/2022] [Indexed: 12/15/2022]
Abstract
Phenotypic plasticity is a crucial feature of aggressive cancer, providing the means for cancer progression. Stochastic changes in tumor cell transcriptional programs increase the chances of survival under any condition. I hypothesize that unstable chromatin permits stochastic transitions between transcriptional programs in aggressive cancers and supports non-genetic heterogeneity of tumor cells as a basis for their adaptability. I present a mechanistic model for unstable chromatin which includes destabilized nucleosomes, mobile chromatin fibers and random enhancer-promoter contacts, resulting in stochastic transcription. I suggest potential markers for "unsettled" chromatin in tumors associated with poor prognosis. Although many of the characteristics of unstable chromatin have been described, they were mostly used to explain changes in the transcription of individual genes. I discuss approaches to evaluate the role of unstable chromatin in non-genetic tumor cell heterogeneity and suggest using the degree of chromatin instability and transcriptional noise in tumor cells to predict cancer aggressiveness.
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Affiliation(s)
- Katerina Gurova
- Department of Cell Stress Biology, Roswell Park Comprehensive Cancer Center, Buffalo, New York, USA
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SWI/SNF chromatin remodeler complex within the reward pathway is required for behavioral adaptations to stress. Nat Commun 2022; 13:1807. [PMID: 35379786 PMCID: PMC8980038 DOI: 10.1038/s41467-022-29380-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 02/22/2022] [Indexed: 01/01/2023] Open
Abstract
Enduring behavioral changes upon stress exposure involve changes in gene expression sustained by epigenetic modifications in brain circuits, including the mesocorticolimbic pathway. Brahma (BRM) and Brahma Related Gene 1 (BRG1) are ATPase subunits of the SWI/SNF complexes involved in chromatin remodeling, a process essential to enduring plastic changes in gene expression. Here, we show that in mice, social defeat induces changes in BRG1 nuclear distribution. The inactivation of the Brg1/Smarca4 gene within dopamine-innervated regions or the constitutive inactivation of the Brm/Smarca2 gene leads to resilience to repeated social defeat and decreases the behavioral responses to cocaine without impacting midbrain dopamine neurons activity. Within striatal medium spiny neurons, Brg1 gene inactivation reduces the expression of stress- and cocaine-induced immediate early genes, increases levels of heterochromatin and at a global scale decreases chromatin accessibility. Altogether these data demonstrate the pivotal function of SWI/SNF complexes in behavioral and transcriptional adaptations to salient environmental challenges. Repeated exposure to social stressors in rodents results in behavioural changes. Here the authors show that behavioural adaptations to stress are associated with nuclear organization changes through SWI/SNF chromatin remodeler in specific neuronal populations of the mesolimbic system.
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Janssen SM, Lorincz MC. Interplay between chromatin marks in development and disease. Nat Rev Genet 2022; 23:137-153. [PMID: 34608297 DOI: 10.1038/s41576-021-00416-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2021] [Indexed: 02/07/2023]
Abstract
DNA methylation (DNAme) and histone post-translational modifications (PTMs) have important roles in transcriptional regulation. Although many reports have characterized the functions of such chromatin marks in isolation, recent genome-wide studies reveal surprisingly complex interactions between them. Here, we focus on the interplay between DNAme and methylation of specific lysine residues on the histone H3 tail. We describe the impact of genetic perturbation of the relevant methyltransferases in the mouse on the landscape of chromatin marks as well as the transcriptome. In addition, we discuss the specific neurodevelopmental growth syndromes and cancers resulting from pathogenic mutations in the human orthologues of these genes. Integrating these observations underscores the fundamental importance of crosstalk between DNA and histone H3 methylation in development and disease.
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Affiliation(s)
- Sanne M Janssen
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Matthew C Lorincz
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada.
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48
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Vahabikashi A, Adam SA, Medalia O, Goldman RD. Nuclear lamins: Structure and function in mechanobiology. APL Bioeng 2022; 6:011503. [PMID: 35146235 PMCID: PMC8810204 DOI: 10.1063/5.0082656] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/11/2022] [Indexed: 12/11/2022] Open
Abstract
Nuclear lamins are type V intermediate filament proteins that polymerize into complex filamentous meshworks at the nuclear periphery and in less structured forms throughout the nucleoplasm. Lamins interact with a wide range of nuclear proteins and are involved in numerous nuclear and cellular functions. Within the nucleus, they play roles in chromatin organization and gene regulation, nuclear shape, size, and mechanics, and the organization and anchorage of nuclear pore complexes. At the whole cell level, they are involved in the organization of the cytoskeleton, cell motility, and mechanotransduction. The expression of different lamin isoforms has been associated with developmental progression, differentiation, and tissue-specific functions. Mutations in lamins and their binding proteins result in over 15 distinct human diseases, referred to as laminopathies. The laminopathies include muscular (e.g., Emery-Dreifuss muscular dystrophy and dilated cardiomyopathy), neurological (e.g., microcephaly), and metabolic (e.g., familial partial lipodystrophy) disorders as well as premature aging diseases (e.g., Hutchinson-Gilford Progeria and Werner syndromes). How lamins contribute to the etiology of laminopathies is still unknown. In this review article, we summarize major recent findings on the structure, organization, and multiple functions of lamins in nuclear and more global cellular processes.
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Affiliation(s)
- Amir Vahabikashi
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Stephen A. Adam
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Ohad Medalia
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Robert D. Goldman
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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Rubin J, van Wijnen AJ, Uzer G. Architectural control of mesenchymal stem cell phenotype through nuclear actin. Nucleus 2022; 13:35-48. [PMID: 35133922 PMCID: PMC8837231 DOI: 10.1080/19491034.2022.2029297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There is growing appreciation that architectural components of the nucleus regulate gene accessibility by altering chromatin organization. While nuclear membrane connector proteins link the mechanosensitive actin cytoskeleton to the nucleoskeleton, actin’s contribution to the inner architecture of the nucleus remains enigmatic. Control of actin transport into the nucleus, plus the presence of proteins that control actin structure (the actin tool-box) within the nucleus, suggests that nuclear actin may support biomechanical regulation of gene expression. Cellular actin structure is mechanoresponsive: actin cables generated through forces experienced at the plasma membrane transmit force into the nucleus. We posit that dynamic actin remodeling in response to such biomechanical cues provides a novel level of structural control over the epigenetic landscape. We here propose to bring awareness to the fact that mechanical forces can promote actin transfer into the nucleus and control structural arrangements as illustrated in mesenchymal stem cells, thereby modulating lineage commitment.
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Affiliation(s)
- Janet Rubin
- Department of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Andre J van Wijnen
- Department of Biochemistry, University of Vermont Medical School, Burlington, Vt, USA
| | - Gunes Uzer
- Department of Mechanical & Biomedical Engineering, Boise State University, Boise, ID, USA
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Vertii A. Stress as a Chromatin Landscape Architect. Front Cell Dev Biol 2021; 9:790138. [PMID: 34970548 PMCID: PMC8712864 DOI: 10.3389/fcell.2021.790138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 11/19/2021] [Indexed: 11/16/2022] Open
Abstract
The exponential development of methods investigating different levels of spatial genome organization leads to the appreciation of the chromatin landscape's contribution to gene regulation and cell fate. Multiple levels of 3D chromatin organization include chromatin loops and topologically associated domains, followed by euchromatin and heterochromatin compartments, chromatin domains associated with nuclear bodies, and culminate with the chromosome territories. 3D chromatin architecture is exposed to multiple factors such as cell division and stress, including but not limited to mechanical, inflammatory, and environmental challenges. How exactly the stress exposure shapes the chromatin landscape is a new and intriguing area of research. In this mini-review, the developments that motivate the exploration of this field are discussed.
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Affiliation(s)
- Anastassiia Vertii
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, MA, United States
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