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Magnitov M, de Wit E. Attraction and disruption: how loop extrusion and compartmentalisation shape the nuclear genome. Curr Opin Genet Dev 2024; 86:102194. [PMID: 38636335 DOI: 10.1016/j.gde.2024.102194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 03/21/2024] [Accepted: 03/31/2024] [Indexed: 04/20/2024]
Abstract
Chromatin loops, which bring two distal loci of the same chromosome into close physical proximity, are the ubiquitous units of the three-dimensional genome. Recent advances in understanding the spatial organisation of chromatin suggest that several distinct mechanisms control chromatin interactions, such as loop extrusion by cohesin complexes, compartmentalisation by phase separation, direct protein-protein interactions and others. Here, we review different types of chromatin loops and highlight the factors and processes involved in their regulation. We discuss how loop extrusion and compartmentalisation shape chromatin interactions and how these two processes can either positively or negatively influence each other.
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Affiliation(s)
- Mikhail Magnitov
- Division of Gene Regulation, the Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands. https://twitter.com/@MMagnitov
| | - Elzo de Wit
- Division of Gene Regulation, the Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands.
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2
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Kim J, Wang H, Ercan S. Cohesin mediated loop extrusion from active enhancers form chromatin jets in C. elegans. bioRxiv 2024:2023.09.18.558239. [PMID: 37786717 PMCID: PMC10541618 DOI: 10.1101/2023.09.18.558239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
In mammals, cohesin and CTCF organize the 3D genome into topologically associated domains (TADs) to regulate communication between cis-regulatory elements. However, many organisms, including S. cerevisiae , C. elegans , and A. thaliana lack CTCF. Here, we use C. elegans as a model to investigate the function of cohesin in 3D genome organization in an animal without CTCF. We use auxin-inducible degradation to acutely deplete SMC-3 or its negative regulator WAPL-1 from somatic cells. Using Hi-C data, we identify a cohesin-dependent 3D genome organization feature called chromatin jets (aka fountains). These are population average reflections of DNA loops that are ∼20-40 kb in scale and often cover a few transcribed genes. The jets emerge from NIPBL occupied segments, and the trajectory of the jets coincides with cohesin binding. Cohesin translocation from jet origins depends on a fully intact complex and is extended upon WAPL-1 depletion. Hi-C results support the idea that cohesin is preferentially loaded at NIPBL occupied sites and loop extrudes in an effectively two-sided manner. The location of putative loading sites coincide with active enhancers and the strength of chromatin jet pattern correlates with transcription. Hi-C analyses upon WAPL-1 depletion reveal unequal loop extrusion processivity on each side and stalling due to cohesin molecules colliding. Compared to mammalian systems, average processivity of C. elegans cohesin is ∼10-fold shorter and NIPBL binding does not depend on cohesin. We conclude that the processivity of cohesin scales with genome size; and regardless of CTCF presence, preferential loading of cohesin at enhancers is a conserved mechanism of genome organization that regulates the interaction of gene regulatory elements in 3D.
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3
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Fisher AG. Cell and developmental biology: grand challenges. Front Cell Dev Biol 2024; 12:1377073. [PMID: 38559812 PMCID: PMC10978741 DOI: 10.3389/fcell.2024.1377073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Accepted: 02/19/2024] [Indexed: 04/04/2024] Open
Affiliation(s)
- Amanda G. Fisher
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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4
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Murphy SE, Boettiger AN. Polycomb repression of Hox genes involves spatial feedback but not domain compaction or phase transition. Nat Genet 2024; 56:493-504. [PMID: 38361032 DOI: 10.1038/s41588-024-01661-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 01/10/2024] [Indexed: 02/17/2024]
Abstract
Polycomb group proteins have a critical role in silencing transcription during development. It is commonly proposed that Polycomb-dependent changes in genome folding, which compact chromatin, contribute directly to repression by blocking the binding of activating complexes. Recently, it has also been argued that liquid-liquid demixing of Polycomb proteins facilitates this compaction and repression by phase-separating target genes into a membraneless compartment. To test these models, we used Optical Reconstruction of Chromatin Architecture to trace the Hoxa gene cluster, a canonical Polycomb target, in thousands of single cells. Across multiple cell types, we find that Polycomb-bound chromatin frequently explores decompact states and partial mixing with neighboring chromatin, while remaining uniformly repressed, challenging the repression-by-compaction or phase-separation models. Using polymer simulations, we show that these observed flexible ensembles can be explained by 'spatial feedback'-transient contacts that contribute to the propagation of the epigenetic state (epigenetic memory), without inducing a globular organization.
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Affiliation(s)
- Sedona Eve Murphy
- Department of Genetics, Stanford University, Stanford, CA, USA
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Cell Biology, Yale University, New Haven, CT, USA
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5
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Shao W, Wang J, Zhang Y, Zhang C, Chen J, Chen Y, Fei Z, Ma Z, Sun X, Jiao C. The jet-like chromatin structure defines active secondary metabolism in fungi. Nucleic Acids Res 2024:gkae131. [PMID: 38407438 DOI: 10.1093/nar/gkae131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 02/06/2024] [Accepted: 02/10/2024] [Indexed: 02/27/2024] Open
Abstract
Eukaryotic genomes are spatially organized within the nucleus in a nonrandom manner. However, fungal genome arrangement and its function in development and adaptation remain largely unexplored. Here, we show that the high-order chromosome structure of Fusarium graminearum is sculpted by both H3K27me3 modification and ancient genome rearrangements. Active secondary metabolic gene clusters form a structure resembling chromatin jets. We demonstrate that these jet-like domains, which can propagate symmetrically for 54 kb, are prevalent in the genome and correlate with active gene transcription and histone acetylation. Deletion of GCN5, which encodes a core and functionally conserved histone acetyltransferase, blocks the formation of the domains. Insertion of an exogenous gene within the jet-like domain significantly augments its transcription. These findings uncover an interesting link between alterations in chromatin structure and the activation of fungal secondary metabolism, which could be a general mechanism for fungi to rapidly respond to environmental cues, and highlight the utility of leveraging three-dimensional genome organization in improving gene transcription in eukaryotes.
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Affiliation(s)
- Wenyong Shao
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Jingrui Wang
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Yueqi Zhang
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Chaofan Zhang
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou 311300, Zhejiang, China
| | - Jie Chen
- National Joint Engineering Laboratory of Biopesticide Preparation, College of Forestry and Biotechnology, Zhejiang A&F University, Hangzhou 311300, Zhejiang, China
| | - Yun Chen
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Zhangjun Fei
- Boyce Thompson Institute, Cornell University, Ithaca, NY 14853, USA
| | - Zhonghua Ma
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Xuepeng Sun
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou 311300, Zhejiang, China
| | - Chen Jiao
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China
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6
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Lenz T, Zhang X, Chakraborty A, Ardakany AR, Prudhomme J, Ay F, Deitsch K, Le Roch KG. Chromatin structure and var2csa - a tango in regulation of var gene expression in the human malaria parasite, Plasmodium falciparum? bioRxiv 2024:2024.02.13.580059. [PMID: 38405848 PMCID: PMC10888805 DOI: 10.1101/2024.02.13.580059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Over the last few decades, novel methods have been developed to study how chromosome positioning within the nucleus may play a role in gene regulation. Adaptation of these methods in the human malaria parasite, Plasmodium falciparum, has recently led to the discovery that the three-dimensional structure of chromatin within the nucleus may be critical in controlling expression of virulence genes (var genes). Recent work has implicated an unusual, highly conserved var gene called var2csa in contributing to coordinated transcriptional switching, however how this gene functions in this capacity is unknown. To further understand how var2csa influences var gene switching, targeted DNA double-strand breaks (DSBs) within the sub-telomeric region of chromosome 12 were used to delete the gene and the surrounding chromosomal region. To characterize the changes in chromatin architecture stemming from this deletion and how these changes could affect var gene expression, we used a combination of RNA-seq, Chip-seq and Hi-C to pinpoint epigenetic and chromatin structural modifications in regions of differential gene expression. We observed a net gain of interactions in sub-telomeric regions and internal var gene regions following var2csa knockout, indicating an increase of tightly controlled heterochromatin structures. Our results suggest that disruption of var2csa results not only in changes in var gene transcriptional regulation but also a significant tightening of heterochromatin clusters thereby disrupting coordinated activation of var genes throughout the genome. Altogether our result confirms a strong link between the var2csa locus, chromatin structure and var gene expression.
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Affiliation(s)
- Todd Lenz
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Abhijit Chakraborty
- La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | | | - Jacques Prudhomme
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Ferhat Ay
- La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | - Kirk Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Karine G. Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
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7
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Alonso-Gil D, Losada A. NIPBL and cohesin: new take on a classic tale. Trends Cell Biol 2023; 33:860-871. [PMID: 37062615 DOI: 10.1016/j.tcb.2023.03.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 04/18/2023]
Abstract
Cohesin folds the genome in dynamic chromatin loops and holds the sister chromatids together. NIPBLScc2 is currently considered the cohesin loader, a role that may need reevaluation. NIPBL activates the cohesin ATPase, which is required for topological entrapment of sister DNAs and to fuel DNA loop extrusion, but is not required for chromatin association. Mechanistic dissection of these processes suggests that both NIPBL and the cohesin STAG subunit bind DNA. NIPBL also regulates conformational switches of the complex. Interactions of NIPBL with chromatin factors, including remodelers, replication proteins, and the transcriptional machinery, affect cohesin loading and distribution. Here, we discuss recent research addressing how NIPBL modulates cohesin activities and how its mutation causes a developmental disorder, Cornelia de Lange Syndrome (CdLS).
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Affiliation(s)
- Dácil Alonso-Gil
- Chromosome Dynamics Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Ana Losada
- Chromosome Dynamics Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.
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8
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Raffo A, Paulsen J. The shape of chromatin: insights from computational recognition of geometric patterns in Hi-C data. Brief Bioinform 2023; 24:bbad302. [PMID: 37646128 PMCID: PMC10516369 DOI: 10.1093/bib/bbad302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 07/05/2023] [Accepted: 08/03/2023] [Indexed: 09/01/2023] Open
Abstract
The three-dimensional organization of chromatin plays a crucial role in gene regulation and cellular processes like deoxyribonucleic acid (DNA) transcription, replication and repair. Hi-C and related techniques provide detailed views of spatial proximities within the nucleus. However, data analysis is challenging partially due to a lack of well-defined, underpinning mathematical frameworks. Recently, recognizing and analyzing geometric patterns in Hi-C data has emerged as a powerful approach. This review provides a summary of algorithms for automatic recognition and analysis of geometric patterns in Hi-C data and their correspondence with chromatin structure. We classify existing algorithms on the basis of the data representation and pattern recognition paradigm they make use of. Finally, we outline some of the challenges ahead and promising future directions.
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Affiliation(s)
- Andrea Raffo
- Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Jonas Paulsen
- Department of Biosciences, University of Oslo, 0316 Oslo, Norway
- Centre for Bioinformatics, Department of Informatics, University of Oslo, 0316 Oslo, Norway
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9
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Gil J, Rosin LF, Navarrete E, Chowdhury N, Abraham S, Cornilleau G, Lei EP, Mozziconacci J, Mirny LA, Muller H, Drinnenberg IA. Unique territorial and sub-chromosomal organization revealed in the holocentric moth Bombyx mori. bioRxiv 2023:2023.09.14.557757. [PMID: 37745315 PMCID: PMC10515926 DOI: 10.1101/2023.09.14.557757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
The hallmarks of chromosome organization in multicellular eukaryotes are chromosome territories (CT), chromatin compartments, and different types of domains, including topologically associated domains (TADs). Yet, most of these concepts derive from analyses of organisms with monocentric chromosomes. Here we describe the 3D genome architecture of an organism with holocentric chromosomes, the silkworm Bombyx mori . At the genome-wide scale, B. mori chromosomes form highly separated territories and lack substantial trans contacts. As described in other eukaryotes, B. mori chromosomes segregate into an active A and an inactive B compartment. Remarkably, we also identify a third compartment, Secluded "S", with a unique contact pattern. Compartment S shows strong enrichment of short-range contacts and depletion of long-range contacts. It hosts a unique combination of genetic and epigenetic features, localizes at the periphery of CTs and shows developmental plasticity. Biophysical modeling shows that formation of such secluded domains requires a new mechanism - a high density of extruded loops within them along with low level of extrusion and compartmentalization of A and B. Together with other evidence of loop extrusion in interphase, this suggests SMC-mediated loop extrusion in this insect. Overall, our analyses highlight the evolutionary plasticity of 3D genome organization driven by a new combination of known processes.
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10
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Abstract
Many cellular processes require large-scale rearrangements of chromatin structure. Structural maintenance of chromosomes (SMC) protein complexes are molecular machines that can provide structure to chromatin. These complexes can connect DNA elements in cis, walk along DNA, build and processively enlarge DNA loops and connect DNA molecules in trans to hold together the sister chromatids. These DNA-shaping abilities place SMC complexes at the heart of many DNA-based processes, including chromosome segregation in mitosis, transcription control and DNA replication, repair and recombination. In this Review, we discuss the latest insights into how SMC complexes such as cohesin, condensin and the SMC5-SMC6 complex shape DNA to direct these fundamental chromosomal processes. We also consider how SMC complexes, by building chromatin loops, can counteract the natural tendency of alike chromatin regions to cluster. SMC complexes thus control nuclear organization by participating in a molecular tug of war that determines the architecture of our genome.
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Affiliation(s)
- Claire Hoencamp
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Benjamin D Rowland
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
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11
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Al-Jibury E, King JWD, Guo Y, Lenhard B, Fisher AG, Merkenschlager M, Rueckert D. A deep learning method for replicate-based analysis of chromosome conformation contacts using Siamese neural networks. Nat Commun 2023; 14:5007. [PMID: 37591842 PMCID: PMC10435498 DOI: 10.1038/s41467-023-40547-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Accepted: 07/31/2023] [Indexed: 08/19/2023] Open
Abstract
The organisation of the genome in nuclear space is an important frontier of biology. Chromosome conformation capture methods such as Hi-C and Micro-C produce genome-wide chromatin contact maps that provide rich data containing quantitative and qualitative information about genome architecture. Most conventional approaches to genome-wide chromosome conformation capture data are limited to the analysis of pre-defined features, and may therefore miss important biological information. One constraint is that biologically important features can be masked by high levels of technical noise in the data. Here we introduce a replicate-based method for deep learning from chromatin conformation contact maps. Using a Siamese network configuration our approach learns to distinguish technical noise from biological variation and outperforms image similarity metrics across a range of biological systems. The features extracted from Hi-C maps after perturbation of cohesin and CTCF reflect the distinct biological functions of cohesin and CTCF in the formation of domains and boundaries, respectively. The learnt distance metrics are biologically meaningful, as they mirror the density of cohesin and CTCF binding. These properties make our method a powerful tool for the exploration of chromosome conformation capture data, such as Hi-C capture Hi-C, and Micro-C.
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Affiliation(s)
- Ediem Al-Jibury
- MRC LMS, Imperial College London, London, W12 0NN, UK.
- Department of Computing, Imperial College London, London, SW7 2RH, UK.
| | | | - Ya Guo
- MRC LMS, Imperial College London, London, W12 0NN, UK
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
- WLA Laboratories, Shanghai, 201203, China
| | - Boris Lenhard
- MRC LMS, Imperial College London, London, W12 0NN, UK
- Sars International Centre for Marine Molecular Biology, University of Bergen, 5008, Bergen, Norway
| | | | | | - Daniel Rueckert
- Department of Computing, Imperial College London, London, SW7 2RH, UK.
- Klinikum rechts der Isar, Technical University of Munich, 81675, Munich, Germany.
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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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13
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da Costa-Nunes JA, Noordermeer D. TADs: Dynamic structures to create stable regulatory functions. Curr Opin Struct Biol 2023; 81:102622. [PMID: 37302180 DOI: 10.1016/j.sbi.2023.102622] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/12/2023] [Accepted: 05/15/2023] [Indexed: 06/13/2023]
Abstract
Mammalian chromosomes are organized at different length scales within the cell nucleus. Topologically Associating Domains (TADs) are structural units of 3D genome organization with functions in gene regulation, DNA replication, recombination and repair. Whereas TADs were initially interpreted as insulated domains, recent studies are revealing that these domains should be interpreted as dynamic collections of actively extruding loops. This process of loop extrusion is subsequently blocked at dedicated TAD boundaries, thereby promoting intra-domain interactions over their surroundings. In this review, we discuss how mammalian TAD structure can emerge from this dynamic process and we discuss recent evidence that TAD boundaries can have regulatory functions.
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Affiliation(s)
- José A da Costa-Nunes
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Daan Noordermeer
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
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14
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Corsi F, Rusch E, Goloborodko A. Loop extrusion rules: the next generation. Curr Opin Genet Dev 2023; 81:102061. [PMID: 37354885 DOI: 10.1016/j.gde.2023.102061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 05/12/2023] [Accepted: 05/18/2023] [Indexed: 06/26/2023]
Abstract
The interphase genome of vertebrates contains roughly 100 000 dynamic loops formed by cohesins. These loops are thought to play important roles in many functions, but their exact contribution in each case remains hotly disputed. The key challenge in studying these loops is the lack of a single experimental technique that could reliably and comprehensively visualize their locations and dynamics. Yet, we can infer them using theoretical models that integrate complementary experimental observations. Modeling proved instrumental in showing that cohesins form loops via extrusion. The loop extrusion model made numerous successful qualitative and quantitative predictions and inspired many experiments. However, it also demonstrated limited accuracy in predicting contact maps. Recent research suggests that the original model did not fully account for the intricate details of the mechanism of loop extrusion and its complex regulation. Here, we review the progress in visualizing extrusion and characterizing the cohesin cofactors. These discoveries can be summarized as 'rules' of cohesin movement along chromosomes and incorporated into the next generation of models. Such improved models will enable more accurate inferences of positions and dynamics of cohesin loops and generate better predictions for designing experiments.
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Affiliation(s)
- Flavia Corsi
- Institute of Molecular Biotechnology, Dr. Bohr-Gasse 3, 1030 Vienna, Austria. https://twitter.com/@flavia_corsi
| | - Emma Rusch
- Institute of Molecular Biotechnology, Dr. Bohr-Gasse 3, 1030 Vienna, Austria. https://twitter.com/@emma__rush
| | - Anton Goloborodko
- Institute of Molecular Biotechnology, Dr. Bohr-Gasse 3, 1030 Vienna, Austria.
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15
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Yin Z, Cui S, Xue S, Xie Y, Wang Y, Zhao C, Zhang Z, Wu T, Hou G, Wang W, Xie SQ, Wu Y, Guo Y. Identification of Two Subsets of Subcompartment A1 Associated with High Transcriptional Activity and Frequent Loop Extrusion. Biology (Basel) 2023; 12:1058. [PMID: 37626945 PMCID: PMC10451812 DOI: 10.3390/biology12081058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Revised: 07/24/2023] [Accepted: 07/24/2023] [Indexed: 08/27/2023]
Abstract
Three-dimensional genome organization has been increasingly recognized as an important determinant of the precise regulation of gene expression in mammalian cells, yet the relationship between gene transcriptional activity and spatial subcompartment positioning is still not fully comprehended. Here, we first utilized genome-wide Hi-C data to infer eight types of subcompartment (labeled A1, A2, A3, A4, B1, B2, B3, and B4) in mouse embryonic stem cells and four primary differentiated cell types, including thymocytes, macrophages, neural progenitor cells, and cortical neurons. Transitions of subcompartments may confer gene expression changes in different cell types. Intriguingly, we identified two subsets of subcompartments defined by higher gene density and characterized by strongly looped contact domains, named common A1 and variable A1, respectively. We revealed that common A1, which includes highly expressed genes and abundant housekeeping genes, shows a ~2-fold higher gene density than the variable A1, where cell type-specific genes are significantly enriched. Thus, our study supports a model in which both types of genomic loci with constitutive and regulatory high transcriptional activity can drive the subcompartment A1 formation. Special chromatin subcompartment arrangement and intradomain interactions may, in turn, contribute to maintaining proper levels of gene expression, especially for regulatory non-housekeeping genes.
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Affiliation(s)
- Zihang Yin
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
| | - Shuang Cui
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
| | - Song Xue
- Department of Bioinformatics and Biostatistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China;
| | - Yufan Xie
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
| | - Yefan Wang
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
| | - Chengling Zhao
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
| | - Zhiyu Zhang
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
| | - Tao Wu
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
| | - Guojun Hou
- Shanghai Institute of Rheumatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai 200001, China;
| | - Wuming Wang
- CUHK-SDU Joint Laboratory on Reproductive Genetics, School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China;
| | - Sheila Q. Xie
- MRC London Institute of Medical Sciences, London W12 0NN, UK;
- Institute of Clinical Sciences, Imperial College London, London W12 0NN, UK
| | - Yue Wu
- Department of Bioinformatics and Biostatistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China;
| | - Ya Guo
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; (Z.Y.); (S.C.); (Y.X.); (Y.W.); (C.Z.); (Z.Z.); (T.W.)
- WLA Laboratories, Shanghai 201203, China
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16
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Galitsyna A, Ulianov SV, Bykov NS, Veil M, Gao M, Perevoschikova K, Gelfand M, Razin SV, Mirny L, Onichtchouk D. Extrusion fountains are hallmarks of chromosome organization emerging upon zygotic genome activation. bioRxiv 2023:2023.07.15.549120. [PMID: 37503128 PMCID: PMC10370019 DOI: 10.1101/2023.07.15.549120] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
The first activation of gene expression during development (zygotic genome activation, ZGA) is accompanied by massive changes in chromosome organization. The connection between these two processes remains unknown. Using Hi-C for zebrafish embryos, we found that chromosome folding starts by establishing "fountains", novel elements of chromosome organization, emerging selectively at enhancers upon ZGA. Using polymer simulations, we demonstrate that fountains can emerge as sites of targeted cohesin loading and require two-sided, yet desynchronized, loop extrusion. Specific loss of fountains upon loss of pioneer transcription factors that drive ZGA reveals a causal connection between enhancer activity and fountain formation. Finally, we show that fountains emerge in early Medaka and Xenopus embryos; moreover, we found cohesin-dependent fountain pattern on enhancers of mouse embryonic stem cells. Taken together, fountains are the first enhancer-specific elements of chromosome organization; they constitute starting points of chromosome folding during early development, likely serving as sites of targeted cohesin loading.
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Affiliation(s)
- Aleksandra Galitsyna
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sergey V. Ulianov
- Institute of Gene Biology, Russian Academy of Sciences, 119334, Russia
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Nikolai S. Bykov
- Institute for Information Transmission Problems (the Kharkevich Institute), Russian Academy of Sciences, Moscow, 127051, Russia
- Centro Nacional de Análisis Genómico (CNAG), Baldiri Reixac 4, Barcelona, 08028 Spain
| | - Marina Veil
- Department of Developmental Biology, University of Freiburg, Freiburg, 79104, Germany
| | - Meijiang Gao
- Department of Developmental Biology, University of Freiburg, Freiburg, 79104, Germany
- Signalling Research Centres BIOSS and CIBSS, Freiburg, 79104, Germany
| | - Kristina Perevoschikova
- Faculty of Bioengineering and Bioinformatics, M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Mikhail Gelfand
- Institute for Information Transmission Problems (the Kharkevich Institute), Russian Academy of Sciences, Moscow, 127051, Russia
| | - Sergey V. Razin
- Institute of Gene Biology, Russian Academy of Sciences, 119334, Russia
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Leonid Mirny
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Daria Onichtchouk
- Department of Developmental Biology, University of Freiburg, Freiburg, 79104, Germany
- Signalling Research Centres BIOSS and CIBSS, Freiburg, 79104, Germany
- Koltzov Institute of Developmental Biology RAS, Moscow, 119991, Russia
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17
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Rappoport N, Chomsky E, Nagano T, Seibert C, Lubling Y, Baran Y, Lifshitz A, Leung W, Mukamel Z, Shamir R, Fraser P, Tanay A. Single cell Hi-C identifies plastic chromosome conformations underlying the gastrulation enhancer landscape. Nat Commun 2023; 14:3844. [PMID: 37386027 PMCID: PMC10310791 DOI: 10.1038/s41467-023-39549-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Accepted: 06/19/2023] [Indexed: 07/01/2023] Open
Abstract
Embryonic development involves massive proliferation and differentiation of cell lineages. This must be supported by chromosome replication and epigenetic reprogramming, but how proliferation and cell fate acquisition are balanced in this process is not well understood. Here we use single cell Hi-C to map chromosomal conformations in post-gastrulation mouse embryo cells and study their distributions and correlations with matching embryonic transcriptional atlases. We find that embryonic chromosomes show a remarkably strong cell cycle signature. Despite that, replication timing, chromosome compartment structure, topological associated domains (TADs) and promoter-enhancer contacts are shown to be variable between distinct epigenetic states. About 10% of the nuclei are identified as primitive erythrocytes, showing exceptionally compact and organized compartment structure. The remaining cells are broadly associated with ectoderm and mesoderm identities, showing only mild differentiation of TADs and compartment structures, but more specific localized contacts in hundreds of ectoderm and mesoderm promoter-enhancer pairs. The data suggest that while fully committed embryonic lineages can rapidly acquire specific chromosomal conformations, most embryonic cells are showing plastic signatures driven by complex and intermixed enhancer landscapes.
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Affiliation(s)
- Nimrod Rappoport
- Department of Computer Science and Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
- The Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv, Israel
| | - Elad Chomsky
- Department of Computer Science and Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Takashi Nagano
- Laboratory for Nuclear Dynamics, Institute for Protein Research, Osaka University, Osaka, Japan
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | - Charlie Seibert
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Yaniv Lubling
- Department of Computer Science and Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Yael Baran
- Department of Computer Science and Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Aviezer Lifshitz
- Department of Computer Science and Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Wing Leung
- Laboratory for Nuclear Dynamics, Institute for Protein Research, Osaka University, Osaka, Japan
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | - Zohar Mukamel
- Department of Computer Science and Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Ron Shamir
- The Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv, Israel
| | - Peter Fraser
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK.
- Department of Biological Science, Florida State University, Tallahassee, FL, USA.
| | - Amos Tanay
- Department of Computer Science and Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.
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18
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Chan B, Rubinstein M. Theory of chromatin organization maintained by active loop extrusion. Proc Natl Acad Sci U S A 2023; 120:e2222078120. [PMID: 37253009 PMCID: PMC10266055 DOI: 10.1073/pnas.2222078120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 04/13/2023] [Indexed: 06/01/2023] Open
Abstract
The active loop extrusion hypothesis proposes that chromatin threads through the cohesin protein complex into progressively larger loops until reaching specific boundary elements. We build upon this hypothesis and develop an analytical theory for active loop extrusion which predicts that loop formation probability is a nonmonotonic function of loop length and describes chromatin contact probabilities. We validate our model with Monte Carlo and hybrid Molecular Dynamics-Monte Carlo simulations and demonstrate that our theory recapitulates experimental chromatin conformation capture data. Our results support active loop extrusion as a mechanism for chromatin organization and provide an analytical description of chromatin organization that may be used to specifically modify chromatin contact probabilities.
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Affiliation(s)
- Brian Chan
- Department of Biomedical Engineering, Duke University, Durham, NC27708
| | - Michael Rubinstein
- Department of Biomedical Engineering, Duke University, Durham, NC27708
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC27708
- Department of Chemistry, Duke University, Durham, NC27708
- Department of Physics, Duke University, Durham, NC27708
- Institute for Chemical Reaction Design and Discovery (World Premier International Research Center Initiative-ICReDD), Hokkaido University, Sapporo001-0021, Japan
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19
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Goychuk A, Kannan D, Chakraborty AK, Kardar M. Polymer folding through active processes recreates features of genome organization. Proc Natl Acad Sci U S A 2023; 120:e2221726120. [PMID: 37155885 PMCID: PMC10194017 DOI: 10.1073/pnas.2221726120] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Accepted: 04/02/2023] [Indexed: 05/10/2023] Open
Abstract
From proteins to chromosomes, polymers fold into specific conformations that control their biological function. Polymer folding has long been studied with equilibrium thermodynamics, yet intracellular organization and regulation involve energy-consuming, active processes. Signatures of activity have been measured in the context of chromatin motion, which shows spatial correlations and enhanced subdiffusion only in the presence of adenosine triphosphate. Moreover, chromatin motion varies with genomic coordinate, pointing toward a heterogeneous pattern of active processes along the sequence. How do such patterns of activity affect the conformation of a polymer such as chromatin? We address this question by combining analytical theory and simulations to study a polymer subjected to sequence-dependent correlated active forces. Our analysis shows that a local increase in activity (larger active forces) can cause the polymer backbone to bend and expand, while less active segments straighten out and condense. Our simulations further predict that modest activity differences can drive compartmentalization of the polymer consistent with the patterns observed in chromosome conformation capture experiments. Moreover, segments of the polymer that show correlated active (sub)diffusion attract each other through effective long-ranged harmonic interactions, whereas anticorrelations lead to effective repulsions. Thus, our theory offers nonequilibrium mechanisms for forming genomic compartments, which cannot be distinguished from affinity-based folding using structural data alone. As a first step toward exploring whether active mechanisms contribute to shaping genome conformations, we discuss a data-driven approach.
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Affiliation(s)
- Andriy Goychuk
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Deepti Kannan
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Arup K. Chakraborty
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA02139
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA02139
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard University, Cambridge, MA02139
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Mehran Kardar
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
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20
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Abstract
DNA double-strand breaks (DSBs) occur every cell cycle and must be efficiently repaired. Non-homologous end joining (NHEJ) is the dominant pathway for DSB repair in G1-phase. The first step of NHEJ is to bring the two DSB ends back into proximity (synapsis). Although synapsis is generally assumed to occur through passive diffusion, we show that passive diffusion is unlikely to produce the synapsis speed observed in cells. Instead, we hypothesize that DNA loop extrusion facilitates synapsis. By combining experimentally constrained simulations and theory, we show that a simple loop extrusion model constrained by previous live-cell imaging data only modestly accelerates synapsis. Instead, an expanded loop extrusion model with targeted loading of loop extruding factors (LEFs), a small portion of long-lived LEFs, and LEF stabilization by boundary elements and DSB ends achieves fast synapsis with near 100% efficiency. We propose that loop extrusion contributes to DSB repair by mediating fast synapsis.
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Affiliation(s)
- Jin H Yang
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
- Koch Institute for Integrative Cancer Research, Cambridge, MA, 02142, USA
| | - Hugo B Brandão
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- The Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA.
- Koch Institute for Integrative Cancer Research, Cambridge, MA, 02142, USA.
- Illumina Inc., San Diego, CA, 92122, USA.
| | - Anders S Hansen
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- The Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA.
- Koch Institute for Integrative Cancer Research, Cambridge, MA, 02142, USA.
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21
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Shin H, Kim Y. Regulation of loop extrusion on the interphase genome. Crit Rev Biochem Mol Biol 2023; 58:1-18. [PMID: 36921088 DOI: 10.1080/10409238.2023.2182273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Abstract
In the human cell nucleus, dynamically organized chromatin is the substrate for gene regulation, DNA replication, and repair. A central mechanism of DNA loop formation is an ATPase motor cohesin-mediated loop extrusion. The cohesin complexes load and unload onto the chromosome under the control of other regulators that physically interact and affect motor activity. Regulation of the dynamic loading cycle of cohesin influences not only the chromatin structure but also genome-associated human disorders and aging. This review focuses on the recently spotlighted genome organizing factors and the mechanism by which their dynamic interactions shape the genome architecture in interphase.
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Affiliation(s)
- Hyogyung Shin
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
| | - Yoori Kim
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea.,New Biology Research Center, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
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22
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Drayton JA, Hansen AS. Right on target: Chromatin jets arise from targeted cohesin loading in wild-type cells. Mol Cell 2022; 82:3755-3757. [PMID: 36270244 PMCID: PMC9867926 DOI: 10.1016/j.molcel.2022.09.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 09/27/2022] [Accepted: 09/27/2022] [Indexed: 11/13/2022]
Abstract
Uncovering an informative feature of 3D genome structure, Guo et al. (2022) describe chromatin jets in quiescent murine thymocytes: 1-2 Mb structures formed by targeted cohesin loading at narrow accessible chromatin regions and visible as prominent off-diagonal stripes on contact maps.
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Affiliation(s)
- Jamie A Drayton
- Department of Biological Engineering, Massachusetts Institute of Technology; Cambridge, MA 02139, USA; The Broad Institute of MIT and Harvard; Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research; Cambridge, MA 02139, USA
| | - Anders S Hansen
- Department of Biological Engineering, Massachusetts Institute of Technology; Cambridge, MA 02139, USA; The Broad Institute of MIT and Harvard; Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research; Cambridge, MA 02139, USA.
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