1
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Liu D, Yang J, Cristea IM. Liquid-liquid phase separation in innate immunity. Trends Immunol 2024:S1471-4906(24)00097-8. [PMID: 38762334 DOI: 10.1016/j.it.2024.04.009] [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: 03/18/2024] [Revised: 04/17/2024] [Accepted: 04/24/2024] [Indexed: 05/20/2024]
Abstract
Intrinsic and innate immune responses are essential lines of defense in the body's constant surveillance of pathogens. The discovery of liquid-liquid phase separation (LLPS) as a key regulator of this primal response to infection brings an updated perspective to our understanding of cellular defense mechanisms. Here, we review the emerging multifaceted role of LLPS in diverse aspects of mammalian innate immunity, including DNA and RNA sensing and inflammasome activity. We discuss the intricate regulation of LLPS by post-translational modifications (PTMs), and the subversive tactics used by viruses to antagonize LLPS. This Review, therefore, underscores the significance of LLPS as a regulatory node that offers rapid and plastic control over host immune signaling, representing a promising target for future therapeutic strategies.
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Affiliation(s)
- Dawei Liu
- Department of Molecular Biology, Princeton University; Princeton, NJ 08544, USA
| | - Jinhang Yang
- Department of Molecular Biology, Princeton University; Princeton, NJ 08544, USA
| | - Ileana M Cristea
- Department of Molecular Biology, Princeton University; Princeton, NJ 08544, USA.
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2
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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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3
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Phan TM, Kim YC, Debelouchina GT, Mittal J. Interplay between charge distribution and DNA in shaping HP1 paralog phase separation and localization. eLife 2024; 12:RP90820. [PMID: 38592759 PMCID: PMC11003746 DOI: 10.7554/elife.90820] [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: 04/10/2024] Open
Abstract
The heterochromatin protein 1 (HP1) family is a crucial component of heterochromatin with diverse functions in gene regulation, cell cycle control, and cell differentiation. In humans, there are three paralogs, HP1α, HP1β, and HP1γ, which exhibit remarkable similarities in their domain architecture and sequence properties. Nevertheless, these paralogs display distinct behaviors in liquid-liquid phase separation (LLPS), a process linked to heterochromatin formation. Here, we employ a coarse-grained simulation framework to uncover the sequence features responsible for the observed differences in LLPS. We highlight the significance of the net charge and charge patterning along the sequence in governing paralog LLPS propensities. We also show that both highly conserved folded and less-conserved disordered domains contribute to the observed differences. Furthermore, we explore the potential co-localization of different HP1 paralogs in multicomponent assemblies and the impact of DNA on this process. Importantly, our study reveals that DNA can significantly reshape the stability of a minimal condensate formed by HP1 paralogs due to competitive interactions of HP1α with HP1β and HP1γ versus DNA. In conclusion, our work highlights the physicochemical nature of interactions that govern the distinct phase-separation behaviors of HP1 paralogs and provides a molecular framework for understanding their role in chromatin organization.
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Affiliation(s)
- Tien M Phan
- Artie McFerrin Department of Chemical Engineering, Texas A&M UniversityCollege StationUnited States
| | - Young C Kim
- Center for Materials Physics and Technology, Naval Research LaboratoryWashingtonUnited States
| | - Galia T Debelouchina
- Department of Chemistry and Biochemistry, University of California, San DiegoLa JollaUnited States
| | - Jeetain Mittal
- Artie McFerrin Department of Chemical Engineering, Texas A&M UniversityCollege StationUnited States
- Department of Chemistry, Texas A&M UniversityCollege StationUnited States
- Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M UniversityCollege StationUnited States
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4
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Abasi LS, Elathram N, Movva M, Deep A, Corbett KD, Debelouchina GT. Phosphorylation regulates tau's phase separation behavior and interactions with chromatin. Commun Biol 2024; 7:251. [PMID: 38429335 PMCID: PMC10907630 DOI: 10.1038/s42003-024-05920-4] [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: 12/21/2023] [Accepted: 02/16/2024] [Indexed: 03/03/2024] Open
Abstract
Tau is a microtubule-associated protein often found in neurofibrillary tangles (NFTs) in the brains of patients with Alzheimer's disease. Beyond this context, mounting evidence suggests that tau localizes into the nucleus, where it may play a role in DNA protection and heterochromatin regulation. The molecular mechanisms behind these observations are currently unclear. Using in vitro biophysical experiments, here we demonstrate that tau can undergo liquid-liquid phase separation (LLPS) with DNA, mononucleosomes, and reconstituted nucleosome arrays under low salt conditions. Low concentrations of tau promote chromatin compaction and protect DNA from digestion. While the material state of samples at physiological salt is dominated by chromatin oligomerization, tau can still associate strongly and reversibly with nucleosome arrays. These properties are driven by tau's strong interactions with linker and nucleosomal DNA. In addition, tau co-localizes into droplets formed by nucleosome arrays and phosphorylated HP1α, a key heterochromatin constituent thought to function through an LLPS mechanism. Importantly, LLPS and chromatin interactions are disrupted by aberrant tau hyperphosphorylation. These biophysical properties suggest that tau may directly impact DNA and chromatin accessibility and that loss of these interactions could contribute to the aberrant nuclear effects seen in tau pathology.
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Affiliation(s)
- Lannah S Abasi
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Nesreen Elathram
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Manasi Movva
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Amar Deep
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Kevin D Corbett
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, 92093, USA
- Department of Molecular Biology, University of California San Diego, La Jolla, CA, 92093, USA
| | - Galia T Debelouchina
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, 92093, USA.
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5
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Kapoor U, Kim YC, Mittal J. Coarse-Grained Models to Study Protein-DNA Interactions and Liquid-Liquid Phase Separation. J Chem Theory Comput 2024; 20:1717-1731. [PMID: 37988476 PMCID: PMC10911113 DOI: 10.1021/acs.jctc.3c00525] [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: 05/19/2023] [Revised: 10/20/2023] [Accepted: 10/27/2023] [Indexed: 11/23/2023]
Abstract
Recent advances in coarse-grained (CG) computational models for DNA have enabled molecular-level insights into the behavior of DNA in complex multiscale systems. However, most existing CG DNA models are not compatible with CG protein models, limiting their applications for emerging topics such as protein-nucleic acid assemblies. Here, we present a new computationally efficient CG DNA model. We first use experimental data to establish the model's ability to predict various aspects of DNA behavior, including melting thermodynamics and relevant local structural properties such as the major and minor grooves. We then employ an all-atom hydropathy scale to define nonbonded interactions between protein and DNA sites, to make our DNA model compatible with an existing CG protein model (HPS-Urry), which is extensively used to study protein phase separation, and show that our new model reasonably reproduces the experimental binding affinity for a prototypical protein-DNA system. To further demonstrate the capabilities of this new model, we simulate a full nucleosome with and without histone tails, on a microsecond time scale, generating conformational ensembles and provide molecular insights into the role of histone tails in influencing the liquid-liquid phase separation (LLPS) of HP1α proteins. We find that histone tails interact favorably with DNA, influencing the conformational ensemble of the DNA and antagonizing the contacts between HP1α and DNA, thus affecting the ability of DNA to promote LLPS of HP1α. These findings shed light on the complex molecular framework that fine-tunes the phase transition properties of heterochromatin proteins and contributes to heterochromatin regulation and function. Overall, the CG DNA model presented here is suitable to facilitate micrometer-scale studies with sub-nm resolution in many biological and engineering applications and can be used to investigate protein-DNA complexes, such as nucleosomes, or LLPS of proteins with DNA, enabling a mechanistic understanding of how molecular information may be propagated at the genome level.
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Affiliation(s)
- Utkarsh Kapoor
- Artie
McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 78743, United States
| | - Young C. Kim
- Center
for Materials Physics and Technology, Naval
Research Laboratory, Washington, District of Columbia 20375, United States
| | - Jeetain Mittal
- Artie
McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 78743, United States
- Department
of Chemistry, Texas A&M University, College Station, Texas 78743, United States
- Interdisciplinary
Graduate Program in Genetics in Genomics, Texas A&M University, College
Station, Texas 78743, United States
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6
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Liu Y, Feng W, Wang Y, Wu B. Crosstalk between protein post-translational modifications and phase separation. Cell Commun Signal 2024; 22:110. [PMID: 38347544 PMCID: PMC10860296 DOI: 10.1186/s12964-023-01380-1] [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: 09/15/2023] [Accepted: 11/02/2023] [Indexed: 02/15/2024] Open
Abstract
The phenomenon of phase separation is quite common in cells, and it is involved in multiple processes of life activities. However, the current research on the correlation between protein modifications and phase separation and the interference with the tendency of phase separation has some limitations. Here we focus on several post-translational modifications of proteins, including protein phosphorylation modification at multiple sites, methylation modification, acetylation modification, ubiquitination modification, SUMOylation modification, etc., which regulate the formation of phase separation and the stability of phase separation structure through multivalent interactions. This regulatory role is closely related to the development of neurodegenerative diseases, tumors, viral infections, and other diseases, and also plays essential functions in environmental stress, DNA damage repair, transcriptional regulation, signal transduction, and cell homeostasis of living organisms, which provides an idea to explore the interaction between novel protein post-translational modifications and phase separation. Video Abstract.
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Affiliation(s)
- Yang Liu
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Wenjuan Feng
- Department of Reproductive Medicine, Central Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Yunshan Wang
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China.
- Basic Medical Research Center, Central Hospital Affiliated to Shandong First Medical University, Jinan, China.
| | - Bin Wu
- Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China.
- Department of Reproductive Medicine, Central Hospital Affiliated to Shandong First Medical University, Jinan, China.
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7
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Mohanty P, Rizuan A, Kim YC, Fawzi NL, Mittal J. A complex network of interdomain interactions underlies the conformational ensemble of monomeric TDP-43 and modulates its phase behavior. Protein Sci 2024; 33:e4891. [PMID: 38160320 PMCID: PMC10804676 DOI: 10.1002/pro.4891] [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: 09/06/2023] [Revised: 12/07/2023] [Accepted: 12/28/2023] [Indexed: 01/03/2024]
Abstract
TAR DNA-binding protein 43 (TDP-43) is a multidomain protein involved in the regulation of RNA metabolism, and its aggregates have been observed in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Numerous studies indicate TDP-43 can undergo liquid-liquid phase separation (LLPS) in vitro and is a component of biological condensates. Homo-oligomerization via the folded N-terminal domain (aa:1-77) and the conserved helical region (aa:319-341) of the disordered, C-terminal domain is found to be an important driver of TDP-43 phase separation. However, a comprehensive molecular view of TDP-43 phase separation, particularly regarding the nature of heterodomain interactions, is lacking due to the challenges associated with its stability and purification. Here, we utilize all-atom and coarse-grained (CG) molecular dynamics (MD) simulations to uncover the network of interdomain interactions implicated in TDP-43 phase separation. All-atom simulations uncovered the presence of transient, interdomain interactions involving flexible linkers, RNA-recognition motif (RRM) domains and a charged segment of disordered C-terminal domain (CTD). CG simulations indicate these inter-domain interactions which affect the conformational landscape of TDP-43 in the dilute phase are also prevalent in the condensed phase. Finally, sequence and surface charge distribution analysis coupled with all-atom simulations (at high salt) confirmed that the transient interdomain contacts are predominantly electrostatic in nature. Overall, our findings from multiscale simulations lead to a greater appreciation of the complex interaction network underlying the structural landscape and phase separation of TDP-43.
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Affiliation(s)
- Priyesh Mohanty
- Artie McFerrin Department of Chemical EngineeringTexas A&M UniversityCollege StationTexasUSA
| | - Azamat Rizuan
- Artie McFerrin Department of Chemical EngineeringTexas A&M UniversityCollege StationTexasUSA
| | - Young C. Kim
- Naval Research LaboratoryCenter for Materials Physics and TechnologyWashingtonDistrict of ColumbiaUSA
| | - Nicolas L. Fawzi
- Department of Molecular Biology, Cell Biology and BiochemistryProvidenceRhode IslandUSA
| | - Jeetain Mittal
- Artie McFerrin Department of Chemical EngineeringTexas A&M UniversityCollege StationTexasUSA
- Department of ChemistryTexas A&M UniversityCollege StationTexasUSA
- Interdisciplinary Graduate Program in Genetics and GenomicsTexas A&M UniversityCollege StationTexasUSA
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8
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Ukmar-Godec T, Cima-Omori MS, Yerkesh Z, Eswara K, Yu T, Ramesh R, Riviere G, Ibanez de Opakua A, Fischle W, Zweckstetter M. Multimodal interactions drive chromatin phase separation and compaction. Proc Natl Acad Sci U S A 2023; 120:e2308858120. [PMID: 38048471 PMCID: PMC10723116 DOI: 10.1073/pnas.2308858120] [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: 05/26/2023] [Accepted: 11/01/2023] [Indexed: 12/06/2023] Open
Abstract
Gene silencing is intimately connected to DNA condensation and the formation of transcriptionally inactive heterochromatin by Heterochromatin Protein 1α (HP1α). Because heterochromatin foci are dynamic and HP1α can promote liquid-liquid phase separation, HP1α-mediated phase separation has been proposed as a mechanism of chromatin compaction. The molecular basis of HP1α-driven phase separation and chromatin compaction and the associated regulation by trimethylation of lysine 9 in histone 3 (H3K9me3), which is the hallmark of constitutive heterochromatin, is however largely unknown. Using a combination of chromatin compaction and phase separation assays, site-directed mutagenesis, and NMR-based interaction analysis, we show that human HP1α can compact chromatin in the absence of liquid-liquid phase separation. We further demonstrate that H3K9-trimethylation promotes compaction of chromatin arrays through multimodal interactions. The results provide molecular insights into HP1α-mediated chromatin compaction and thus into the role of human HP1α in the regulation of gene silencing.
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Affiliation(s)
- Tina Ukmar-Godec
- German Center for Neurodegenerative Diseases, Translational Structural Biology, Göttingen37075, Germany
| | - Maria-Sol Cima-Omori
- German Center for Neurodegenerative Diseases, Translational Structural Biology, Göttingen37075, Germany
| | - Zhadyra Yerkesh
- Bioscience Program, Biological and Environmental Science and Engineering Division, Laboratory of Chromatin Biochemistry, King Abdullah University of Science and Technology, Thuwal23955, Saudi Arabia
| | - Karthik Eswara
- Bioscience Program, Biological and Environmental Science and Engineering Division, Laboratory of Chromatin Biochemistry, King Abdullah University of Science and Technology, Thuwal23955, Saudi Arabia
| | - Taekyung Yu
- German Center for Neurodegenerative Diseases, Translational Structural Biology, Göttingen37075, Germany
| | - Reshma Ramesh
- German Center for Neurodegenerative Diseases, Translational Structural Biology, Göttingen37075, Germany
| | - Gwladys Riviere
- German Center for Neurodegenerative Diseases, Translational Structural Biology, Göttingen37075, Germany
| | - Alain Ibanez de Opakua
- German Center for Neurodegenerative Diseases, Translational Structural Biology, Göttingen37075, Germany
| | - Wolfgang Fischle
- Bioscience Program, Biological and Environmental Science and Engineering Division, Laboratory of Chromatin Biochemistry, King Abdullah University of Science and Technology, Thuwal23955, Saudi Arabia
| | - Markus Zweckstetter
- German Center for Neurodegenerative Diseases, Translational Structural Biology, Göttingen37075, Germany
- Department of NMR-based Structural Biology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37077, Germany
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9
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Phan TM, Kim YC, Debelouchina GT, Mittal J. Interplay between charge distribution and DNA in shaping HP1 paralog phase separation and localization. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.28.542535. [PMID: 37398008 PMCID: PMC10312469 DOI: 10.1101/2023.05.28.542535] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The heterochromatin protein 1 (HP1) family is a crucial component of heterochromatin with diverse functions in gene regulation, cell cycle control, and cell differentiation. In humans, there are three paralogs, HP1α, HP1β, and HP1γ, which exhibit remarkable similarities in their domain architecture and sequence properties. Nevertheless, these paralogs display distinct behaviors in liquid-liquid phase separation (LLPS), a process linked to heterochromatin formation. Here, we employ a coarse-grained simulation framework to uncover the sequence features responsible for the observed differences in LLPS. We highlight the significance of the net charge and charge patterning along the sequence in governing paralog LLPS propensities. We also show that both highly conserved folded and less-conserved disordered domains contribute to the observed differences. Furthermore, we explore the potential co-localization of different HP1 paralogs in multicomponent assemblies and the impact of DNA on this process. Importantly, our study reveals that DNA can significantly reshape the stability of a minimal condensate formed by HP1 paralogs due to competitive interactions of HP1α with HP1β and HP1γ versus DNA. In conclusion, our work highlights the physicochemical nature of interactions that govern the distinct phase-separation behaviors of HP1 paralogs and provides a molecular framework for understanding their role in chromatin organization.
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Affiliation(s)
- Tien M. Phan
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, USA
| | - Young C. Kim
- Center for Materials Physics and Technology, Naval Research Laboratory, Washington, DC, USA
| | - Galia T. Debelouchina
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA
| | - Jeetain Mittal
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, USA
- Department of Chemistry, Texas A&M University, College Station, TX, USA
- Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M University, College Station, TX, USA
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10
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Fenton M, Gregory E, Daughdrill G. Protein disorder and autoinhibition: The role of multivalency and effective concentration. Curr Opin Struct Biol 2023; 83:102705. [PMID: 37778184 PMCID: PMC10841074 DOI: 10.1016/j.sbi.2023.102705] [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: 07/15/2023] [Revised: 08/25/2023] [Accepted: 08/28/2023] [Indexed: 10/03/2023]
Abstract
Regulation of protein binding through autoinhibition commonly occurs via interactions involving intrinsically disordered regions (IDRs). These intramolecular interactions can directly or allosterically inhibit intermolecular protein or DNA binding, regulate enzymatic activity, and control the assembly of large macromolecular complexes. Autoinhibitory interactions mediated by protein disorder are inherently transient, making their identification and characterization challenging. In this review, we explore the structural and functional diversity of disorder-mediated autoinhibition for a variety of biological mechanisms, with a focus on the role of multivalency and effective concentration. We also discuss the evolution of disordered motifs that participate in autoinhibition using examples where sequence conservation varies from high to low. In some cases, identifiable motifs that are essential for autoinhibition remain intact within a rapidly evolving sequence, over long evolutionary distances. Finally, we examine the potential of AlphaFold2 to predict autoinhibitory intramolecular interactions involving IDRs.
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Affiliation(s)
- Malissa Fenton
- Department of Molecular Biosciences, University of South Florida, Tampa, FL 33620, USA
| | - Emily Gregory
- Department of Molecular Biosciences, University of South Florida, Tampa, FL 33620, USA
| | - Gary Daughdrill
- Department of Molecular Biosciences, University of South Florida, Tampa, FL 33620, USA.
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11
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Ingólfsson HI, Rizuan A, Liu X, Mohanty P, Souza PCT, Marrink SJ, Bowers MT, Mittal J, Berry J. Multiscale simulations reveal TDP-43 molecular-level interactions driving condensation. Biophys J 2023; 122:4370-4381. [PMID: 37853696 PMCID: PMC10720261 DOI: 10.1016/j.bpj.2023.10.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 05/27/2023] [Accepted: 10/16/2023] [Indexed: 10/20/2023] Open
Abstract
The RNA-binding protein TDP-43 is associated with mRNA processing and transport from the nucleus to the cytoplasm. TDP-43 localizes in the nucleus as well as accumulating in cytoplasmic condensates such as stress granules. Aggregation and formation of amyloid-like fibrils of cytoplasmic TDP-43 are hallmarks of numerous neurodegenerative diseases, most strikingly present in >90% of amyotrophic lateral sclerosis (ALS) patients. If excessive accumulation of cytoplasmic TDP-43 causes, or is caused by, neurodegeneration is presently not known. In this work, we use molecular dynamics simulations at multiple resolutions to explore TDP-43 self- and cross-interaction dynamics. A full-length molecular model of TDP-43, all 414 amino acids, was constructed from select structures of the protein functional domains (N-terminal domain, and two RNA recognition motifs, RRM1 and RRM2) and modeling of disordered connecting loops and the low complexity glycine-rich C-terminus domain. All-atom CHARMM36m simulations of single TDP-43 proteins served as guides to construct a coarse-grained Martini 3 model of TDP-43. The Martini model and a coarser implicit solvent C⍺ model, optimized for disordered proteins, were subsequently used to probe TDP-43 interactions; self-interactions from single-chain full-length TDP-43 simulations, cross-interactions from simulations with two proteins and simulations with assemblies of dozens to hundreds of proteins. Our findings illustrate the utility of different modeling scales for accessing TDP-43 molecular-level interactions and suggest that TDP-43 has numerous interaction preferences or patterns, exhibiting an overall strong, but dynamic, association and driving the formation of biomolecular condensates.
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Affiliation(s)
- Helgi I Ingólfsson
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California.
| | - Azamat Rizuan
- Artie McFerrin Department of Chemical Engineering, Texas A&M College of Engineering, College Station, Texas
| | - Xikun Liu
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California; Department of Chemistry & Biochemistry, University of California Santa Barbara, Santa Barbara, California
| | - Priyesh Mohanty
- Artie McFerrin Department of Chemical Engineering, Texas A&M College of Engineering, College Station, Texas
| | - Paulo C T Souza
- Molecular Microbiology and Structural Biochemistry (MMSB, UMR 5086), CNRS & University of Lyon, Lyon, France; Laboratory of Biology and Modeling of the Cell, École Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5239 and Inserm U1293, 46 Allée d'Italie, Lyon, France
| | - Siewert J Marrink
- Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | - Michael T Bowers
- Department of Chemistry & Biochemistry, University of California Santa Barbara, Santa Barbara, California
| | - Jeetain Mittal
- Artie McFerrin Department of Chemical Engineering, Texas A&M College of Engineering, College Station, Texas; Department of Chemistry, Texas A&M University, College Station, Texas; Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M University, College Station, Texas
| | - Joel Berry
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California
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12
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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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13
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Szała-Mendyk B, Phan TM, Mohanty P, Mittal J. Challenges in studying the liquid-to-solid phase transitions of proteins using computer simulations. Curr Opin Chem Biol 2023; 75:102333. [PMID: 37267850 PMCID: PMC10527940 DOI: 10.1016/j.cbpa.2023.102333] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 04/24/2023] [Accepted: 04/30/2023] [Indexed: 06/04/2023]
Abstract
"Membraneless organelles," also referred to as biomolecular condensates, perform a variety of cellular functions and their dysregulation is implicated in cancer and neurodegeneration. In the last two decades, liquid-liquid phase separation (LLPS) of intrinsically disordered and multidomain proteins has emerged as a plausible mechanism underlying the formation of various biomolecular condensates. Further, the occurrence of liquid-to-solid transitions within liquid-like condensates may give rise to amyloid structures, implying a biophysical link between phase separation and protein aggregation. Despite significant advances, uncovering the microscopic details of liquid-to-solid phase transitions using experiments remains a considerable challenge and presents an exciting opportunity for the development of computational models which provide valuable, complementary insights into the underlying phenomenon. In this review, we first highlight recent biophysical studies which provide new insights into the molecular mechanisms underlying liquid-to-solid (fibril) phase transitions of folded, disordered and multi-domain proteins. Next, we summarize the range of computational models used to study protein aggregation and phase separation. Finally, we discuss recent computational approaches which attempt to capture the underlying physics of liquid-to-solid transitions along with their merits and shortcomings.
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Affiliation(s)
- Beata Szała-Mendyk
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, TAMU 3127, College Station, 77843, Texas, United States.
| | - Tien Minh Phan
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, TAMU 3127, College Station, 77843, Texas, United States.
| | - Priyesh Mohanty
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, TAMU 3127, College Station, 77843, Texas, United States.
| | - Jeetain Mittal
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, TAMU 3127, College Station, 77843, Texas, United States; Department of Chemistry, Texas A&M University, TAMU 3255, College Station, 77843, Texas, United States; Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M University, TAMU 3255, College Station, 77843, Texas, United States.
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14
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Kapoor U, Kim YC, Mittal J. A coarse-grained DNA model to study protein-DNA interactions and liquid-liquid phase separation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.19.541513. [PMID: 37292850 PMCID: PMC10245785 DOI: 10.1101/2023.05.19.541513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Recent advances in coarse-grained (CG) computational models for DNA have enabled molecular-level insights into the behavior of DNA in complex multiscale systems. However, most existing CG DNA models are not compatible with CG protein models, limiting their applications for emerging topics such as protein-nucleic acid assemblies. Here, we present a new computationally efficient CG DNA model. We first use experimental data to establish the model's ability to predict various aspects of DNA behavior, including melting thermodynamics and relevant local structural properties such as the major and minor grooves. We then employ an all-atom hydropathy scale to define non-bonded interactions between protein and DNA sites, to make our DNA model compatible with an existing CG protein model (HPS-Urry), that is extensively used to study protein phase separation, and show that our new model reasonably reproduces the experimental binding affinity for a prototypical protein-DNA system. To further demonstrate the capabilities of this new model, we simulate a full nucleosome with and without histone tails, on a microsecond timescale, generating conformational ensembles and provide molecular insights into the role of histone tails in influencing the liquid-liquid phase separation (LLPS) of HP1α proteins. We find that histone tails interact favorably with DNA, influencing the conformational ensemble of the DNA and antagonizing the contacts between HP1α and DNA, thus affecting the ability of DNA to promote LLPS of HP1α. These findings shed light on the complex molecular framework that fine-tunes the phase transition properties of heterochromatin proteins and contributes to heterochromatin regulation and function. Overall, the CG DNA model presented here is suitable to facilitate micron-scale studies with sub-nm resolution in many biological and engineering applications and can be used to investigate protein-DNA complexes, such as nucleosomes, or LLPS of proteins with DNA, enabling a mechanistic understanding of how molecular information may be propagated at the genome level.
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Affiliation(s)
- Utkarsh Kapoor
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 78743, United States
| | - Young C. Kim
- Center for Materials Physics and Technology, Naval Research Laboratory, Washington, District of Columbia
| | - Jeetain Mittal
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 78743, United States
- Department of Chemistry, Texas A&M University, College Station, Texas 78743, United States
- Interdisciplinary Graduate Program in Genetics in Genomics, Texas A&M University, College Station, Texas 78743, United States
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15
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Vendruscolo M, Fuxreiter M. Towards sequence-based principles for protein phase separation predictions. Curr Opin Chem Biol 2023; 75:102317. [PMID: 37207400 DOI: 10.1016/j.cbpa.2023.102317] [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: 02/06/2023] [Revised: 04/07/2023] [Accepted: 04/11/2023] [Indexed: 05/21/2023]
Abstract
The phenomenon of protein phase separation, which underlies the formation of biomolecular condensates, has been associated with numerous cellular functions. Recent studies indicate that the amino acid sequences of most proteins may harbour not only the code for folding into the native state but also for condensing into the liquid-like droplet state and the solid-like amyloid state. Here we review the current understanding of the principles for sequence-based methods for predicting the propensity of proteins for phase separation. A guiding concept is that entropic contributions are generally more important to stabilise the droplet state than they are for the native and amyloid states. Although estimating these entropic contributions has proven difficult, we describe some progress that has been recently made in this direction. To conclude, we discuss the challenges ahead to extend sequence-based prediction methods of protein phase separation to include quantitative in vivo characterisations of this process.
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Affiliation(s)
- Michele Vendruscolo
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK.
| | - Monika Fuxreiter
- Department of Biomedical Sciences, University of Padova, PD 35131, Italy; Department of Physics and Astronomy, University of Padova, PD 35131, Italy.
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Pavlova I, Iudin M, Surdina A, Severov V, Varizhuk A. G-Quadruplexes in Nuclear Biomolecular Condensates. Genes (Basel) 2023; 14:genes14051076. [PMID: 37239436 DOI: 10.3390/genes14051076] [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: 04/21/2023] [Revised: 05/10/2023] [Accepted: 05/11/2023] [Indexed: 05/28/2023] Open
Abstract
G-quadruplexes (G4s) have long been implicated in the regulation of chromatin packaging and gene expression. These processes require or are accelerated by the separation of related proteins into liquid condensates on DNA/RNA matrices. While cytoplasmic G4s are acknowledged scaffolds of potentially pathogenic condensates, the possible contribution of G4s to phase transitions in the nucleus has only recently come to light. In this review, we summarize the growing evidence for the G4-dependent assembly of biomolecular condensates at telomeres and transcription initiation sites, as well as nucleoli, speckles, and paraspeckles. The limitations of the underlying assays and the remaining open questions are outlined. We also discuss the molecular basis for the apparent permissive role of G4s in the in vitro condensate assembly based on the interactome data. To highlight the prospects and risks of G4-targeting therapies with respect to the phase transitions, we also touch upon the reported effects of G4-stabilizing small molecules on nuclear biomolecular condensates.
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Affiliation(s)
- Iuliia Pavlova
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
| | - Mikhail Iudin
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
| | - Anastasiya Surdina
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
| | - Vjacheslav Severov
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
| | - Anna Varizhuk
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
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17
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Zhang S, Li H, Shen C, Cao F, Kang S. HP1α promotes the progression of prostate cancer. Mol Biol Rep 2023; 50:4459-4468. [PMID: 37014569 DOI: 10.1007/s11033-023-08373-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 03/02/2023] [Indexed: 04/05/2023]
Abstract
PURPOSE Patients who have been diagnosed with prostate cancer (PCa) typically have a dismal outlook and few therapeutic choices available to them, because the precise pathogenesis of the disease is not yet fully understood. The presence of HP1α, also known as the heterochromatin protein 1α, is required for the creation of higher-order chromatin structures. However, little is known about HP1α that serves roles in the pathogenesis of PCa. The primary purpose of our research was to investigate alterations in the levels of HP1α expression and to plan a series of tests to validate the function of HP1α in PCa. METHOD Information on HP1α expression in PCa and benign prostatic hyperplasia (BPH) tissues were gathered using the Cancer Genome Atlas (TCGA) and Gene Expression Profiling Interactive Analysis (GEPIA) databases. RT-qPCR, western blotting, and immunohistochemistry (IHC) were used to assess HP1α mRNA and protein expression in several human PCa tissues and cell lines. The CCK8 assay, clone formation assay, and transwell assay were used to examine biological activities including cell proliferation, migration, and invasion. The expression of proteins connected to apoptosis and the epithelial-mesenchymal transition (EMT) was examined using Western blot. The tumorigenic effect of HP1α was also verified by in vivo experiments. RESULT HP1α expression was much higher in PCa than in BPH tissues and cells, and was positively correlated with the Gleason score of PCa. In vitro experiments showed that HP1α knockdown could inhibit the ability of proliferation, invasion, and migration of PC3 and LNCaP cells, and promote cell apoptosis and EMT. In vivo experiments showed that HP1α knockdown inhibited tumorigenesis in mice. CONCLUSION Our findings indicate that HP1α expression promotes PCa development and might be a novel therapeutic target for the diagnosis or treatment of PCa.
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Affiliation(s)
- Siyang Zhang
- Department of Urology, The Affiliated Taizhou People's Hospital of Nanjing Medical University, Taizhou School of Clinical Medicine, Nanjing Medical University, 366 Taihu Road, 225300, Taizhou, Jiangsu, China.
| | - Hengran Li
- Department of Urology, North China University of Science and Technology Affiliated Hospital, 73 Jianshe South Road, 063000, Tangshan, Hebei, China
| | - Chong Shen
- Department of Urology, The Second Hospital of Tianjin Medical University, 23 Pingjiang road, 300211, Tianjin, China
| | - Fenghong Cao
- Department of Urology, North China University of Science and Technology Affiliated Hospital, 73 Jianshe South Road, 063000, Tangshan, Hebei, China
| | - Shaosan Kang
- Department of Urology, North China University of Science and Technology Affiliated Hospital, 73 Jianshe South Road, 063000, Tangshan, Hebei, China
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18
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Niu X, Zhang L, Wu Y, Zong Z, Wang B, Liu J, Zhang L, Zhou F. Biomolecular condensates: Formation mechanisms, biological functions, and therapeutic targets. MedComm (Beijing) 2023; 4:e223. [PMID: 36875159 PMCID: PMC9974629 DOI: 10.1002/mco2.223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 01/20/2023] [Accepted: 02/02/2023] [Indexed: 03/06/2023] Open
Abstract
Biomolecular condensates are cellular structures composed of membraneless assemblies comprising proteins or nucleic acids. The formation of these condensates requires components to change from a state of solubility separation from the surrounding environment by undergoing phase transition and condensation. Over the past decade, it has become widely appreciated that biomolecular condensates are ubiquitous in eukaryotic cells and play a vital role in physiological and pathological processes. These condensates may provide promising targets for the clinic research. Recently, a series of pathological and physiological processes have been found associated with the dysfunction of condensates, and a range of targets and methods have been demonstrated to modulate the formation of these condensates. A more extensive description of biomolecular condensates is urgently needed for the development of novel therapies. In this review, we summarized the current understanding of biomolecular condensates and the molecular mechanisms of their formation. Moreover, we reviewed the functions of condensates and therapeutic targets for diseases. We further highlighted the available regulatory targets and methods, discussed the significance and challenges of targeting these condensates. Reviewing the latest developments in biomolecular condensate research could be essential in translating our current knowledge on the use of condensates for clinical therapeutic strategies.
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Affiliation(s)
- Xin Niu
- Department of Otolaryngology Head and Neck Surgery The First Affiliated Hospital of Soochow University Suzhou China.,MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network Life Sciences Institute Zhejiang University Hangzhou China
| | - Lei Zhang
- Department of Orthopedics The First Affiliated Hospital of Wenzhou Medical University Wenzhou China
| | - Yuchen Wu
- Department of Clinical Medicine, The First School of Medicine Wenzhou Medical University Wenzhou China
| | - Zhi Zong
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network Life Sciences Institute Zhejiang University Hangzhou China
| | - Bin Wang
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network Life Sciences Institute Zhejiang University Hangzhou China
| | - Jisheng Liu
- Department of Otolaryngology Head and Neck Surgery The First Affiliated Hospital of Soochow University Suzhou China
| | - Long Zhang
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network Life Sciences Institute Zhejiang University Hangzhou China
| | - Fangfang Zhou
- Institutes of Biology and Medical Science Soochow University Suzhou China
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