1
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Belan S, Parfenyev V. Footprints of loop extrusion in statistics of intra-chromosomal distances: An analytically solvable model. J Chem Phys 2024; 160:124901. [PMID: 38516975 DOI: 10.1063/5.0199573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 03/06/2024] [Indexed: 03/23/2024] Open
Abstract
Active loop extrusion-the process of formation of dynamically growing chromatin loops due to the motor activity of DNA-binding protein complexes-is a firmly established mechanism responsible for chromatin spatial organization at different stages of a cell cycle in eukaryotes and bacteria. The theoretical insight into the effect of loop extrusion on the experimentally measured statistics of chromatin conformation can be gained with an appropriately chosen polymer model. Here, we consider the simplest analytically solvable model of an interphase chromosome, which is treated as an ideal chain with disorder of sufficiently sparse random loops whose conformations are sampled from the equilibrium ensemble. This framework allows us to arrive at the closed-form analytical expression for the mean-squared distance between pairs of genomic loci, which is valid beyond the one-loop approximation in diagrammatic representation. In addition, we analyze the loop-induced deviation of chain conformations from the Gaussian statistics by calculating kurtosis of probability density of the pairwise separation vector. The presented results suggest the possible ways of estimating the characteristics of the loop extrusion process based on the experimental data on the scale-dependent statistics of intra-chromosomal pair-wise distances.
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Affiliation(s)
- Sergey Belan
- Landau Institute for Theoretical Physics, Russian Academy of Sciences, 1-A Akademika Semenova Av., 142432 Chernogolovka, Russia
- National Research University Higher School of Economics, Faculty of Physics, Myasnitskaya 20, 101000 Moscow, Russia
| | - Vladimir Parfenyev
- Landau Institute for Theoretical Physics, Russian Academy of Sciences, 1-A Akademika Semenova Av., 142432 Chernogolovka, Russia
- National Research University Higher School of Economics, Faculty of Physics, Myasnitskaya 20, 101000 Moscow, Russia
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2
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Nozaki T, Weiner B, Kleckner N. Rapid Homolog Juxtaposition During Meiotic Chromosome Pairing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.23.586418. [PMID: 38586034 PMCID: PMC10996542 DOI: 10.1101/2024.03.23.586418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
A central basic feature of meiosis is pairing of homologous maternal and paternal chromosomes ("homologs") intimately along their lengths. Recognition between homologs and their juxtaposition in space are mediated by axis-associated DNA recombination complexes. Additional effects ensure that pairing occurs without ultimately giving entanglements among unrelated chromosomes. Here we examine the process of homolog juxtaposition in real time by 4D fluorescence imaging of tagged chromosomal loci at high spatio-temporal resolution in budding yeast. We discover that corresponding loci start coming together from a quite large distance (∼1.8 µm) and progress to completion of pairing in a very short time, usually less than six minutes (thus, "rapid homolog juxtaposition" or "RHJ"). Juxtaposition initiates by motion-mediated extension of a nascent interhomolog DNA linkage, raising the possibility of a tension-mediated trigger. In a first transition, homolog loci move rapidly together (in ∼30 sec, at speeds of up to ∼60 nm/sec) into a discrete intermediate state corresponding to canonical ∼400 nm axis distance coalignment. Then, after a short pause, crossover/noncrossover differentiation (crossover interference) mediates a second short, rapid transition that brings homologs even closer together. If synaptonemal complex (SC) component Zip1 is present, this transition concomitantly gives final close pairing by axis juxtaposition at ∼100 nm, the "SC distance". We also find that: (i) RHJ occurs after chromosomes acquire their prophase chromosome organization; (ii) is nearly synchronously over thirds (or more) of chromosome lengths; but (iii) is asynchronous throughout the genome. Furthermore, cytoskeleton-mediated movement is important for the timing and distance of RHJ onset and also for ensuring normal progression. Potential implications for local and global aspects of pairing are discussed.
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3
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Lebreton J, Colin L, Chatre E, Bernard P. RNAP II antagonizes mitotic chromatin folding and chromosome segregation by condensin. Cell Rep 2024; 43:113901. [PMID: 38446663 DOI: 10.1016/j.celrep.2024.113901] [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: 08/27/2023] [Revised: 12/07/2023] [Accepted: 02/16/2024] [Indexed: 03/08/2024] Open
Abstract
Condensin shapes mitotic chromosomes by folding chromatin into loops, but whether it does so by DNA-loop extrusion remains speculative. Although loop-extruding cohesin is stalled by transcription, the impact of transcription on condensin, which is enriched at highly expressed genes in many species, remains unclear. Using degrons of Rpb1 or the torpedo nuclease Dhp1XRN2 to either deplete or displace RNAPII on chromatin in fission yeast metaphase cells, we show that RNAPII does not load condensin on DNA. Instead, RNAPII retains condensin in cis and hinders its ability to fold mitotic chromatin and to support chromosome segregation, consistent with the stalling of a loop extruder. Transcription termination by Dhp1 limits such a hindrance. Our results shed light on the integrated functioning of condensin, and we argue that a tight control of transcription underlies mitotic chromosome assembly by loop-extruding condensin.
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Affiliation(s)
- Jérémy Lebreton
- ENS de Lyon, University Lyon, 46 allée d'Italie, 69007 Lyon, France
| | - Léonard Colin
- CNRS Laboratory of Biology and Modelling of the Cell, UMR 5239, ENS de Lyon, 46 allée d'Italie, 69007 Lyon, France
| | - Elodie Chatre
- Lymic-Platim, University Lyon, Université Claude Bernard Lyon 1, ENS de Lyon, CNRS UAR3444, Inserm US8, SFR Biosciences, 50 Avenue Tony Garnier, 69007 Lyon, France
| | - Pascal Bernard
- ENS de Lyon, University Lyon, 46 allée d'Italie, 69007 Lyon, France; CNRS Laboratory of Biology and Modelling of the Cell, UMR 5239, ENS de Lyon, 46 allée d'Italie, 69007 Lyon, France.
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4
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Forte G, Boteva L, Conforto F, Gilbert N, Cook PR, Marenduzzo D. Bridging condensins mediate compaction of mitotic chromosomes. J Cell Biol 2024; 223:e202209113. [PMID: 37976091 PMCID: PMC10655892 DOI: 10.1083/jcb.202209113] [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: 09/28/2022] [Revised: 07/08/2023] [Accepted: 11/01/2023] [Indexed: 11/19/2023] Open
Abstract
Eukaryotic chromosomes compact during mitosis into elongated cylinders-and not the spherical globules expected of self-attracting long flexible polymers. This process is mainly driven by condensin-like proteins. Here, we present Brownian-dynamic simulations involving two types of such proteins with different activities. One, which we refer to as looping condensins, anchors long-lived chromatin loops to create bottlebrush structures. The second, referred to as bridging condensins, forms multivalent bridges between distant parts of these loops. We show that binding of bridging condensins leads to the formation of shorter and stiffer mitotic-like cylinders without requiring any additional energy input. These cylinders have several features matching experimental observations. For instance, the axial condensin backbone breaks up into clusters as found by microscopy, and cylinder elasticity qualitatively matches that seen in chromosome pulling experiments. Additionally, simulating global condensin depletion or local faulty condensin loading gives phenotypes seen experimentally and points to a mechanistic basis for the structure of common fragile sites in mitotic chromosomes.
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Affiliation(s)
- Giada Forte
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Lora Boteva
- MRC Human Genetics Unit, Western General Hospital, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, UK
| | - Filippo Conforto
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Nick Gilbert
- MRC Human Genetics Unit, Western General Hospital, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, UK
| | - Peter R. Cook
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Davide Marenduzzo
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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5
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Kolbin D, Walker BL, Hult C, Stanton JD, Adalsteinsson D, Forest MG, Bloom K. Polymer Modeling Reveals Interplay between Physical Properties of Chromosomal DNA and the Size and Distribution of Condensin-Based Chromatin Loops. Genes (Basel) 2023; 14:2193. [PMID: 38137015 PMCID: PMC10742461 DOI: 10.3390/genes14122193] [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: 10/23/2023] [Revised: 11/28/2023] [Accepted: 12/06/2023] [Indexed: 12/24/2023] Open
Abstract
Transient DNA loops occur throughout the genome due to thermal fluctuations of DNA and the function of SMC complex proteins such as condensin and cohesin. Transient crosslinking within and between chromosomes and loop extrusion by SMCs have profound effects on high-order chromatin organization and exhibit specificity in cell type, cell cycle stage, and cellular environment. SMC complexes anchor one end to DNA with the other extending some distance and retracting to form a loop. How cells regulate loop sizes and how loops distribute along chromatin are emerging questions. To understand loop size regulation, we employed bead-spring polymer chain models of chromatin and the activity of an SMC complex on chromatin. Our study shows that (1) the stiffness of the chromatin polymer chain, (2) the tensile stiffness of chromatin crosslinking complexes such as condensin, and (3) the strength of the internal or external tethering of chromatin chains cooperatively dictate the loop size distribution and compaction volume of induced chromatin domains. When strong DNA tethers are invoked, loop size distributions are tuned by condensin stiffness. When DNA tethers are released, loop size distributions are tuned by chromatin stiffness. In this three-way interaction, the presence and strength of tethering unexpectedly dictates chromatin conformation within a topological domain.
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Affiliation(s)
- Daniel Kolbin
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.K.); (J.D.S.)
| | - Benjamin L. Walker
- Department of Mathematics, University of California-Irvine, Irvine, CA 92697, USA;
| | - Caitlin Hult
- Department of Mathematics, Gettysburg College, Gettysburg, PA 17325, USA
| | - John Donoghue Stanton
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.K.); (J.D.S.)
| | - David Adalsteinsson
- Department of Mathematics and Carolina Center for Interdisciplinary Applied Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.A.); (M.G.F.)
| | - M. Gregory Forest
- Department of Mathematics and Carolina Center for Interdisciplinary Applied Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.A.); (M.G.F.)
- Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.K.); (J.D.S.)
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6
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Tang M, Pobegalov G, Tanizawa H, Chen ZA, Rappsilber J, Molodtsov M, Noma KI, Uhlmann F. Establishment of dsDNA-dsDNA interactions by the condensin complex. Mol Cell 2023; 83:3787-3800.e9. [PMID: 37820734 PMCID: PMC10842940 DOI: 10.1016/j.molcel.2023.09.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/13/2023] [Accepted: 09/13/2023] [Indexed: 10/13/2023]
Abstract
Condensin is a structural maintenance of chromosomes (SMC) complex family member thought to build mitotic chromosomes by DNA loop extrusion. However, condensin variants unable to extrude loops, yet proficient in chromosome formation, were recently described. Here, we explore how condensin might alternatively build chromosomes. Using bulk biochemical and single-molecule experiments with purified fission yeast condensin, we observe that individual condensins sequentially and topologically entrap two double-stranded DNAs (dsDNAs). Condensin loading transitions through a state requiring DNA bending, as proposed for the related cohesin complex. While cohesin then favors the capture of a second single-stranded DNA (ssDNA), second dsDNA capture emerges as a defining feature of condensin. We provide complementary in vivo evidence for DNA-DNA capture in the form of condensin-dependent chromatin contacts within, as well as between, chromosomes. Our results support a "diffusion capture" model in which condensin acts in mitotic chromosome formation by sequential dsDNA-dsDNA capture.
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Affiliation(s)
- Minzhe Tang
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Georgii Pobegalov
- Mechanobiology and Biophysics Laboratory, The Francis Crick Institute, London NW1 1AT, UK; Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Hideki Tanizawa
- Division of Genome Biology, Institute for Genetic Medicine, Hokkaido University, Sapporo, Hokkaido 060-0815, Japan
| | - Zhuo A Chen
- Bioanalytics Unit, Institute of Biotechnology, Technische Universität Berlin, 13355 Berlin, Germany
| | - Juri Rappsilber
- Bioanalytics Unit, Institute of Biotechnology, Technische Universität Berlin, 13355 Berlin, Germany; Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Maxim Molodtsov
- Mechanobiology and Biophysics Laboratory, The Francis Crick Institute, London NW1 1AT, UK; Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Ken-Ichi Noma
- Division of Genome Biology, Institute for Genetic Medicine, Hokkaido University, Sapporo, Hokkaido 060-0815, Japan; Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK; Cell Biology Centre, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa 226-0026, Japan.
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7
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Kaur P, Lu X, Xu Q, Irvin EM, Pappas C, Zhang H, Finkelstein IJ, Shi Z, Tao YJ, Yu H, Wang H. High-speed AFM imaging reveals DNA capture and loop extrusion dynamics by cohesin-NIPBL. J Biol Chem 2023; 299:105296. [PMID: 37774974 PMCID: PMC10656236 DOI: 10.1016/j.jbc.2023.105296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 08/24/2023] [Accepted: 09/13/2023] [Indexed: 10/01/2023] Open
Abstract
3D chromatin organization plays a critical role in regulating gene expression, DNA replication, recombination, and repair. While initially discovered for its role in sister chromatid cohesion, emerging evidence suggests that the cohesin complex (SMC1, SMC3, RAD21, and SA1/SA2), facilitated by NIPBL, mediates topologically associating domains and chromatin loops through DNA loop extrusion. However, information on how conformational changes of cohesin-NIPBL drive its loading onto DNA, initiation, and growth of DNA loops is still lacking. In this study, high-speed atomic force microscopy imaging reveals that cohesin-NIPBL captures DNA through arm extension, assisted by feet (shorter protrusions), and followed by transfer of DNA to its lower compartment (SMC heads, RAD21, SA1, and NIPBL). While binding at the lower compartment, arm extension leads to the capture of a second DNA segment and the initiation of a DNA loop that is independent of ATP hydrolysis. The feet are likely contributed by the C-terminal domains of SA1 and NIPBL and can transiently bind to DNA to facilitate the loading of the cohesin complex onto DNA. Furthermore, high-speed atomic force microscopy imaging reveals distinct forward and reverse DNA loop extrusion steps by cohesin-NIPBL. These results advance our understanding of cohesin by establishing direct experimental evidence for a multistep DNA-binding mechanism mediated by dynamic protein conformational changes.
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Affiliation(s)
- Parminder Kaur
- Physics Department, North Carolina State University, Raleigh, North Carolina, USA; Center for Human Health and the Environment, North Carolina State University, Raleigh, North Carolina, USA.
| | - Xiaotong Lu
- Department of BioSciences, Rice University, Houston, Texas, USA
| | - Qi Xu
- Westlake Laboratory of Life Sciences and Biomedicine, Westlake University, Hangzhou, Zhejiang Province, P.R. China; School of Life Sciences, Westlake University, Hangzhou, Zhejiang Province, P.R. China
| | | | - Colette Pappas
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Hongshan Zhang
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, USA
| | - Ilya J Finkelstein
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, USA
| | - Zhubing Shi
- Westlake Laboratory of Life Sciences and Biomedicine, Westlake University, Hangzhou, Zhejiang Province, P.R. China; School of Life Sciences, Westlake University, Hangzhou, Zhejiang Province, P.R. China
| | - Yizhi Jane Tao
- Department of BioSciences, Rice University, Houston, Texas, USA
| | - Hongtao Yu
- Westlake Laboratory of Life Sciences and Biomedicine, Westlake University, Hangzhou, Zhejiang Province, P.R. China; School of Life Sciences, Westlake University, Hangzhou, Zhejiang Province, P.R. China
| | - Hong Wang
- Physics Department, North Carolina State University, Raleigh, North Carolina, USA; Center for Human Health and the Environment, North Carolina State University, Raleigh, North Carolina, USA; Toxicology Program, North Carolina State University, Raleigh, North Carolina, USA.
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8
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Clarence T, Robert NS, Sarigol F, Fu X, Bates PA, Simakov O. Robust 3D modeling reveals spatiosyntenic properties of animal genomes. iScience 2023; 26:106136. [PMID: 36876129 PMCID: PMC9976460 DOI: 10.1016/j.isci.2023.106136] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 11/18/2022] [Accepted: 01/31/2023] [Indexed: 02/05/2023] Open
Abstract
Animal genomes are organized into chromosomes that are remarkably conserved in their gene content, forming distinct evolutionary units (synteny). Using versatile chromosomal modeling, we infer three-dimensional topology of genomes from representative clades spanning the earliest animal diversification. We apply a partitioning approach using interaction spheres to compensate for varying quality of topological data. Using comparative genomics approaches, we test whether syntenic signal at gene pair, local, and whole chromosomal scale is reflected in the reconstructed spatial organization. We identify evolutionarily conserved three-dimensional networks at all syntenic scales revealing novel evolutionarily maintained interactors associated with known conserved local gene linkages (such as hox). We thus present evidence for evolutionary constraints that are associated with three-, rather than just two-, dimensional animal genome organization, which we term spatiosynteny. As more accurate topological data become available, together with validation approaches, spatiosynteny may become relevant in understanding the functionality behind the observed conservation of animal chromosomes.
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Affiliation(s)
- Tereza Clarence
- Biomolecular Modelling Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
- Roussos Lab/Center for Disease Neurogenomics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Corresponding author
| | - Nicolas S.M. Robert
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Fatih Sarigol
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Xiao Fu
- Biomolecular Modelling Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Paul A. Bates
- Biomolecular Modelling Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
- Corresponding author
| | - Oleg Simakov
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
- Corresponding author
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9
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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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10
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Matityahu A, Onn I. It's all in the numbers: Cohesin stoichiometry. Front Mol Biosci 2022; 9:1010894. [PMID: 36330215 PMCID: PMC9623059 DOI: 10.3389/fmolb.2022.1010894] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/05/2022] [Indexed: 01/09/2024] Open
Abstract
Cohesin, a structural maintenance of chromosome (SMC) complex, organizes chromatin into three-dimensional structures by threading chromatin into loops and stabilizing long-range chromatin interactions. Four subunits in a 1:1:1:1 ratio compose the cohesin core, which is regulated by auxiliary factors that interact with or modify the core subunits. An ongoing debate about cohesin's mechanism of action regards its stoichiometry. Namely, is cohesin activity mediated by a single complex or cooperation between several complexes that organize into dimers or oligomers? Several investigations that used various experimental approaches have tried to resolve this dispute. Some have convincingly demonstrated that the cohesin monomer is the active unit. However, others have revealed the formation of cohesin dimers and higher-order clusters on and off chromosomes. Elucidating the biological function of cohesin clusters and determining what regulates their formation are just two of the many new questions raised by these findings. We briefly review the history of the argument about cohesin stoichiometry and the central evidence for cohesin activity as a monomer vs. an oligomer. Finally, we discuss the possible biological significance of cohesin oligomerization and present open questions that remain to be answered.
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Affiliation(s)
| | - Itay Onn
- The Azrieli Faculty of Medicine, Bar-Ilan University, Ramat Gan, Safed, Israel
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11
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A phase transition for chromosome transmission when cells divide. Nature 2022; 609:35-36. [PMID: 35922488 DOI: 10.1038/d41586-022-01925-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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12
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Srinivasan D, Shisode T, Shrinet J, Fraser P. Chromosome organization through the cell cycle at a glance. J Cell Sci 2022; 135:275498. [PMID: 35608019 DOI: 10.1242/jcs.244004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genome organization and the three-dimensional folding of chromosomes are now seen as major contributors to nearly all nuclear functions including gene regulation, replication and repair. Recent studies have shown that in addition to the dramatic metamorphoses in chromosome conformation associated with entry to, and exit from mitosis, chromosomes undergo continual conformational changes throughout interphase with differential dynamics in loop structure, topological domains, compartments and lamina-associated domains. Understanding and accounting for these cell-cycle-dependent conformational changes is essential for the interpretation of data from a growing array of powerful molecular techniques to investigate genome conformation function, and to identify the molecules and mechanisms that drive chromosome conformational changes. In this Cell Science at a Glance article and the accompanying poster, we review Hi-C and microscopy studies describing cell-cycle-dependent conformational changes in chromosome structure.
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Affiliation(s)
- Divyaa Srinivasan
- Department of Biological Science, Florida State University, Tallahassee, FL 32304, USA
| | - Tarak Shisode
- Department of Biological Science, Florida State University, Tallahassee, FL 32304, USA
| | - Jatin Shrinet
- Department of Biological Science, Florida State University, Tallahassee, FL 32304, USA
| | - Peter Fraser
- Department of Biological Science, Florida State University, Tallahassee, FL 32304, USA
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13
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Kinoshita K, Tsubota Y, Tane S, Aizawa Y, Sakata R, Takeuchi K, Shintomi K, Nishiyama T, Hirano T. A loop extrusion-independent mechanism contributes to condensin I-mediated chromosome shaping. J Cell Biol 2022; 221:212966. [PMID: 35045152 PMCID: PMC8932526 DOI: 10.1083/jcb.202109016] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 11/16/2021] [Accepted: 12/23/2021] [Indexed: 12/14/2022] Open
Abstract
Condensin I is a five-subunit protein complex that is central to mitotic chromosome assembly in eukaryotic cells. Despite recent progress, its molecular mechanisms of action remain to be fully elucidated. By using Xenopus egg extracts as a functional assay, we find that condensin I complexes harboring mutations in its kleisin subunit CAP-H produce chromosomes with confined axes in the presence of topoisomerase IIα (topo IIα) and highly compact structures (termed “beans”) with condensin-positive central cores in its absence. The bean phenotype depends on the SMC ATPase cycle and can be reversed by subsequent addition of topo IIα. The HEAT repeat subunit CAP-D2, but not CAP-G, is essential for the bean formation. Notably, loop extrusion activities of the mutant complexes cannot explain the chromosomal defects they exhibit in Xenopus egg extracts, implying that a loop extrusion–independent mechanism contributes to condensin I–mediated chromosome assembly and shaping. We provide evidence that condensin–condensin interactions underlie these processes.
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Affiliation(s)
| | - Yuko Tsubota
- Division of Biological Sciences, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Shoji Tane
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
| | - Yuuki Aizawa
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
| | - Ryota Sakata
- Division of Biological Sciences, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Kozo Takeuchi
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
| | | | - Tomoko Nishiyama
- Division of Biological Sciences, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Tatsuya Hirano
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
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14
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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: 19] [Impact Index Per Article: 9.5] [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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15
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Bonato A, Michieletto D. Three-dimensional loop extrusion. Biophys J 2021; 120:5544-5552. [PMID: 34793758 PMCID: PMC8715238 DOI: 10.1016/j.bpj.2021.11.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 10/29/2021] [Accepted: 11/10/2021] [Indexed: 12/30/2022] Open
Abstract
Loop extrusion convincingly describes how certain structural maintenance of chromosome (SMC) proteins mediate the formation of large DNA loops. Yet most of the existing computational models cannot reconcile recent in vitro observations showing that condensins can traverse each other, bypass large roadblocks, and perform steps longer than their own size. To fill this gap, we propose a three-dimensional (3D) "trans-grabbing" model for loop extrusion, which not only reproduces the experimental features of loop extrusion by one SMC complex but also predicts the formation of so-called Z-loops via the interaction of two or more SMCs extruding along the same DNA substrate. By performing molecular dynamics simulations of this model, we discover that the experimentally observed asymmetry in the different types of Z-loops is a natural consequence of the DNA tethering in vitro. Intriguingly, our model predicts this bias to disappear in the absence of tethering and a third type of Z-loop, which has not yet been identified in experiments, to appear. Our model naturally explains roadblock bypassing and the appearance of steps larger than the SMC size as a consequence of non-contiguous DNA grabbing. Finally, this study is the first, to our knowledge, to address how Z-loops and bypassing might occur in a way that is broadly consistent with existing cis-only 1D loop extrusion models.
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Affiliation(s)
- Andrea Bonato
- University of Edinburgh, SUPA, School of Physics and Astronomy, Peter Guthrie Road, Edinburgh, UK
| | - Davide Michieletto
- University of Edinburgh, SUPA, School of Physics and Astronomy, Peter Guthrie Road, Edinburgh, UK; MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, UK.
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16
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Maeshima K, Iida S. The loopy world of cohesin. eLife 2021; 10:e71585. [PMID: 34309512 PMCID: PMC8313229 DOI: 10.7554/elife.71585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 07/20/2021] [Indexed: 11/23/2022] Open
Abstract
DNA loops can be formed by a mechanism in which the cohesin complex pulls DNA strands through its ring structure using biased Brownian motion.
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Affiliation(s)
- Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of GeneticsMishimaJapan
- Department of Genetics, School of Life Sciences, Sokendai (Graduate University for Advanced Studies)MishimaJapan
| | - Shiori Iida
- Genome Dynamics Laboratory, National Institute of GeneticsMishimaJapan
- Department of Genetics, School of Life Sciences, Sokendai (Graduate University for Advanced Studies)MishimaJapan
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17
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Higashi TL, Pobegalov G, Tang M, Molodtsov MI, Uhlmann F. A Brownian ratchet model for DNA loop extrusion by the cohesin complex. eLife 2021; 10:e67530. [PMID: 34309513 PMCID: PMC8313234 DOI: 10.7554/elife.67530] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 06/10/2021] [Indexed: 12/12/2022] Open
Abstract
The cohesin complex topologically encircles DNA to promote sister chromatid cohesion. Alternatively, cohesin extrudes DNA loops, thought to reflect chromatin domain formation. Here, we propose a structure-based model explaining both activities. ATP and DNA binding promote cohesin conformational changes that guide DNA through a kleisin N-gate into a DNA gripping state. Two HEAT-repeat DNA binding modules, associated with cohesin's heads and hinge, are now juxtaposed. Gripping state disassembly, following ATP hydrolysis, triggers unidirectional hinge module movement, which completes topological DNA entry by directing DNA through the ATPase head gate. If head gate passage fails, hinge module motion creates a Brownian ratchet that, instead, drives loop extrusion. Molecular-mechanical simulations of gripping state formation and resolution cycles recapitulate experimentally observed DNA loop extrusion characteristics. Our model extends to asymmetric and symmetric loop extrusion, as well as z-loop formation. Loop extrusion by biased Brownian motion has important implications for chromosomal cohesin function.
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Affiliation(s)
- Torahiko L Higashi
- Chromosome Segregation Laboratory, The Francis Crick InstituteLondonUnited Kingdom
| | - Georgii Pobegalov
- Mechanobiology and Biophysics Laboratory, The Francis Crick InstituteLondonUnited Kingdom
- Department of Physics and Astronomy, University College LondonLondonUnited Kingdom
| | - Minzhe Tang
- Chromosome Segregation Laboratory, The Francis Crick InstituteLondonUnited Kingdom
| | - Maxim I Molodtsov
- Mechanobiology and Biophysics Laboratory, The Francis Crick InstituteLondonUnited Kingdom
- Department of Physics and Astronomy, University College LondonLondonUnited Kingdom
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick InstituteLondonUnited Kingdom
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18
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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: 206] [Impact Index Per Article: 68.7] [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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19
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Kim KD. Potential roles of condensin in genome organization and beyond in fission yeast. J Microbiol 2021; 59:449-459. [PMID: 33877578 DOI: 10.1007/s12275-021-1039-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/22/2021] [Accepted: 02/23/2021] [Indexed: 11/24/2022]
Abstract
The genome is highly organized hierarchically by the function of structural maintenance of chromosomes (SMC) complex proteins such as condensin and cohesin from bacteria to humans. Although the roles of SMC complex proteins have been well characterized, their specialized roles in nuclear processes remain unclear. Condensin and cohesin have distinct binding sites and mediate long-range and short-range genomic associations, respectively, to form cell cycle-specific genome organization. Condensin can be recruited to highly expressed genes as well as dispersed repeat genetic elements, such as Pol III-transcribed genes, LTR retrotransposon, and rDNA repeat. In particular, mitotic transcription factors Ace2 and Ams2 recruit condensin to their target genes, forming centromeric clustering during mitosis. Condensin is potentially involved in various chromosomal processes such as the mobility of chromosomes, chromosome territories, DNA reannealing, and transcription factories. The current knowledge of condensin in fission yeast summarized in this review can help us understand how condensin mediates genome organization and participates in chromosomal processes in other organisms.
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Affiliation(s)
- Kyoung-Dong Kim
- Department of Systems Biotechnology, Chung-Ang University, Anseong, 17546, Republic of Korea.
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20
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Paulson JR, Hudson DF, Cisneros-Soberanis F, Earnshaw WC. Mitotic chromosomes. Semin Cell Dev Biol 2021; 117:7-29. [PMID: 33836947 PMCID: PMC8406421 DOI: 10.1016/j.semcdb.2021.03.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 03/23/2021] [Accepted: 03/23/2021] [Indexed: 01/25/2023]
Abstract
Our understanding of the structure and function of mitotic chromosomes has come a long way since these iconic objects were first recognized more than 140 years ago, though many details remain to be elucidated. In this chapter, we start with the early history of chromosome studies and then describe the path that led to our current understanding of the formation and structure of mitotic chromosomes. We also discuss some of the remaining questions. It is now well established that each mitotic chromatid consists of a central organizing region containing a so-called "chromosome scaffold" from which loops of DNA project radially. Only a few key non-histone proteins and protein complexes are required to form the chromosome: topoisomerase IIα, cohesin, condensin I and condensin II, and the chromokinesin KIF4A. These proteins are concentrated along the axis of the chromatid. Condensins I and II are primarily responsible for shaping the chromosome and the scaffold, and they produce the loops of DNA by an ATP-dependent process known as loop extrusion. Modelling of Hi-C data suggests that condensin II adopts a spiral staircase arrangement with an extruded loop extending out from each step in a roughly helical pattern. Condensin I then forms loops nested within these larger condensin II loops, thereby giving rise to the final compaction of the mitotic chromosome in a process that requires Topo IIα.
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Affiliation(s)
- James R Paulson
- Department of Chemistry, University of Wisconsin Oshkosh, 800 Algoma Boulevard, Oshkosh, WI 54901, USA.
| | - Damien F Hudson
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, VIC 3052, Australia
| | - Fernanda Cisneros-Soberanis
- Wellcome Trust Centre for Cell Biology, ICB, University of Edinburgh, Michael Swann Building, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK
| | - William C Earnshaw
- Wellcome Trust Centre for Cell Biology, ICB, University of Edinburgh, Michael Swann Building, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK.
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