1
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Guérin TM, Barrington C, Pobegalov G, Molodtsov MI, Uhlmann F. An extrinsic motor directs chromatin loop formation by cohesin. EMBO J 2024; 43:4173-4196. [PMID: 39160275 PMCID: PMC11445435 DOI: 10.1038/s44318-024-00202-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 07/30/2024] [Accepted: 07/31/2024] [Indexed: 08/21/2024] Open
Abstract
The ring-shaped cohesin complex topologically entraps two DNA molecules to establish sister chromatid cohesion. Cohesin also shapes the interphase chromatin landscape with wide-ranging implications for gene regulation, and cohesin is thought to achieve this by actively extruding DNA loops without topologically entrapping DNA. The 'loop extrusion' hypothesis finds motivation from in vitro observations-whether this process underlies in vivo chromatin loop formation remains untested. Here, using the budding yeast S. cerevisiae, we generate cohesin variants that have lost their ability to extrude DNA loops but retain their ability to topologically entrap DNA. Analysis of these variants suggests that in vivo chromatin loops form independently of loop extrusion. Instead, we find that transcription promotes loop formation, and acts as an extrinsic motor that expands these loops and defines their ultimate positions. Our results necessitate a re-evaluation of the loop extrusion hypothesis. We propose that cohesin, akin to sister chromatid cohesion establishment at replication forks, forms chromatin loops by DNA-DNA capture at places of transcription, thus unifying cohesin's two roles in chromosome segregation and interphase genome organisation.
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Affiliation(s)
- Thomas M Guérin
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK
- Université Paris Cité and Université Paris-Saclay, Inserm, CEA, Stabilité Génétique Cellules Souches et Radiations, Fontenay-aux-Roses, France
| | - Christopher Barrington
- Bioinformatics & Biostatistics Science Technology Platform, The Francis Crick Institute, London, UK
| | - Georgii Pobegalov
- Mechanobiology and Biophysics Laboratory, The Francis Crick Institute, London, UK
- Department of Physics and Astronomy, University College London, London, UK
| | - Maxim I Molodtsov
- Mechanobiology and Biophysics Laboratory, The Francis Crick Institute, London, UK
- Department of Physics and Astronomy, University College London, London, UK
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK.
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2
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Liefsoens M, Földes T, Barbi M. Spectral-based detection of chromatin loops in multiplexed super-resolution FISH data. Nat Commun 2024; 15:7670. [PMID: 39237524 PMCID: PMC11377450 DOI: 10.1038/s41467-024-51650-w] [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: 12/11/2023] [Accepted: 08/14/2024] [Indexed: 09/07/2024] Open
Abstract
Involved in mitotic condensation, interaction of transcriptional regulatory elements and isolation of structural domains, loop formation has become a paradigm in the deciphering of chromatin architecture and its functional role. Despite the emergence of increasingly powerful genome visualization techniques, the high variability in cell populations and the randomness of conformations still make loop detection a challenge. We introduce an approach for determining the presence and frequency of loops in a collection of experimental conformations obtained by multiplexed super-resolution imaging. Based on a spectral approach, in conjunction with neural networks, this method offers a powerful tool to detect loops in large experimental data sets, both at the population and single-cell levels. The method's performance is confirmed on experimental FISH data where Hi-C and other loop detection results are available. The method is then applied to recently published experimental data, where it provides a detailed and statistically quantified description of the global architecture of the chromosomal region under study.
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Affiliation(s)
- Michaël Liefsoens
- Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001, Leuven, Belgium.
- LPTMC, Sorbonne Université, CNRS, F-75005, Paris, France.
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium.
| | - Timothy Földes
- LPTMC, Sorbonne Université, CNRS, F-75005, Paris, France.
- Institute for Medical Engineering and Science, MIT, Cambridge, MA, 02139, USA.
| | - Maria Barbi
- LPTMC, Sorbonne Université, CNRS, F-75005, Paris, France
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3
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Moon KW, Kim DG, Ryu JK. Anisotropic scrunching of SMC with a baton-pass mechanism. Commun Biol 2024; 7:881. [PMID: 39030299 PMCID: PMC11271495 DOI: 10.1038/s42003-024-06557-z] [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: 12/18/2023] [Accepted: 07/04/2024] [Indexed: 07/21/2024] Open
Abstract
DNA-loop extrusion is considered to be a universal principle of structural maintenance of chromosome (SMC) proteins with regard to chromosome organization. Despite recent advancements in structural dynamics studies that involve the use of cryogenic-electron microscopy (Cryo-EM), atomic force microscopy (AFM), etc., the precise molecular mechanism underlying DNA-loop extrusion by SMC proteins remains the subject of ongoing discussions. In this context, we propose a scrunching model that incorporates the anisotropic motion of SMC folding with a baton-pass mechanism, offering a potential explanation of how a "DNA baton" is transferred from the hinge domain to a DNA pocket via an anisotropic hinge motion. This proposed model provides insights into how SMC proteins unidirectionally extrude DNA loops in the direction of loop elongation while also maintaining the stability of a DNA loop throughout the dynamic process of DNA-loop extrusion.
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Affiliation(s)
- Kyoung-Wook Moon
- Department of Physics and Astronomy, Seoul National University, Seoul, South Korea
| | - Do-Gyun Kim
- Department of Physics and Astronomy, Seoul National University, Seoul, South Korea
| | - Je-Kyung Ryu
- Department of Physics and Astronomy, Seoul National University, Seoul, South Korea.
- Institute of Applied Physics of Seoul National University, Seoul, South Korea.
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul, South Korea.
- Department of Biological Sciences, Seoul National University, Seoul, South Korea.
- Interdisciplinary Program in Neuroscience, Seoul National University, Seoul, South Korea.
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4
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Cao Z, Wolynes PG. Motorized chain models of the ideal chromosome. Proc Natl Acad Sci U S A 2024; 121:e2407077121. [PMID: 38954553 PMCID: PMC11252987 DOI: 10.1073/pnas.2407077121] [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: 04/08/2024] [Accepted: 06/06/2024] [Indexed: 07/04/2024] Open
Abstract
An array of motor proteins consumes chemical energy in setting up the architectures of chromosomes. Here, we explore how the structure of ideal polymer chains is influenced by two classes of motors. The first class which we call "swimming motors" acts to propel the chromatin fiber through three-dimensional space. They represent a caricature of motors such as RNA polymerases. Previously, they have often been described by adding a persistent flow onto Brownian diffusion of the chain. The second class of motors, which we call "grappling motors" caricatures the loop extrusion processes in which segments of chromatin fibers some distance apart are brought together. We analyze these models using a self-consistent variational phonon approximation to a many-body Master equation incorporating motor activities. We show that whether the swimming motors lead to contraction or expansion depends on the susceptibility of the motors, that is, how their activity depends on the forces they must exert. Grappling motors in contrast to swimming motors lead to long-ranged correlations that resemble those first suggested for fractal globules and that are consistent with the effective interactions inferred by energy landscape analyses of Hi-C data on the interphase chromosome.
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Affiliation(s)
- Zhiyu Cao
- Center for Theoretical Biological Physics, Rice University, Houston, TX77005
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Peter G. Wolynes
- Center for Theoretical Biological Physics, Rice University, Houston, TX77005
- Department of Chemistry, Rice University, Houston, TX77005
- Department of Physics, Rice University, Houston, TX77005
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5
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Xu K, Zhang Y, Baldwin-Brown J, Sasani TA, Phadnis N, Miller MP, Rog O. Decoding chromosome organization using CheC-PLS: chromosome conformation by proximity labeling and long-read sequencing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.31.596864. [PMID: 38895449 PMCID: PMC11185558 DOI: 10.1101/2024.05.31.596864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Genomic approaches have provided detailed insight into chromosome architecture. However, commonly deployed techniques do not preserve connectivity-based information, leaving large-scale genome organization poorly characterized. Here, we developed CheC-PLS: a proximity-labeling technique that indelibly marks, and then decodes, protein-associated sites. CheC-PLS tethers dam methyltransferase to a protein of interest, followed by Nanopore sequencing to identify methylated bases - indicative of in vivo proximity - along reads >100kb. As proof-of-concept we analyzed, in budding yeast, a cohesin-based meiotic backbone that organizes chromatin into an array of loops. Our data recapitulates previously obtained association patterns, and, importantly, exposes variability between cells. Single read data reveals cohesin translocation on DNA and, by anchoring reads onto unique regions, we define the internal organization of the ribosomal DNA locus. Our versatile technique, which we also deployed on isolated nuclei with nanobodies, promises to illuminate diverse chromosomal processes by describing the in vivo conformations of single chromosomes.
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Affiliation(s)
- Kewei Xu
- School of Biological Sciences, University of Utah
- Center for Cell and Genome Sciences, University of Utah
| | - Yichen Zhang
- School of Biological Sciences, University of Utah
- Center for Cell and Genome Sciences, University of Utah
| | | | | | | | | | - Ofer Rog
- School of Biological Sciences, University of Utah
- Center for Cell and Genome Sciences, University of Utah
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6
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Abdennur N, Abraham S, Fudenberg G, Flyamer IM, Galitsyna AA, Goloborodko A, Imakaev M, Oksuz BA, Venev SV, Xiao Y. Cooltools: Enabling high-resolution Hi-C analysis in Python. PLoS Comput Biol 2024; 20:e1012067. [PMID: 38709825 PMCID: PMC11098495 DOI: 10.1371/journal.pcbi.1012067] [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: 10/11/2023] [Revised: 05/16/2024] [Accepted: 04/10/2024] [Indexed: 05/08/2024] Open
Abstract
Chromosome conformation capture (3C) technologies reveal the incredible complexity of genome organization. Maps of increasing size, depth, and resolution are now used to probe genome architecture across cell states, types, and organisms. Larger datasets add challenges at each step of computational analysis, from storage and memory constraints to researchers' time; however, analysis tools that meet these increased resource demands have not kept pace. Furthermore, existing tools offer limited support for customizing analysis for specific use cases or new biology. Here we introduce cooltools (https://github.com/open2c/cooltools), a suite of computational tools that enables flexible, scalable, and reproducible analysis of high-resolution contact frequency data. Cooltools leverages the widely-adopted cooler format which handles storage and access for high-resolution datasets. Cooltools provides a paired command line interface (CLI) and Python application programming interface (API), which respectively facilitate workflows on high-performance computing clusters and in interactive analysis environments. In short, cooltools enables the effective use of the latest and largest genome folding datasets.
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Affiliation(s)
- Open2C
- https://open2c.github.io/
| | - Nezar Abdennur
- Department of Genomics and Computational Biology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Sameer Abraham
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, United States of America
| | - Geoffrey Fudenberg
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, California, United States of America
| | - Ilya M. Flyamer
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Aleksandra A. Galitsyna
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, United States of America
| | - Anton Goloborodko
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Vienna, Austria
| | - Maxim Imakaev
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, United States of America
| | - Betul A. Oksuz
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Sergey V. Venev
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Yao Xiao
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, California, United States of America
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7
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Oberbeckmann E, Oudelaar AM. Genome organization across scales: mechanistic insights from in vitro reconstitution studies. Biochem Soc Trans 2024; 52:793-802. [PMID: 38451192 PMCID: PMC11088924 DOI: 10.1042/bst20230883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 02/19/2024] [Accepted: 02/27/2024] [Indexed: 03/08/2024]
Abstract
Eukaryotic genomes are compacted and organized into distinct three-dimensional (3D) structures, which range from small-scale nucleosome arrays to large-scale chromatin domains. These chromatin structures play an important role in the regulation of transcription and other nuclear processes. The molecular mechanisms that drive the formation of chromatin structures across scales and the relationship between chromatin structure and function remain incompletely understood. Because the processes involved are complex and interconnected, it is often challenging to dissect the underlying principles in the nuclear environment. Therefore, in vitro reconstitution systems provide a valuable approach to gain insight into the molecular mechanisms by which chromatin structures are formed and to determine the cause-consequence relationships between the processes involved. In this review, we give an overview of in vitro approaches that have been used to study chromatin structures across scales and how they have increased our understanding of the formation and function of these structures. We start by discussing in vitro studies that have given insight into the mechanisms of nucleosome positioning. Next, we discuss recent efforts to reconstitute larger-scale chromatin domains and loops and the resulting insights into the principles of genome organization. We conclude with an outlook on potential future applications of chromatin reconstitution systems and how they may contribute to answering open questions concerning chromatin architecture.
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Affiliation(s)
- Elisa Oberbeckmann
- Department of Molecular Biology, Max Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, 37077 Göttingen, Germany
| | - A. Marieke Oudelaar
- Genome Organization and Regulation, Max Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, 37077 Göttingen, Germany
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8
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Golov AK, Gavrilov AA. Cohesin-Dependent Loop Extrusion: Molecular Mechanics and Role in Cell Physiology. BIOCHEMISTRY. BIOKHIMIIA 2024; 89:601-625. [PMID: 38831499 DOI: 10.1134/s0006297924040023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 12/29/2023] [Accepted: 02/15/2024] [Indexed: 06/05/2024]
Abstract
The most prominent representatives of multisubunit SMC complexes, cohesin and condensin, are best known as structural components of mitotic chromosomes. It turned out that these complexes, as well as their bacterial homologues, are molecular motors, the ATP-dependent movement of these complexes along DNA threads leads to the formation of DNA loops. In recent years, we have witnessed an avalanche-like accumulation of data on the process of SMC dependent DNA looping, also known as loop extrusion. This review briefly summarizes the current understanding of the place and role of cohesin-dependent extrusion in cell physiology and presents a number of models describing the potential molecular mechanism of extrusion in a most compelling way. We conclude the review with a discussion of how the capacity of cohesin to extrude DNA loops may be mechanistically linked to its involvement in sister chromatid cohesion.
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Affiliation(s)
- Arkadiy K Golov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
- Technion - Israel Institute of Technology, Haifa, 3525433, Israel
| | - Alexey A Gavrilov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
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9
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Bastié N, Chapard C, Cournac A, Nejmi S, Mboumba H, Gadal O, Thierry A, Beckouët F, Koszul R. Sister chromatid cohesion halts DNA loop expansion. Mol Cell 2024; 84:1139-1148.e5. [PMID: 38452765 DOI: 10.1016/j.molcel.2024.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 12/02/2023] [Accepted: 02/06/2024] [Indexed: 03/09/2024]
Abstract
Eukaryotic genomes are folded into DNA loops mediated by structural maintenance of chromosomes (SMC) complexes such as cohesin, condensin, and Smc5/6. This organization regulates different DNA-related processes along the cell cycle, such as transcription, recombination, segregation, and DNA repair. During the G2 stage, SMC-mediated DNA loops coexist with cohesin complexes involved in sister chromatid cohesion (SCC). However, the articulation between the establishment of SCC and the formation of SMC-mediated DNA loops along the chromatin remains unknown. Here, we show that SCC is indeed a barrier to cohesin-mediated DNA loop expansion along G2/M Saccharomyces cerevisiae chromosomes.
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Affiliation(s)
- Nathalie Bastié
- Molecular, Cellular, and Developmental Biology Department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Christophe Chapard
- Institut Pasteur, CNRS UMR 3525, Université Paris Cité, Unité Régulation Spatiale des Génomes, 75015 Paris, France
| | - Axel Cournac
- Institut Pasteur, CNRS UMR 3525, Université Paris Cité, Unité Régulation Spatiale des Génomes, 75015 Paris, France
| | - Sanae Nejmi
- Cancer Research Centre of Toulouse, INSERM UMR 1037, 31037 Toulouse, France
| | - Henri Mboumba
- Molecular, Cellular, and Developmental Biology Department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Olivier Gadal
- Molecular, Cellular, and Developmental Biology Department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Agnès Thierry
- Institut Pasteur, CNRS UMR 3525, Université Paris Cité, Unité Régulation Spatiale des Génomes, 75015 Paris, France
| | - Frederic Beckouët
- Molecular, Cellular, and Developmental Biology Department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France.
| | - Romain Koszul
- Institut Pasteur, CNRS UMR 3525, Université Paris Cité, Unité Régulation Spatiale des Génomes, 75015 Paris, France.
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10
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Jeppsson K, Pradhan B, Sutani T, Sakata T, Umeda Igarashi M, Berta DG, Kanno T, Nakato R, Shirahige K, Kim E, Björkegren C. Loop-extruding Smc5/6 organizes transcription-induced positive DNA supercoils. Mol Cell 2024; 84:867-882.e5. [PMID: 38295804 DOI: 10.1016/j.molcel.2024.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 11/16/2023] [Accepted: 01/08/2024] [Indexed: 03/10/2024]
Abstract
The structural maintenance of chromosomes (SMC) protein complexes-cohesin, condensin, and the Smc5/6 complex (Smc5/6)-are essential for chromosome function. At the molecular level, these complexes fold DNA by loop extrusion. Accordingly, cohesin creates chromosome loops in interphase, and condensin compacts mitotic chromosomes. However, the role of Smc5/6's recently discovered DNA loop extrusion activity is unknown. Here, we uncover that Smc5/6 associates with transcription-induced positively supercoiled DNA at cohesin-dependent loop boundaries on budding yeast (Saccharomyces cerevisiae) chromosomes. Mechanistically, single-molecule imaging reveals that dimers of Smc5/6 specifically recognize the tip of positively supercoiled DNA plectonemes and efficiently initiate loop extrusion to gather the supercoiled DNA into a large plectonemic loop. Finally, Hi-C analysis shows that Smc5/6 links chromosomal regions containing transcription-induced positive supercoiling in cis. Altogether, our findings indicate that Smc5/6 controls the three-dimensional organization of chromosomes by recognizing and initiating loop extrusion on positively supercoiled DNA.
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Affiliation(s)
- Kristian Jeppsson
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden; Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden; Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
| | - Biswajit Pradhan
- Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Takashi Sutani
- Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Toyonori Sakata
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden; Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden; Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Miki Umeda Igarashi
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden; Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden
| | - Davide Giorgio Berta
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden
| | - Takaharu Kanno
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden; Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden
| | - Ryuichiro Nakato
- Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Katsuhiko Shirahige
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden; Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden; Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Eugene Kim
- Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
| | - Camilla Björkegren
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden; Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden.
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11
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Oberbeckmann E, Quililan K, Cramer P, Oudelaar AM. In vitro reconstitution of chromatin domains shows a role for nucleosome positioning in 3D genome organization. Nat Genet 2024; 56:483-492. [PMID: 38291333 PMCID: PMC10937381 DOI: 10.1038/s41588-023-01649-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 12/15/2023] [Indexed: 02/01/2024]
Abstract
Eukaryotic genomes are organized into chromatin domains. The molecular mechanisms driving the formation of these domains are difficult to dissect in vivo and remain poorly understood. Here we reconstitute Saccharomyces cerevisiae chromatin in vitro and determine its 3D organization at subnucleosome resolution by micrococcal nuclease-based chromosome conformation capture and molecular dynamics simulations. We show that regularly spaced and phased nucleosome arrays form chromatin domains in vitro that resemble domains in vivo. This demonstrates that neither loop extrusion nor transcription is required for basic domain formation in yeast. In addition, we find that the boundaries of reconstituted domains correspond to nucleosome-free regions and that insulation strength scales with their width. Finally, we show that domain compaction depends on nucleosome linker length, with longer linkers forming more compact structures. Together, our results demonstrate that regular nucleosome positioning is important for the formation of chromatin domains and provide a proof-of-principle for bottom-up 3D genome studies.
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Affiliation(s)
- Elisa Oberbeckmann
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany.
| | - Kimberly Quililan
- Max Planck Institute for Multidisciplinary Sciences, Genome Organization and Regulation, Göttingen, Germany
- The Francis Crick Institute, London, UK
| | - Patrick Cramer
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - A Marieke Oudelaar
- Max Planck Institute for Multidisciplinary Sciences, Genome Organization and Regulation, Göttingen, Germany.
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12
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Poinsignon T, Gallopin M, Grognet P, Malagnac F, Lelandais G, Poulain P. 3D models of fungal chromosomes to enhance visual integration of omics data. NAR Genom Bioinform 2023; 5:lqad104. [PMID: 38058589 PMCID: PMC10696920 DOI: 10.1093/nargab/lqad104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 10/11/2023] [Accepted: 11/17/2023] [Indexed: 12/08/2023] Open
Abstract
The functions of eukaryotic chromosomes and their spatial architecture in the nucleus are reciprocally dependent. Hi-C experiments are routinely used to study chromosome 3D organization by probing chromatin interactions. Standard representation of the data has relied on contact maps that show the frequency of interactions between parts of the genome. In parallel, it has become easier to build 3D models of the entire genome based on the same Hi-C data, and thus benefit from the methodology and visualization tools developed for structural biology. 3D modeling of entire genomes leverages the understanding of their spatial organization. However, this opportunity for original and insightful modeling is underexploited. In this paper, we show how seeing the spatial organization of chromosomes can bring new perspectives to omics data integration. We assembled state-of-the-art tools into a workflow that goes from Hi-C raw data to fully annotated 3D models and we re-analysed public omics datasets available for three fungal species. Besides the well-described properties of the spatial organization of their chromosomes (Rabl conformation, hypercoiling and chromosome territories), our results highlighted (i) in Saccharomyces cerevisiae, the backbones of the cohesin anchor regions, which were aligned all along the chromosomes, (ii) in Schizosaccharomyces pombe, the oscillations of the coiling of chromosome arms throughout the cell cycle and (iii) in Neurospora crassa, the massive relocalization of histone marks in mutants of heterochromatin regulators. 3D modeling of the chromosomes brings new opportunities for visual integration of omics data. This holistic perspective supports intuition and lays the foundation for building new concepts.
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Affiliation(s)
- Thibault Poinsignon
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Mélina Gallopin
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Pierre Grognet
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Fabienne Malagnac
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Gaëlle Lelandais
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Pierre Poulain
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
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13
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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: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [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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14
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Borrie MS, Kraycer PM, Gartenberg MR. Transcription-Driven Translocation of Cohesive and Non-Cohesive Cohesin In Vivo. Mol Cell Biol 2023; 43:254-268. [PMID: 37178128 PMCID: PMC10251789 DOI: 10.1080/10985549.2023.2199660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 03/23/2023] [Accepted: 03/28/2023] [Indexed: 05/15/2023] Open
Abstract
Cohesin is a central architectural element of chromosomes that regulates numerous DNA-based events. The complex holds sister chromatids together until anaphase onset and organizes individual chromosomal DNAs into loops and self-associating domains. Purified cohesin diffuses along DNA in an ATP-independent manner but can be propelled by transcribing RNA polymerase. In conjunction with a cofactor, the complex also extrudes DNA loops in an ATP-dependent manner. In this study we examine transcription-driven translocation of cohesin under various conditions in yeast. To this end, obstacles of increasing size were tethered to DNA to act as roadblocks to complexes mobilized by an inducible gene. The obstacles were built from a GFP-lacI core fused to one or more mCherries. A chimera with four mCherries blocked cohesin passage in late G1. During M phase, the threshold barrier depended on the state of cohesion: non-cohesive complexes were also blocked by four mCherries whereas cohesive complexes were blocked by as few as three mCherries. Furthermore cohesive complexes that were stalled at obstacles, in turn, blocked the passage of non-cohesive complexes. That synthetic barriers capture mobilized cohesin demonstrates that transcription-driven complexes translocate processively in vivo. Together, this study reveals unexplored limitations to cohesin movement on chromosomes.
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Affiliation(s)
- Melinda S. Borrie
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Paul M. Kraycer
- Graduate Program in Cellular and Molecular Pharmacology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Marc R. Gartenberg
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
- Member of The Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
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15
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Hill L, Wutz G, Jaritz M, Tagoh H, Calderón L, Peters JM, Goloborodko A, Busslinger M. Igh and Igk loci use different folding principles for V gene recombination due to distinct chromosomal architectures of pro-B and pre-B cells. Nat Commun 2023; 14:2316. [PMID: 37085514 PMCID: PMC10121685 DOI: 10.1038/s41467-023-37994-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 04/04/2023] [Indexed: 04/23/2023] Open
Abstract
Extended loop extrusion across the immunoglobulin heavy-chain (Igh) locus facilitates VH-DJH recombination following downregulation of the cohesin-release factor Wapl by Pax5, resulting in global changes in the chromosomal architecture of pro-B cells. Here, we demonstrate that chromatin looping and VK-JK recombination at the Igk locus were insensitive to Wapl upregulation in pre-B cells. Notably, the Wapl protein was expressed at a 2.2-fold higher level in pre-B cells compared with pro-B cells, which resulted in a distinct chromosomal architecture with normal loop sizes in pre-B cells. High-resolution chromosomal contact analysis of the Igk locus identified multiple internal loops, which likely juxtapose VK and JK elements to facilitate VK-JK recombination. The higher Wapl expression in Igμ-transgenic pre-B cells prevented extended loop extrusion at the Igh locus, leading to recombination of only the 6 most 3' proximal VH genes and likely to allelic exclusion of all other VH genes in pre-B cells. These results suggest that pro-B and pre-B cells with their distinct chromosomal architectures use different chromatin folding principles for V gene recombination, thereby enabling allelic exclusion at the Igh locus, when the Igk locus is recombined.
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Affiliation(s)
- Louisa Hill
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, A-1030, Vienna, Austria
| | - Gordana Wutz
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, A-1030, Vienna, Austria
| | - Markus Jaritz
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, A-1030, Vienna, Austria
| | - Hiromi Tagoh
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, A-1030, Vienna, Austria
| | - Lesly Calderón
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, A-1030, Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, A-1030, Vienna, Austria
| | - Anton Goloborodko
- Institute of Molecular Biotechnology (IMBA), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, A-1030, Vienna, Austria
| | - Meinrad Busslinger
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, A-1030, Vienna, Austria.
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16
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Hu Y, Stillman B. Origins of DNA replication in eukaryotes. Mol Cell 2023; 83:352-372. [PMID: 36640769 PMCID: PMC9898300 DOI: 10.1016/j.molcel.2022.12.024] [Citation(s) in RCA: 45] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 01/15/2023]
Abstract
Errors occurring during DNA replication can result in inaccurate replication, incomplete replication, or re-replication, resulting in genome instability that can lead to diseases such as cancer or disorders such as autism. A great deal of progress has been made toward understanding the entire process of DNA replication in eukaryotes, including the mechanism of initiation and its control. This review focuses on the current understanding of how the origin recognition complex (ORC) contributes to determining the location of replication initiation in the multiple chromosomes within eukaryotic cells, as well as methods for mapping the location and temporal patterning of DNA replication. Origin specification and configuration vary substantially between eukaryotic species and in some cases co-evolved with gene-silencing mechanisms. We discuss the possibility that centromeres and origins of DNA replication were originally derived from a common element and later separated during evolution.
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Affiliation(s)
- Yixin Hu
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA; Program in Molecular and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Bruce Stillman
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
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17
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Choudhary K, Kupiec M. The cohesin complex of yeasts: sister chromatid cohesion and beyond. FEMS Microbiol Rev 2023; 47:6825453. [PMID: 36370456 DOI: 10.1093/femsre/fuac045] [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: 09/13/2022] [Revised: 11/07/2022] [Accepted: 11/09/2022] [Indexed: 11/13/2022] Open
Abstract
Each time a cell divides, it needs to duplicate the genome and then separate the two copies. In eukaryotes, which usually have more than one linear chromosome, this entails tethering the two newly replicated DNA molecules, a phenomenon known as sister chromatid cohesion (SCC). Cohesion ensures proper chromosome segregation to separate poles during mitosis. SCC is achieved by the presence of the cohesin complex. Besides its canonical function, cohesin is essential for chromosome organization and DNA damage repair. Surprisingly, yeast cohesin is loaded in G1 before DNA replication starts but only acquires its binding activity during DNA replication. Work in microorganisms, such as Saccharomyces cerevisiae and Schizosaccharomyces pombe has greatly contributed to the understanding of cohesin composition and functions. In the last few years, much progress has been made in elucidating the role of cohesin in chromosome organization and compaction. Here, we discuss the different functions of cohesin to ensure faithful chromosome segregation and genome stability during the mitotic cell division in yeast. We describe what is known about its composition and how DNA replication is coupled with SCC establishment. We also discuss current models for the role of cohesin in chromatin loop extrusion and delineate unanswered questions about the activity of this important, conserved complex.
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Affiliation(s)
- Karan Choudhary
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Martin Kupiec
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
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18
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Khan SR, Sakib S, Rahman MS, Samee MAH. DeepBend: An interpretable model of DNA bendability. iScience 2023; 26:105945. [PMID: 36866046 PMCID: PMC9971889 DOI: 10.1016/j.isci.2023.105945] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 12/05/2022] [Accepted: 01/05/2023] [Indexed: 01/09/2023] Open
Abstract
The bendability of genomic DNA impacts chromatin packaging and protein-DNA binding. However, we do not have a comprehensive understanding of the motifs influencing DNA bendability. Recent high-throughput technologies such as Loop-Seq offer an opportunity to address this gap but the lack of accurate and interpretable machine learning models still remains. Here we introduce DeepBend, a convolutional neural network model with convolutions designed to directly capture the motifs underlying DNA bendability and their periodic occurrences or relative arrangements that modulate bendability. DeepBend consistently performs on par with alternative models while giving an extra edge through mechanistic interpretations. Besides confirming the known motifs of DNA bendability, DeepBend also revealed several novel motifs and showed how the spatial patterns of motif occurrences influence bendability. DeepBend's genome-wide prediction of bendability further showed how bendability is linked to chromatin conformation and revealed the motifs controlling the bendability of topologically associated domains and their boundaries.
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Affiliation(s)
- Samin Rahman Khan
- Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
| | - Sadman Sakib
- Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
| | - M. Sohel Rahman
- Bangladesh University of Engineering and Technology, Dhaka, Bangladesh,Corresponding author
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19
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Álvarez-González L, Arias-Sardá C, Montes-Espuña L, Marín-Gual L, Vara C, Lister NC, Cuartero Y, Garcia F, Deakin J, Renfree MB, Robinson TJ, Martí-Renom MA, Waters PD, Farré M, Ruiz-Herrera A. Principles of 3D chromosome folding and evolutionary genome reshuffling in mammals. Cell Rep 2022; 41:111839. [PMID: 36543130 DOI: 10.1016/j.celrep.2022.111839] [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: 06/18/2022] [Revised: 10/01/2022] [Accepted: 11/24/2022] [Indexed: 12/24/2022] Open
Abstract
Studying the similarities and differences in genomic interactions between species provides fertile grounds for determining the evolutionary dynamics underpinning genome function and speciation. Here, we describe the principles of 3D genome folding in vertebrates and show how lineage-specific patterns of genome reshuffling can result in different chromatin configurations. We (1) identified different patterns of chromosome folding in across vertebrate species (centromere clustering versus chromosomal territories); (2) reconstructed ancestral marsupial and afrotherian genomes analyzing whole-genome sequences of species representative of the major therian phylogroups; (3) detected lineage-specific chromosome rearrangements; and (4) identified the dynamics of the structural properties of genome reshuffling through therian evolution. We present evidence of chromatin configurational changes that result from ancestral inversions and fusions/fissions. We catalog the close interplay between chromatin higher-order organization and therian genome evolution and introduce an interpretative hypothesis that explains how chromatin folding influences evolutionary patterns of genome reshuffling.
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Affiliation(s)
- Lucía Álvarez-González
- Departament de Biologia Cel·lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain; Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | | | - Laia Montes-Espuña
- Departament de Biologia Cel·lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain; Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | - Laia Marín-Gual
- Departament de Biologia Cel·lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain; Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | - Covadonga Vara
- Departament de Biologia Cel·lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain; Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | - Nicholas C Lister
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Yasmina Cuartero
- CNAG-CRG, Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Baldiri Reixac 4, 08028 Barcelona, Spain
| | - Francisca Garcia
- Servei de Cultius Cel.lulars-SCAC, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | - Janine Deakin
- Institute for Applied Ecology, University of Canberra, Bruce, ACT 2617, Australia
| | - Marilyn B Renfree
- School of Biosciences, The University of Melbourne, Victoria, VIC 3010, Australia
| | - Terence J Robinson
- Evolutionary Genomics Group, Department of Botany and Zoology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa
| | - Marc A Martí-Renom
- CNAG-CRG, Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Baldiri Reixac 4, 08028 Barcelona, Spain; Centre for Genomic Regulation, The Barcelona Institute for Science and Technology, Carrer del Doctor Aiguader 88, 08003 Barcelona, Spain; ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain; Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Paul D Waters
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Marta Farré
- School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Aurora Ruiz-Herrera
- Departament de Biologia Cel·lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain; Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.
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20
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Attou A, Zülske T, Wedemann G. Cohesin and CTCF complexes mediate contacts in chromatin loops depending on nucleosome positions. Biophys J 2022; 121:4788-4799. [PMID: 36325618 PMCID: PMC9811664 DOI: 10.1016/j.bpj.2022.10.044] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 09/12/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022] Open
Abstract
The spatial organization of the eukaryotic genome plays an important role in regulating transcriptional activity. In the nucleus, chromatin forms loops that assemble into fundamental units called topologically associating domains that facilitate or inhibit long-range contacts. These loops are formed and held together by the ring-shaped cohesin protein complex, and this can involve binding of CCCTC-binding factor (CTCF). High-resolution conformation capture experiments provide the frequency at which two DNA fragments physically associate in three-dimensional space. However, technical limitations of this approach, such as low throughput, low resolution, or noise in contact maps, make data interpretation and identification of chromatin intraloop contacts, e.g., between distal regulatory elements and their target genes, challenging. Herein, an existing coarse-grained model of chromatin at single-nucleosome resolution was extended by integrating potentials describing CTCF and cohesin. We performed replica-exchange Monte Carlo simulations with regularly spaced nucleosomes and experimentally determined nucleosome positions in the presence of cohesin-CTCF, as well as depleted systems as controls. In fully extruded loops caused by the presence of cohesin and CTCF, the number of contacts within the formed loops was increased. The number and types of these contacts were impacted by the nucleosome distribution and loop size. Microloops were observed within cohesin-mediated loops due to thermal fluctuations without additional influence of other factors, and the number, size, and shape of microloops were determined by nucleosome distribution and loop size. Nucleosome positions directly affect the spatial structure and contact probability within a loop, with presumed consequences for transcriptional activity.
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Affiliation(s)
- Aymen Attou
- Competence Center Bioinformatics, Institute for Applied Computer Science, Hochschule Stralsund, Stralsund, Germany
| | - Tilo Zülske
- Competence Center Bioinformatics, Institute for Applied Computer Science, Hochschule Stralsund, Stralsund, Germany
| | - Gero Wedemann
- Competence Center Bioinformatics, Institute for Applied Computer Science, Hochschule Stralsund, Stralsund, Germany.
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21
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Kakui Y, Barrington C, Kusano Y, Thadani R, Fallesen T, Hirota T, Uhlmann F. Chromosome arm length, and a species-specific determinant, define chromosome arm width. Cell Rep 2022; 41:111753. [PMID: 36476849 DOI: 10.1016/j.celrep.2022.111753] [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: 04/20/2022] [Revised: 09/05/2022] [Accepted: 11/09/2022] [Indexed: 12/12/2022] Open
Abstract
Mitotic chromosomes in different organisms adopt various dimensions. What defines these dimensions is scarcely understood. Here, we compare mitotic chromosomes in budding and fission yeasts harboring similarly sized genomes distributed among 16 or 3 chromosomes, respectively. Hi-C analyses and superresolution microscopy reveal that budding yeast chromosomes are characterized by shorter-ranging mitotic chromatin contacts and are thinner compared with the thicker fission yeast chromosomes that contain longer-ranging mitotic contacts. These distinctions persist even after budding yeast chromosomes are fused to form three fission-yeast-length entities, revealing a species-specific organizing principle. Species-specific widths correlate with the known binding site intervals of the chromosomal condensin complex. Unexpectedly, within each species, we find that longer chromosome arms are always thicker and harbor longer-ranging contacts, a trend that we also observe with human chromosomes. Arm length as a chromosome width determinant informs mitotic chromosome formation models.
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Affiliation(s)
- Yasutaka Kakui
- Waseda Institute for Advanced Study, Waseda University, Tokyo 169-0051, Japan; Laboratory of Cytoskeletal Logistics, Center for Advanced Biomedical Sciences, Waseda University, Tokyo 162-8480, Japan; Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
| | - Christopher Barrington
- Bioinformatics & Biostatistics Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Yoshiharu Kusano
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan
| | - Rahul Thadani
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Todd Fallesen
- Advanced Light Microscopy Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Toru Hirota
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
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22
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Amankwaa B, Schoborg T, Labrador M. Drosophila insulator proteins exhibit in vivo liquid-liquid phase separation properties. Life Sci Alliance 2022; 5:5/12/e202201536. [PMID: 35853678 PMCID: PMC9297610 DOI: 10.26508/lsa.202201536] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 07/05/2022] [Accepted: 07/06/2022] [Indexed: 11/24/2022] Open
Abstract
Drosophila insulator proteins and the cohesin subunit Rad21 coalesce in vivo to form liquid-droplet condensates, suggesting that liquid–liquid phase separation mediates their function in 3D genome organization. Mounting evidence implicates liquid–liquid phase separation (LLPS), the condensation of biomolecules into liquid-like droplets in the formation and dissolution of membraneless intracellular organelles (MLOs). Cells use MLOs or condensates for various biological processes, including emergency signaling and spatiotemporal control over steady-state biochemical reactions and heterochromatin formation. Insulator proteins are architectural elements involved in establishing independent domains of transcriptional activity within eukaryotic genomes. In Drosophila, insulator proteins form nuclear foci known as insulator bodies in response to osmotic stress. However, the mechanism through which insulator proteins assemble into bodies is yet to be investigated. Here, we identify signatures of LLPS by insulator bodies, including high disorder tendency in insulator proteins, scaffold–client–dependent assembly, extensive fusion behavior, sphericity, and sensitivity to 1,6-hexanediol. We also show that the cohesin subunit Rad21 is a component of insulator bodies, adding to the known insulator protein constituents and γH2Av. Our data suggest a concerted role of cohesin and insulator proteins in insulator body formation and under physiological conditions. We propose a mechanism whereby these architectural proteins modulate 3D genome organization through LLPS.
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Affiliation(s)
- Bright Amankwaa
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, USA
| | - Todd Schoborg
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, USA
| | - Mariano Labrador
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, USA
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23
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Matthey-Doret C, Colp MJ, Escoll P, Thierry A, Moreau P, Curtis B, Sahr T, Sarrasin M, Gray MW, Lang BF, Archibald JM, Buchrieser C, Koszul R. Chromosome-scale assemblies of Acanthamoeba castellanii genomes provide insights into Legionella pneumophila infection-related chromatin reorganization. Genome Res 2022; 32:1698-1710. [PMID: 36109147 PMCID: PMC9528979 DOI: 10.1101/gr.276375.121] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 07/25/2022] [Indexed: 11/24/2022]
Abstract
The unicellular amoeba Acanthamoeba castellanii is ubiquitous in aquatic environments, where it preys on bacteria. The organism also hosts bacterial endosymbionts, some of which are parasitic, including human pathogens such as Chlamydia and Legionella spp. Here we report complete, high-quality genome sequences for two extensively studied A. castellanii strains, Neff and C3. Combining long- and short-read data with Hi-C, we generated near chromosome-level assemblies for both strains with 90% of the genome contained in 29 scaffolds for the Neff strain and 31 for the C3 strain. Comparative genomics revealed strain-specific functional enrichment, most notably genes related to signal transduction in the C3 strain and to viral replication in Neff. Furthermore, we characterized the spatial organization of the A. castellanii genome and showed that it is reorganized during infection by Legionella pneumophila Infection-dependent chromatin loops were found to be enriched in genes for signal transduction and phosphorylation processes. In genomic regions where chromatin organization changed during Legionella infection, we found functional enrichment for genes associated with metabolism, organelle assembly, and cytoskeleton organization. Given Legionella infection is known to alter its host's cell cycle, to exploit the host's organelles, and to modulate the host's metabolism in its favor, these changes in chromatin organization may partly be related to mechanisms of host control during Legionella infection.
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Affiliation(s)
- Cyril Matthey-Doret
- Institut Pasteur, CNRS UMR 3525, Université de Paris, Unité Régulation Spatiale des Génomes, F-75015 Paris, France
- Collège Doctoral, Sorbonne Université, F-75005 Paris, France
| | - Morgan J Colp
- Department of Biochemistry and Molecular Biology and Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Pedro Escoll
- Institut Pasteur, Université de Paris, Biologie des Bactéries Intracellulaires and CNRS UMR 6047, F-75015 Paris, France
| | - Agnès Thierry
- Institut Pasteur, CNRS UMR 3525, Université de Paris, Unité Régulation Spatiale des Génomes, F-75015 Paris, France
| | - Pierrick Moreau
- Institut Pasteur, CNRS UMR 3525, Université de Paris, Unité Régulation Spatiale des Génomes, F-75015 Paris, France
| | - Bruce Curtis
- Department of Biochemistry and Molecular Biology and Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Tobias Sahr
- Institut Pasteur, Université de Paris, Biologie des Bactéries Intracellulaires and CNRS UMR 6047, F-75015 Paris, France
| | - Matt Sarrasin
- Robert Cedergren Centre for Bioinformatics and Genomics, Département de Biochimie, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | - Michael W Gray
- Department of Biochemistry and Molecular Biology and Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - B Franz Lang
- Robert Cedergren Centre for Bioinformatics and Genomics, Département de Biochimie, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | - John M Archibald
- Department of Biochemistry and Molecular Biology and Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Carmen Buchrieser
- Institut Pasteur, Université de Paris, Biologie des Bactéries Intracellulaires and CNRS UMR 6047, F-75015 Paris, France
| | - Romain Koszul
- Institut Pasteur, CNRS UMR 3525, Université de Paris, Unité Régulation Spatiale des Génomes, F-75015 Paris, France
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24
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Choudhary K, Itzkovich Z, Alonso-Perez E, Bishara H, Dunn B, Sherlock G, Kupiec M. S. cerevisiae Cells Can Grow without the Pds5 Cohesin Subunit. mBio 2022; 13:e0142022. [PMID: 35708277 PMCID: PMC9426526 DOI: 10.1128/mbio.01420-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 05/31/2022] [Indexed: 12/11/2022] Open
Abstract
During DNA replication, the newly created sister chromatids are held together until their separation at anaphase. The cohesin complex is in charge of creating and maintaining sister chromatid cohesion (SCC) in all eukaryotes. In Saccharomyces cerevisiae cells, cohesin is composed of two elongated proteins, Smc1 and Smc3, bridged by the kleisin Mcd1/Scc1. The latter also acts as a scaffold for three additional proteins, Scc3/Irr1, Wpl1/Rad61, and Pds5. Although the HEAT-repeat protein Pds5 is essential for cohesion, its precise function is still debated. Deletion of the ELG1 gene, encoding a PCNA unloader, can partially suppress the temperature-sensitive pds5-1 allele, but not a complete deletion of PDS5. We carried out a genetic screen for high-copy-number suppressors and another for spontaneously arising mutants, allowing the survival of a pds5Δ elg1Δ strain. Our results show that cells remain viable in the absence of Pds5 provided that there is both an elevation in the level of Mcd1 (which can be due to mutations in the CLN2 gene, encoding a G1 cyclin), and an increase in the level of SUMO-modified PCNA on chromatin (caused by lack of PCNA unloading in elg1Δ mutants). The elevated SUMO-PCNA levels increase the recruitment of the Srs2 helicase, which evicts Rad51 molecules from the moving fork, creating single-stranded DNA (ssDNA) regions that serve as sites for increased cohesin loading and SCC establishment. Thus, our results delineate a double role for Pds5 in protecting the cohesin ring and interacting with the DNA replication machinery. IMPORTANCE Sister chromatid cohesion is vital for faithful chromosome segregation, chromosome folding into loops, and gene expression. A multisubunit protein complex known as cohesin holds the sister chromatids from S phase until the anaphase stage. In this study, we explore the function of the essential cohesin subunit Pds5 in the regulation of sister chromatid cohesion. We performed two independent genetic screens to bypass the function of the Pds5 protein. We observe that Pds5 protein is a cohesin stabilizer, and elevating the levels of Mcd1 protein along with SUMO-PCNA accumulation on chromatin can compensate for the loss of the PDS5 gene. In addition, Pds5 plays a role in coordinating the DNA replication and sister chromatid cohesion establishment. This work elucidates the function of cohesin subunit Pds5, the G1 cyclin Cln2, and replication factors PCNA, Elg1, and Srs2 in the proper regulation of sister chromatid cohesion.
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Affiliation(s)
- Karan Choudhary
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv, Israel
| | - Ziv Itzkovich
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv, Israel
| | - Elisa Alonso-Perez
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv, Israel
| | - Hend Bishara
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv, Israel
| | - Barbara Dunn
- Departments of Genetics, Stanford University, Stanford, California, USA
| | - Gavin Sherlock
- Departments of Genetics, Stanford University, Stanford, California, USA
| | - Martin Kupiec
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv, Israel
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25
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Jeppsson K, Sakata T, Nakato R, Milanova S, Shirahige K, Björkegren C. Cohesin-dependent chromosome loop extrusion is limited by transcription and stalled replication forks. SCIENCE ADVANCES 2022; 8:eabn7063. [PMID: 35687682 PMCID: PMC9187231 DOI: 10.1126/sciadv.abn7063] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 12/15/2021] [Accepted: 04/27/2022] [Indexed: 05/31/2023]
Abstract
Genome function depends on regulated chromosome folding, and loop extrusion by the protein complex cohesin is essential for this multilayered organization. The chromosomal positioning of cohesin is controlled by transcription, and the complex also localizes to stalled replication forks. However, the role of transcription and replication in chromosome looping remains unclear. Here, we show that reduction of chromosome-bound RNA polymerase weakens normal cohesin loop extrusion boundaries, allowing cohesin to form new long-range chromosome cis interactions. Stress response genes induced by transcription inhibition are also shown to act as new loop extrusion boundaries. Furthermore, cohesin loop extrusion during early S phase is jointly controlled by transcription and replication units. Together, the results reveal that replication and transcription machineries are chromosome-folding regulators that block the progression of loop-extruding cohesin, opening for new perspectives on cohesin's roles in genome function and stability.
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Affiliation(s)
- Kristian Jeppsson
- Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden
- Institute for Quantitative Bioscience, Tokyo University, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Toyonori Sakata
- Institute for Quantitative Bioscience, Tokyo University, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Ryuichiro Nakato
- Institute for Quantitative Bioscience, Tokyo University, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Stefina Milanova
- Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden
| | - Katsuhiko Shirahige
- Institute for Quantitative Bioscience, Tokyo University, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Camilla Björkegren
- Karolinska Institutet, Department of Biosciences and Nutrition, Neo, Hälsovägen 7c, 141 83 Huddinge, Sweden
- Karolinska Institutet, Department of Cell and Molecular Biology, Biomedicum, Tomtebodavägen 16, 171 77 Stockholm, Sweden
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26
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Bastié N, Chapard C, Dauban L, Gadal O, Beckouët F, Koszul R. Smc3 acetylation, Pds5 and Scc2 control the translocase activity that establishes cohesin-dependent chromatin loops. Nat Struct Mol Biol 2022; 29:575-585. [PMID: 35710835 DOI: 10.1038/s41594-022-00780-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 04/04/2022] [Indexed: 02/07/2023]
Abstract
Cohesin is a DNA translocase that is instrumental in the folding of the genome into chromatin loops, with functional consequences on DNA-related processes. Chromatin loop length and organization likely depend on cohesin processivity, translocation rate and stability on DNA. Here, we investigate and provide a comprehensive overview of the roles of various cohesin regulators in tuning chromatin loop expansion in budding yeast Saccharomyces cerevisiae. We demonstrate that Scc2, which stimulates cohesin ATPase activity, is also essential for cohesin translocation, driving loop expansion in vivo. Smc3 acetylation during the S phase counteracts this activity through the stabilization of Pds5, which finely tunes the size and stability of loops in G2.
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Affiliation(s)
- Nathalie Bastié
- Molecular, Cellular and Developmental biology department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Christophe Chapard
- Institut Pasteur, CNRS UMR3525, Université Paris Cité, Unité Régulation Spatiale des Génomes, Paris, France
| | - Lise Dauban
- Molecular, Cellular and Developmental biology department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
- Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Olivier Gadal
- Molecular, Cellular and Developmental biology department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Frédéric Beckouët
- Molecular, Cellular and Developmental biology department (MCD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.
| | - Romain Koszul
- Institut Pasteur, CNRS UMR3525, Université Paris Cité, Unité Régulation Spatiale des Génomes, Paris, France.
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27
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van Ruiten MS, van Gent D, Sedeño Cacciatore Á, Fauster A, Willems L, Hekkelman ML, Hoekman L, Altelaar M, Haarhuis JHI, Brummelkamp TR, de Wit E, Rowland BD. The cohesin acetylation cycle controls chromatin loop length through a PDS5A brake mechanism. Nat Struct Mol Biol 2022; 29:586-591. [PMID: 35710836 PMCID: PMC9205776 DOI: 10.1038/s41594-022-00773-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 04/05/2022] [Indexed: 12/16/2022]
Abstract
Cohesin structures the genome through the formation of chromatin loops and by holding together the sister chromatids. The acetylation of cohesin's SMC3 subunit is a dynamic process that involves the acetyltransferase ESCO1 and deacetylase HDAC8. Here we show that this cohesin acetylation cycle controls the three-dimensional genome in human cells. ESCO1 restricts the length of chromatin loops, and of architectural stripes emanating from CTCF sites. HDAC8 conversely promotes the extension of such loops and stripes. This role in controlling loop length turns out to be distinct from the canonical role of cohesin acetylation that protects against WAPL-mediated DNA release. We reveal that acetylation controls the interaction of cohesin with PDS5A to restrict chromatin loop length. Our data support a model in which this PDS5A-bound state acts as a brake that enables the pausing and restart of loop enlargement. The cohesin acetylation cycle hereby provides punctuation in the process of genome folding.
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Affiliation(s)
- Marjon S van Ruiten
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Démi van Gent
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | | | - Astrid Fauster
- Division of Biochemistry, Oncode Institute, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Laureen Willems
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Maarten L Hekkelman
- Division of Biochemistry, Oncode Institute, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Liesbeth Hoekman
- Proteomics Facility, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Maarten Altelaar
- Proteomics Facility, The Netherlands Cancer Institute, Amsterdam, the Netherlands
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, Utrecht Institute for Pharmaceutical Sciences, Utrecht University and Netherlands Proteomics Centre, Utrecht, the Netherlands
| | - Judith H I Haarhuis
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Thijn R Brummelkamp
- Division of Biochemistry, Oncode Institute, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Elzo de Wit
- Division of Gene Regulation, Oncode Institute, 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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28
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Barton RE, Massari LF, Robertson D, Marston AL. Eco1-dependent cohesin acetylation anchors chromatin loops and cohesion to define functional meiotic chromosome domains. eLife 2022; 11:e74447. [PMID: 35103590 PMCID: PMC8856730 DOI: 10.7554/elife.74447] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 01/28/2022] [Indexed: 11/13/2022] Open
Abstract
Cohesin organizes the genome by forming intra-chromosomal loops and inter-sister chromatid linkages. During gamete formation by meiosis, chromosomes are reshaped to support crossover recombination and two consecutive rounds of chromosome segregation. Here we show that meiotic chromosomes are organised into functional domains by Eco1 acetyltransferase-dependent positioning of both chromatin loops and sister chromatid cohesion in budding yeast. Eco1 acetylates the Smc3 cohesin subunit in meiotic S phase to establish chromatin boundaries, independently of DNA replication. Boundary formation by Eco1 is critical for prophase exit and for the maintenance of cohesion until meiosis II, but is independent of the ability of Eco1 to antagonize the cohesin-release factor, Wpl1. Conversely, prevention of cohesin release by Wpl1 is essential for centromeric cohesion, kinetochore monoorientation and co-segregation of sister chromatids in meiosis I. Our findings establish Eco1 as a key determinant of chromatin boundaries and cohesion positioning, revealing how local chromosome structuring directs genome transmission into gametes.
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Affiliation(s)
- Rachael E Barton
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born CrescentEdinburghUnited Kingdom
| | - Lucia F Massari
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born CrescentEdinburghUnited Kingdom
| | - Daniel Robertson
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born CrescentEdinburghUnited Kingdom
| | - Adèle L Marston
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, Michael Swann Building, Max Born CrescentEdinburghUnited Kingdom
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29
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Higashi TL, Uhlmann F. SMC complexes: Lifting the lid on loop extrusion. Curr Opin Cell Biol 2022; 74:13-22. [PMID: 35016058 PMCID: PMC9089308 DOI: 10.1016/j.ceb.2021.12.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 12/07/2021] [Accepted: 12/08/2021] [Indexed: 01/02/2023]
Abstract
Loop extrusion has emerged as a prominent hypothesis for how SMC complexes shape chromosomes - single molecule in vitro observations have yielded fascinating images of this process. When not extruding loops, SMC complexes are known to topologically entrap one or more DNAs. Here, we review how structural insight into the SMC complex cohesin has led to a molecular framework for both activities: a Brownian ratchet motion, associated with topological DNA entry, might repeat itself to elicit loop extrusion. After contrasting alternative loop extrusion models, we explore whether topological loading or loop extrusion is more adept at explaining in vivo SMC complex function. SMC variants that experimentally separate topological loading from loop extrusion will in the future probe their respective contributions to chromosome biology.
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Affiliation(s)
- Torahiko L Higashi
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, NW1 1AT, UK; Department of Cellular Biochemistry, Kyushu University, Fukuoka, 812-8582, Japan
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, NW1 1AT, UK.
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30
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Phipps J, Dubrana K. DNA Repair in Space and Time: Safeguarding the Genome with the Cohesin Complex. Genes (Basel) 2022; 13:198. [PMID: 35205243 PMCID: PMC8872453 DOI: 10.3390/genes13020198] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 01/20/2022] [Accepted: 01/20/2022] [Indexed: 12/04/2022] Open
Abstract
DNA double-strand breaks (DSBs) are a deleterious form of DNA damage, which must be robustly addressed to ensure genome stability. Defective repair can result in chromosome loss, point mutations, loss of heterozygosity or chromosomal rearrangements, which could lead to oncogenesis or cell death. We explore the requirements for the successful repair of DNA DSBs by non-homologous end joining and homology-directed repair (HDR) mechanisms in relation to genome folding and dynamics. On the occurrence of a DSB, local and global chromatin composition and dynamics, as well as 3D genome organization and break localization within the nuclear space, influence how repair proceeds. The cohesin complex is increasingly implicated as a key regulator of the genome, influencing chromatin composition and dynamics, and crucially genome organization through folding chromosomes by an active loop extrusion mechanism, and maintaining sister chromatid cohesion. Here, we consider how this complex is now emerging as a key player in the DNA damage response, influencing repair pathway choice and efficiency.
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Affiliation(s)
| | - Karine Dubrana
- UMR Stabilité Génétique Cellules Souches et Radiations, INSERM, iRCM/IBFJ CEA, Université de Paris and Université Paris-Saclay, F-92265 Fontenay-aux-Roses, France;
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31
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Sakuno T, Hiraoka Y. Rec8 Cohesin: A Structural Platform for Shaping the Meiotic Chromosomes. Genes (Basel) 2022; 13:200. [PMID: 35205245 PMCID: PMC8871791 DOI: 10.3390/genes13020200] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/17/2022] [Accepted: 01/21/2022] [Indexed: 11/17/2022] Open
Abstract
Meiosis is critically different from mitosis in that during meiosis, pairing and segregation of homologous chromosomes occur. During meiosis, the morphology of sister chromatids changes drastically, forming a prominent axial structure in the synaptonemal complex. The meiosis-specific cohesin complex plays a central role in the regulation of the processes required for recombination. In particular, the Rec8 subunit of the meiotic cohesin complex, which is conserved in a wide range of eukaryotes, has been analyzed for its function in modulating chromosomal architecture during the pairing and recombination of homologous chromosomes in meiosis. Here, we review the current understanding of Rec8 cohesin as a structural platform for meiotic chromosomes.
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Affiliation(s)
| | - Yasushi Hiraoka
- Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan;
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32
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Abstract
3D genome mapping aims at connecting the physics of chromatin folding to the underlying biological events, and applications of various chromosomal conformation capture (3C) assays continue to discover critical roles of genome folding in regulating nuclear functions. To interrogate the full spectrum of chromatin folding ranging from the level of nucleosomes to full chromosomes in mammals, we developed an enhanced 3C-based method called Micro-C. The protocol employs Micrococcal nuclease (MNase) to fragment the genome, which overcomes the resolution limit of restriction enzyme-based methods, enabling the estimation of contact frequencies between proximal nucleosomes. Such improvements successfully resolve the fine-scale level of chromatin folding, including enhancer-promoter or promoter-promoter interactions, genic and nucleosomal folding, and boost the signal-to-noise ratio in detecting loops and substructures underlying TADs. In this chapter, we will thoroughly discuss the details of the Micro-C protocol and critical parameters to consider for generating high-quality Micro-C maps.
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Affiliation(s)
- Elena Slobodyanyuk
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- Li Ka Shing Center for Biomedical and Health Sciences, University of California, Berkeley, Berkeley, CA, USA
- CIRM Center of Excellence, University of California, Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Claudia Cattoglio
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- Li Ka Shing Center for Biomedical and Health Sciences, University of California, Berkeley, Berkeley, CA, USA
- CIRM Center of Excellence, University of California, Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Tsung-Han S Hsieh
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
- Li Ka Shing Center for Biomedical and Health Sciences, University of California, Berkeley, Berkeley, CA, USA.
- CIRM Center of Excellence, University of California, Berkeley, Berkeley, CA, USA.
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA.
- Center for Computational Biology, University of California, Berkeley, Berkeley, CA, USA.
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33
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3D Genome Organization: Causes and Consequences for DNA Damage and Repair. Genes (Basel) 2021; 13:genes13010007. [PMID: 35052348 PMCID: PMC8775012 DOI: 10.3390/genes13010007] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 12/16/2021] [Accepted: 12/18/2021] [Indexed: 01/02/2023] Open
Abstract
The inability to repair damaged DNA severely compromises the integrity of any organism. In eukaryotes, the DNA damage response (DDR) operates within chromatin, a tightly organized DNA–histone complex in a non-random manner within the nucleus. Chromatin thus orchestrates various cellular processes, including repair. Here, we examine the chromatin landscape before, during, and after the DNA damage, focusing on double strand breaks (DSBs). We study how chromatin is modified during the repair process, not only around the damaged region (in cis), but also genome-wide (in trans). Recent evidence has highlighted a complex landscape in which different chromatin parameters (stiffness, compaction, loops) are transiently modified, defining “codes” for each specific stage of the DDR. We illustrate a novel aspect of DDR where chromatin modifications contribute to the movement of DSB-damaged chromatin, as well as undamaged chromatin, ensuring the mobilization of DSBs, their clustering, and their repair processes.
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34
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Jo H, Kim T, Chun Y, Jung I, Lee D. A compendium of chromatin contact maps reflecting regulation by chromatin remodelers in budding yeast. Nat Commun 2021; 12:6380. [PMID: 34737268 PMCID: PMC8569116 DOI: 10.1038/s41467-021-26629-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 10/14/2021] [Indexed: 11/09/2022] Open
Abstract
We herein employ in situ Hi-C with an auxin-inducible degron (AID) system to examine the effect of chromatin remodeling on 3D genome organization in yeast. Eight selected ATP-dependent chromatin remodelers representing various subfamilies contribute to 3D genome organization differently. Among the studied remodelers, the temporary depletions of Chd1p, Swr1p, and Sth1p (a catalytic subunit of the Remodeling the Structure of Chromatin [RSC] complex) cause the most significant defects in intra-chromosomal contacts, and the regulatory roles of these three remodelers in 3D genome organization differ depending on the chromosomal context and cell cycle stage. Furthermore, even though Chd1p and Isw1p are known to share functional similarities/redundancies, their depletions lead to distinct effects on 3D structures. The RSC and cohesin complexes also differentially modulate 3D genome organization within chromosome arm regions, whereas RSC appears to support the function of cohesin in centromeric clustering at G2 phase. Our work suggests that the ATP-dependent chromatin remodelers control the 3D genome organization of yeast through their chromatin-remodeling activities.
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Affiliation(s)
- Hyelim Jo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Taemook Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Yujin Chun
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Inkyung Jung
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Daeyoup Lee
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea.
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35
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Piazza A, Bordelet H, Dumont A, Thierry A, Savocco J, Girard F, Koszul R. Cohesin regulates homology search during recombinational DNA repair. Nat Cell Biol 2021; 23:1176-1186. [PMID: 34750581 DOI: 10.1038/s41556-021-00783-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 09/27/2021] [Indexed: 02/06/2023]
Abstract
Homologous recombination repairs DNA double-strand breaks (DSB) using an intact dsDNA molecule as a template. It entails a homology search step, carried out along a conserved RecA/Rad51-ssDNA filament assembled on each DSB end. Whether, how and to what extent a DSB impacts chromatin folding, and how this (re)organization in turns influences the homology search process, remain ill-defined. Here we characterize two layers of spatial chromatin reorganization following DSB formation in Saccharomyces cerevisiae. Although cohesin folds chromosomes into cohesive arrays of ~20-kb-long chromatin loops as cells arrest in G2/M, the DSB-flanking regions interact locally in a resection- and 9-1-1 clamp-dependent manner, independently of cohesin, Mec1ATR, Rad52 and Rad51. This local structure blocks cohesin progression, constraining the DSB region at the base of a loop. Functionally, cohesin promotes DSB-dsDNA interactions and donor identification in cis, while inhibiting them in trans. This study identifies multiple direct and indirect ways by which cohesin regulates homology search during recombinational DNA repair.
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Affiliation(s)
- Aurèle Piazza
- Institut Pasteur, CNRS UMR3525, Unité Régulation Spatiale des Génomes, F-75015, Paris, France.
- Université de Lyon, ENS de Lyon, Université Claude Bernard, Laboratoire de Biologie et Modélisation de la Cellule, CNRS UMR5239, INSERM U1210, 46 allée d'Italie, 69007, Lyon, France.
| | - Hélène Bordelet
- Institut Pasteur, CNRS UMR3525, Unité Régulation Spatiale des Génomes, F-75015, Paris, France
- Université de Lyon, ENS de Lyon, Université Claude Bernard, Laboratoire de Biologie et Modélisation de la Cellule, CNRS UMR5239, INSERM U1210, 46 allée d'Italie, 69007, Lyon, France
| | - Agnès Dumont
- Université de Lyon, ENS de Lyon, Université Claude Bernard, Laboratoire de Biologie et Modélisation de la Cellule, CNRS UMR5239, INSERM U1210, 46 allée d'Italie, 69007, Lyon, France
| | - Agnès Thierry
- Institut Pasteur, CNRS UMR3525, Unité Régulation Spatiale des Génomes, F-75015, Paris, France
| | - Jérôme Savocco
- Université de Lyon, ENS de Lyon, Université Claude Bernard, Laboratoire de Biologie et Modélisation de la Cellule, CNRS UMR5239, INSERM U1210, 46 allée d'Italie, 69007, Lyon, France
| | - Fabien Girard
- Institut Pasteur, CNRS UMR3525, Unité Régulation Spatiale des Génomes, F-75015, Paris, France
| | - Romain Koszul
- Institut Pasteur, CNRS UMR3525, Unité Régulation Spatiale des Génomes, F-75015, Paris, France.
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36
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Golov AK, Golova AV, Gavrilov AA, Razin SV. Sensitivity of cohesin-chromatin association to high-salt treatment corroborates non-topological mode of loop extrusion. Epigenetics Chromatin 2021; 14:36. [PMID: 34321070 PMCID: PMC8320178 DOI: 10.1186/s13072-021-00411-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 07/19/2021] [Indexed: 12/18/2022] Open
Abstract
Cohesin is a key organizer of chromatin folding in eukaryotic cells. The two main activities of this ring-shaped protein complex are the maintenance of sister chromatid cohesion and the establishment of long-range DNA-DNA interactions through the process of loop extrusion. Although the basic principles of both cohesion and loop extrusion have been described, we still do not understand several crucial mechanistic details. One of such unresolved issues is the question of whether a cohesin ring topologically embraces DNA string(s) during loop extrusion. Here, we show that cohesin complexes residing on CTCF-occupied genomic sites in mammalian cells do not interact with DNA topologically. We assessed the stability of cohesin-dependent loops and cohesin association with chromatin in high-ionic-strength conditions in G1-synchronized HeLa cells. We found that increased salt concentration completely displaces cohesin from those genomic regions that correspond to CTCF-defined loop anchors. Unsurprisingly, CTCF-anchored cohesin loops also dissipate in these conditions. Because topologically engaged cohesin is considered to be salt resistant, our data corroborate a non-topological model of loop extrusion. We also propose a model of cohesin activity throughout the interphase, which essentially equates the termination of non-topological loop extrusion with topological loading of cohesin. This theoretical framework enables a parsimonious explanation of various seemingly contradictory experimental findings.
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Affiliation(s)
- Arkadiy K. Golov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- Mental Health Research Center, Moscow, Russia
| | - Anastasia V. Golova
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Alexey A. Gavrilov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - Sergey V. Razin
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
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Davidson IF, Peters JM. Genome folding through loop extrusion by SMC complexes. Nat Rev Mol Cell Biol 2021; 22:445-464. [PMID: 33767413 DOI: 10.1038/s41580-021-00349-7] [Citation(s) in RCA: 218] [Impact Index Per Article: 72.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/03/2021] [Indexed: 02/02/2023]
Abstract
Genomic DNA is folded into loops and topologically associating domains (TADs), which serve important structural and regulatory roles. It has been proposed that these genomic structures are formed by a loop extrusion process, which is mediated by structural maintenance of chromosomes (SMC) protein complexes. Recent single-molecule studies have shown that the SMC complexes condensin and cohesin are indeed able to extrude DNA into loops. In this Review, we discuss how the loop extrusion hypothesis can explain key features of genome architecture; cellular functions of loop extrusion, such as separation of replicated DNA molecules, facilitation of enhancer-promoter interactions and immunoglobulin gene recombination; and what is known about the mechanism of loop extrusion and its regulation, for example, by chromatin boundaries that depend on the DNA binding protein CTCF. We also discuss how the loop extrusion hypothesis has led to a paradigm shift in our understanding of both genome architecture and the functions of SMC complexes.
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Affiliation(s)
- Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria.
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38
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Antony J, Chin CV, Horsfield JA. Cohesin Mutations in Cancer: Emerging Therapeutic Targets. Int J Mol Sci 2021; 22:6788. [PMID: 34202641 PMCID: PMC8269296 DOI: 10.3390/ijms22136788] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/08/2021] [Accepted: 06/18/2021] [Indexed: 12/12/2022] Open
Abstract
The cohesin complex is crucial for mediating sister chromatid cohesion and for hierarchal three-dimensional organization of the genome. Mutations in cohesin genes are present in a range of cancers. Extensive research over the last few years has shown that cohesin mutations are key events that contribute to neoplastic transformation. Cohesin is involved in a range of cellular processes; therefore, the impact of cohesin mutations in cancer is complex and can be cell context dependent. Candidate targets with therapeutic potential in cohesin mutant cells are emerging from functional studies. Here, we review emerging targets and pharmacological agents that have therapeutic potential in cohesin mutant cells.
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Affiliation(s)
- Jisha Antony
- Department of Pathology, Otago Medical School, University of Otago, Dunedin 9016, New Zealand;
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland 1010, New Zealand
| | - Chue Vin Chin
- Department of Pathology, Otago Medical School, University of Otago, Dunedin 9016, New Zealand;
| | - Julia A. Horsfield
- Department of Pathology, Otago Medical School, University of Otago, Dunedin 9016, New Zealand;
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland 1010, New Zealand
- Genetics Otago Research Centre, University of Otago, Dunedin 9016, New Zealand
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39
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Abstract
Cohesin helps mediate sister chromatid cohesion, chromosome condensation, DNA repair, and transcription regulation. We exploited proximity-dependent labeling to define the in vivo interactions of cohesin domains with DNA or with other cohesin domains that lie within the same or in different cohesin complexes. Our results suggest that both cohesin's head and hinge domains are proximal to DNA, and cohesin structure is dynamic with differential folding of its coiled coil regions to generate butterfly confirmations. This method also reveals that cohesins form ordered clusters on and off DNA. The levels of cohesin clusters and their distribution on chromosomes are cell cycle-regulated. Cohesin clustering is likely necessary for cohesion maintenance because clustering and maintenance uniquely require the same subset of cohesin domains and the auxiliary cohesin factor Pds5p. These conclusions provide important new mechanistic and biological insights into the architecture of the cohesin complex, cohesin-cohesin interactions, and cohesin's tethering and loop-extruding activities.
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Affiliation(s)
- Siheng Xiang
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
| | - Douglas Koshland
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
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Bonnet A, Lesage P. Light and shadow on the mechanisms of integration site selection in yeast Ty retrotransposon families. Curr Genet 2021; 67:347-357. [PMID: 33590295 DOI: 10.1007/s00294-021-01154-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/04/2021] [Accepted: 01/07/2021] [Indexed: 12/21/2022]
Abstract
Transposable elements are ubiquitous in genomes. Their successful expansion depends in part on their sites of integration in their host genome. In Saccharomyces cerevisiae, evolution has selected various strategies to target the five Ty LTR-retrotransposon families into gene-poor regions in a genome, where coding sequences occupy 70% of the DNA. The integration of Ty1/Ty2/Ty4 and Ty3 occurs upstream and at the transcription start site of the genes transcribed by RNA polymerase III, respectively. Ty5 has completely different integration site preferences, targeting heterochromatin regions. Here, we review the history that led to the identification of the cellular tethering factors that play a major role in anchoring Ty retrotransposons to their preferred sites. We also question the involvement of additional factors in the fine-tuning of the integration site selection, with several studies converging towards an importance of the structure and organization of the chromatin.
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Affiliation(s)
- Amandine Bonnet
- INSERM U944, CNRS UMR 7212, Genomes and Cell Biology of Disease Unit, Institut de Recherche Saint-Louis, Université de Paris, Hôpital Saint-Louis, Paris, France
| | - Pascale Lesage
- INSERM U944, CNRS UMR 7212, Genomes and Cell Biology of Disease Unit, Institut de Recherche Saint-Louis, Université de Paris, Hôpital Saint-Louis, Paris, France.
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Order and stochasticity in the folding of individual Drosophila genomes. Nat Commun 2021; 12:41. [PMID: 33397980 PMCID: PMC7782554 DOI: 10.1038/s41467-020-20292-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 11/23/2020] [Indexed: 02/06/2023] Open
Abstract
Mammalian and Drosophila genomes are partitioned into topologically associating domains (TADs). Although this partitioning has been reported to be functionally relevant, it is unclear whether TADs represent true physical units located at the same genomic positions in each cell nucleus or emerge as an average of numerous alternative chromatin folding patterns in a cell population. Here, we use a single-nucleus Hi-C technique to construct high-resolution Hi-C maps in individual Drosophila genomes. These maps demonstrate chromatin compartmentalization at the megabase scale and partitioning of the genome into non-hierarchical TADs at the scale of 100 kb, which closely resembles the TAD profile in the bulk in situ Hi-C data. Over 40% of TAD boundaries are conserved between individual nuclei and possess a high level of active epigenetic marks. Polymer simulations demonstrate that chromatin folding is best described by the random walk model within TADs and is most suitably approximated by a crumpled globule build of Gaussian blobs at longer distances. We observe prominent cell-to-cell variability in the long-range contacts between either active genome loci or between Polycomb-bound regions, suggesting an important contribution of stochastic processes to the formation of the Drosophila 3D genome. Genomes are partitioned into topologically associating domains (TADs). Here the authors present single-nucleus Hi-C maps in Drosophila at 10 kb resolution, demonstrating the presence of chromatin compartments in individual nuclei, and partitioning of the genome into non-hierarchical TADs at the scale of 100 kb, which resembles population TAD profiles.
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