1
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Roy S, Adhikary H, D’Amours D. The SMC5/6 complex: folding chromosomes back into shape when genomes take a break. Nucleic Acids Res 2024; 52:2112-2129. [PMID: 38375830 PMCID: PMC10954462 DOI: 10.1093/nar/gkae103] [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: 11/13/2023] [Revised: 01/28/2024] [Accepted: 02/01/2024] [Indexed: 02/21/2024] Open
Abstract
High-level folding of chromatin is a key determinant of the shape and functional state of chromosomes. During cell division, structural maintenance of chromosome (SMC) complexes such as condensin and cohesin ensure large-scale folding of chromatin into visible chromosomes. In contrast, the SMC5/6 complex plays more local and context-specific roles in the structural organization of interphase chromosomes with important implications for health and disease. Recent advances in single-molecule biophysics and cryo-electron microscopy revealed key insights into the architecture of the SMC5/6 complex and how interactions connecting the complex to chromatin components give rise to its unique repertoire of interphase functions. In this review, we provide an integrative view of the features that differentiates the SMC5/6 complex from other SMC enzymes and how these enable dramatic reorganization of DNA folding in space during DNA repair reactions and other genome transactions. Finally, we explore the mechanistic basis for the dynamic targeting of the SMC5/6 complex to damaged chromatin and its crucial role in human health.
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Affiliation(s)
- Shamayita Roy
- Ottawa Institute of Systems Biology, Department of Cellular and Molecular Medicine, University of Ottawa, Roger Guindon Hall, 451 Smyth Rd, Ottawa, ON K1H 8M5, Canada
| | - Hemanta Adhikary
- Ottawa Institute of Systems Biology, Department of Cellular and Molecular Medicine, University of Ottawa, Roger Guindon Hall, 451 Smyth Rd, Ottawa, ON K1H 8M5, Canada
| | - Damien D’Amours
- Ottawa Institute of Systems Biology, Department of Cellular and Molecular Medicine, University of Ottawa, Roger Guindon Hall, 451 Smyth Rd, Ottawa, ON K1H 8M5, Canada
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2
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Yoshida MM, Kinoshita K, Shintomi K, Aizawa Y, Hirano T. Regulation of condensin II by self-suppression and release mechanisms. Mol Biol Cell 2024; 35:ar21. [PMID: 38088875 PMCID: PMC10881152 DOI: 10.1091/mbc.e23-10-0392] [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: 10/10/2023] [Revised: 11/29/2023] [Accepted: 11/30/2023] [Indexed: 01/14/2024] Open
Abstract
In vertebrates, two distinct condensin complexes, condensin I and condensin II, cooperate to drive mitotic chromosome assembly. It remains largely unknown how the two complexes differentially contribute to this process at a mechanistic level. We have previously dissected the role of individual subunits of condensin II by introducing recombinant complexes into Xenopus egg extracts. Here we extend these efforts by introducing a modified functional assay using extracts depleted of topoisomerase IIα (topo IIα), which allows us to further elucidate the functional similarities and differences between condensin I and condensin II. The intrinsically disordered C-terminal region of the CAP-D3 subunit (the D3 C-tail) is a major target of Cdk1 phosphorylation, and phosphorylation-deficient mutations in this region impair condensin II functions. We also identify a unique helical structure in CAP-D3 (the D3 HEAT docker) that is predicted to directly interact with CAP-G2. Deletion of the D3 HEAT docker, along with the D3 C-tail, enhances the ability of condensin II to assemble mitotic chromosomes. Taken together, we propose a self-suppression mechanism unique to condensin II that is released by mitotic phosphorylation. Evolutionary implications of our findings are also discussed.
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Affiliation(s)
- Makoto M. Yoshida
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
| | | | - Keishi Shintomi
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
| | - Yuuki Aizawa
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
| | - Tatsuya Hirano
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
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3
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Kawasoe Y, Shimokawa S, Gillespie PJ, Blow JJ, Tsurimoto T, Takahashi TS. The Atad5 RFC-like complex is the major unloader of proliferating cell nuclear antigen in Xenopus egg extracts. J Biol Chem 2024; 300:105588. [PMID: 38141767 PMCID: PMC10827553 DOI: 10.1016/j.jbc.2023.105588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 12/04/2023] [Accepted: 12/11/2023] [Indexed: 12/25/2023] Open
Abstract
Proliferating cell nuclear antigen (PCNA) is a homo-trimeric clamp complex that serves as the molecular hub for various DNA transactions, including DNA synthesis and post-replicative mismatch repair. Its timely loading and unloading are critical for genome stability. PCNA loading is catalyzed by Replication factor C (RFC) and the Ctf18 RFC-like complex (Ctf18-RLC), and its unloading is catalyzed by Atad5/Elg1-RLC. However, RFC, Ctf18-RLC, and even some subcomplexes of their shared subunits are capable of unloading PCNA in vitro, leaving an ambiguity in the division of labor in eukaryotic clamp dynamics. By using a system that specifically detects PCNA unloading, we show here that Atad5-RLC, which accounts for only approximately 3% of RFC/RLCs, nevertheless provides the major PCNA unloading activity in Xenopus egg extracts. RFC and Ctf18-RLC each account for approximately 40% of RFC/RLCs, while immunodepletion of neither Rfc1 nor Ctf18 detectably affects the rate of PCNA unloading in our system. PCNA unloading is dependent on the ATP-binding motif of Atad5, independent of nicks on DNA and chromatin assembly, and inhibited effectively by PCNA-interacting peptides. These results support a model in which Atad5-RLC preferentially unloads DNA-bound PCNA molecules that are free from their interactors.
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Affiliation(s)
| | - Sakiko Shimokawa
- Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan
| | - Peter J Gillespie
- Division of Molecular, Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - J Julian Blow
- Division of Molecular, Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
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4
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Golfier S, Quail T, Brugués J. Single-Molecule Approaches to Study DNA Condensation. Methods Mol Biol 2024; 2740:1-19. [PMID: 38393466 DOI: 10.1007/978-1-0716-3557-5_1] [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] [Indexed: 02/25/2024]
Abstract
Proteins drive genome compartmentalization across different length scales. While the identities of these proteins have been well-studied, the physical mechanisms that drive genome organization have remained largely elusive. Studying these mechanisms is challenging owing to a lack of methodologies to parametrize physical models in cellular contexts. Furthermore, because of the complex, entangled, and dense nature of chromatin, conventional live imaging approaches often lack the spatial resolution to dissect these principles. In this chapter, we will describe how to image the interactions of λ-DNA with proteins under purified and cytoplasmic conditions. First, we will outline how to prepare biotinylated DNA, functionalize coverslips with biotin-conjugated poly-ethylene glycol (PEG), and assemble DNA microchannels compatible for the imaging of protein-DNA interactions using total internal fluorescence microscopy. Then we will describe experimental methods to image protein-DNA interactions in vitro and DNA loop extrusion using Xenopus laevis egg extracts.
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Affiliation(s)
- Stefan Golfier
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
- B CUBE, Center for Molecular Bioengineering, TU Dresden, Dresden, Germany
| | - Thomas Quail
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
- EMBL Heidelberg, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Jan Brugués
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.
- Center for Systems Biology Dresden, Dresden, Germany.
- Physics of Life, TU Dresden, Dresden, Germany.
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5
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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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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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Yamamoto T, Kinoshita K, Hirano T. Elasticity control of entangled chromosomes: Crosstalk between condensin complexes and nucleosomes. Biophys J 2023; 122:3869-3881. [PMID: 37571823 PMCID: PMC10560673 DOI: 10.1016/j.bpj.2023.08.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 07/18/2023] [Accepted: 08/08/2023] [Indexed: 08/13/2023] Open
Abstract
Condensin-mediated loop extrusion is now considered as the main driving force of mitotic chromosome assembly. Recent experiments have shown, however, that a class of mutant condensin complexes deficient in loop extrusion can assemble chromosome-like structures in Xenopus egg extracts, although these structures are somewhat different from those assembled by wild-type condensin complexes. In the absence of topoisomerase II (topo II), the mutant condensin complexes produce an unusual round-shaped structure termed a bean, which consists of a DNA-dense central core surrounded by a DNA-sparse halo. The mutant condensin complexes accumulate in the core, whereas histones are more concentrated in the halo than in the core. We consider that this peculiar structure serves as a model system to study how DNA entanglements, nucleosomes, and condensin functionally crosstalk with each other. To gain insight into how the bean structure is formed, here we construct a theoretical model. Our theory predicts that the core is formed by attractive interactions between mutant condensin complexes, whereas the halo is stabilized by the energy reduction through the selective accumulation of nucleosomes. The formation of the halo increases the elastic free energy due to the DNA entanglement in the core, but the latter free energy is compensated by condensin complexes that suppress the assembly of nucleosomes.
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Affiliation(s)
- Tetsuya Yamamoto
- Institute for Chemical Reaction Design and Discovery (ICReDD), Hokkaido University, Sapporo, Hokkaido, Japan.
| | | | - Tatsuya Hirano
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
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8
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Abstract
Many cellular processes require large-scale rearrangements of chromatin structure. Structural maintenance of chromosomes (SMC) protein complexes are molecular machines that can provide structure to chromatin. These complexes can connect DNA elements in cis, walk along DNA, build and processively enlarge DNA loops and connect DNA molecules in trans to hold together the sister chromatids. These DNA-shaping abilities place SMC complexes at the heart of many DNA-based processes, including chromosome segregation in mitosis, transcription control and DNA replication, repair and recombination. In this Review, we discuss the latest insights into how SMC complexes such as cohesin, condensin and the SMC5-SMC6 complex shape DNA to direct these fundamental chromosomal processes. We also consider how SMC complexes, by building chromatin loops, can counteract the natural tendency of alike chromatin regions to cluster. SMC complexes thus control nuclear organization by participating in a molecular tug of war that determines the architecture of our genome.
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Affiliation(s)
- Claire Hoencamp
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Benjamin D Rowland
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
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9
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Spicer MFD, Gerlich DW. The material properties of mitotic chromosomes. Curr Opin Struct Biol 2023; 81:102617. [PMID: 37279615 PMCID: PMC10448380 DOI: 10.1016/j.sbi.2023.102617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 03/28/2023] [Accepted: 05/04/2023] [Indexed: 06/08/2023]
Abstract
Chromosomes transform during the cell cycle, allowing transcription and replication during interphase and chromosome segregation during mitosis. Morphological changes are thought to be driven by the combined effects of DNA loop extrusion and a chromatin solubility phase transition. By extruding the chromatin fibre into loops, condensins enrich at an axial core and provide resistance to spindle pulling forces. Mitotic chromosomes are further compacted by deacetylation of histone tails, rendering chromatin insoluble and resistant to penetration by microtubules. Regulation of surface properties by Ki-67 allows independent chromosome movement in early mitosis and clustering during mitotic exit. Recent progress has provided insight into how the extraordinary material properties of chromatin emerge from these activities, and how these properties facilitate faithful chromosome segregation.
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Affiliation(s)
- Maximilian F D Spicer
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), 1030, Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, A-1030, Vienna, Austria. https://twitter.com/Spicer__Max
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), 1030, Vienna, Austria.
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10
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Holub M, Birnie A, Japaridze A, van der Torre J, Ridder MD, de Ram C, Pabst M, Dekker C. Extracting and characterizing protein-free megabase-pair DNA for in vitro experiments. CELL REPORTS METHODS 2022; 2:100366. [PMID: 36590691 PMCID: PMC9795359 DOI: 10.1016/j.crmeth.2022.100366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 09/29/2022] [Accepted: 11/16/2022] [Indexed: 12/15/2022]
Abstract
Chromosome structure and function is studied using various cell-based methods as well as with a range of in vitro single-molecule techniques on short DNA substrates. Here, we present a method to obtain megabase-pair-length deproteinated DNA for in vitro studies. We isolated chromosomes from bacterial cells and enzymatically digested the native proteins. Mass spectrometry indicated that 97%-100% of DNA-binding proteins are removed from the sample. Fluorescence microscopy analysis showed an increase in the radius of gyration of the DNA polymers, while the DNA length remained megabase-pair sized. In proof-of-concept experiments using these deproteinated long DNA molecules, we observed DNA compaction upon adding the DNA-binding protein Fis or PEG crowding agents and showed that it is possible to track the motion of a fluorescently labeled DNA locus. These results indicate the practical feasibility of a "genome-in-a-box" approach to study chromosome organization from the bottom up.
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Affiliation(s)
- Martin Holub
- Department of Bionanoscience & Kavli Institute for Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Anthony Birnie
- Department of Bionanoscience & Kavli Institute for Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Aleksandre Japaridze
- Department of Bionanoscience & Kavli Institute for Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Jaco van der Torre
- Department of Bionanoscience & Kavli Institute for Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Maxime den Ridder
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Carol de Ram
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Martin Pabst
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Cees Dekker
- Department of Bionanoscience & Kavli Institute for Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
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11
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Mansisidor AR, Risca VI. Chromatin accessibility: methods, mechanisms, and biological insights. Nucleus 2022; 13:236-276. [PMID: 36404679 PMCID: PMC9683059 DOI: 10.1080/19491034.2022.2143106] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/23/2022] [Accepted: 10/30/2022] [Indexed: 11/22/2022] Open
Abstract
Access to DNA is a prerequisite to the execution of essential cellular processes that include transcription, replication, chromosomal segregation, and DNA repair. How the proteins that regulate these processes function in the context of chromatin and its dynamic architectures is an intensive field of study. Over the past decade, genome-wide assays and new imaging approaches have enabled a greater understanding of how access to the genome is regulated by nucleosomes and associated proteins. Additional mechanisms that may control DNA accessibility in vivo include chromatin compaction and phase separation - processes that are beginning to be understood. Here, we review the ongoing development of accessibility measurements, we summarize the different molecular and structural mechanisms that shape the accessibility landscape, and we detail the many important biological functions that are linked to chromatin accessibility.
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Affiliation(s)
- Andrés R. Mansisidor
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
| | - Viviana I. Risca
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
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12
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Yoshida MM, Kinoshita K, Aizawa Y, Tane S, Yamashita D, Shintomi K, Hirano T. Molecular dissection of condensin II-mediated chromosome assembly using in vitro assays. eLife 2022; 11:78984. [PMID: 35983835 PMCID: PMC9433093 DOI: 10.7554/elife.78984] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Accepted: 08/11/2022] [Indexed: 11/18/2022] Open
Abstract
In vertebrates, condensin I and condensin II cooperate to assemble rod-shaped chromosomes during mitosis. Although the mechanism of action and regulation of condensin I have been studied extensively, our corresponding knowledge of condensin II remains very limited. By introducing recombinant condensin II complexes into Xenopus egg extracts, we dissect the roles of its individual subunits in chromosome assembly. We find that one of two HEAT subunits, CAP-D3, plays a crucial role in condensin II-mediated assembly of chromosome axes, whereas the other HEAT subunit, CAP-G2, has a very strong negative impact on this process. The structural maintenance of chromosomes ATPase and the basic amino acid clusters of the kleisin subunit CAP-H2 are essential for this process. Deletion of the C-terminal tail of CAP-D3 increases the ability of condensin II to assemble chromosomes and further exposes a hidden function of CAP-G2 in the lateral compaction of chromosomes. Taken together, our results uncover a multilayered regulatory mechanism unique to condensin II, and provide profound implications for the evolution of condensin II.
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Affiliation(s)
| | | | - Yuuki Aizawa
- Chromosome Dynamics Laboratory, RIKEN, Wako, Japan
| | - Shoji Tane
- Chromosome Dynamics Laboratory, RIKEN, Wako, Japan
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13
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Shintomi K. Making Mitotic Chromosomes in a Test Tube. EPIGENOMES 2022; 6:epigenomes6030020. [PMID: 35893016 PMCID: PMC9326633 DOI: 10.3390/epigenomes6030020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 07/18/2022] [Accepted: 07/18/2022] [Indexed: 02/01/2023] Open
Abstract
Mitotic chromosome assembly is an essential preparatory step for accurate transmission of the genome during cell division. During the past decades, biochemical approaches have uncovered the molecular basis of mitotic chromosomes. For example, by using cell-free assays of frog egg extracts, the condensin I complex central for the chromosome assembly process was first identified, and its functions have been intensively studied. A list of chromosome-associated proteins has been almost completed, and it is now possible to reconstitute structures resembling mitotic chromosomes with a limited number of purified factors. In this review, I introduce how far we have come in understanding the mechanism of chromosome assembly using cell-free assays and reconstitution assays, and I discuss their potential applications to solve open questions.
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Affiliation(s)
- Keishi Shintomi
- Chromosome Dynamics Laboratory, RIKEN, Wako 351-0198, Saitama, Japan
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14
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Yamamoto T, Schiessel H. Loop extrusion driven volume phase transition of entangled chromosomes. Biophys J 2022; 121:2742-2750. [PMID: 35706364 DOI: 10.1016/j.bpj.2022.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/26/2022] [Accepted: 06/09/2022] [Indexed: 11/24/2022] Open
Abstract
Experiments on reconstituted chromosomes have revealed that mitotic chromosomes are assembled even without nucleosomes. When topoisomerase II (topo II) is depleted from such reconstituted chromosomes, these chromosomes are not disentangled and form "sparklers," where DNA and linker histone are condensed in the core and condensin is localized at the periphery. To understand the mechanism of the assembly of sparklers, we here take into account the loop extrusion by condensin in an extension of the theory of entangled polymer gels. The loop extrusion stiffens an entangled DNA network because DNA segments in the elastically effective chains are translocated to loops, which are elastically ineffective. Our theory predicts that the loop extrusion by condensin drives the volume phase transition that collapses a swollen entangled DNA gel because the stiffening of the network destabilizes the swollen phase. This may be an important piece to understand the mechanism of the assembly of mitotic chromosomes.
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Affiliation(s)
- Tetsuya Yamamoto
- Institute for Chemical Reaction Design and Discovery, Hokkaido University, Sapporo, Japan.
| | - Helmut Schiessel
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
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15
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Haase J, Chen R, Parker WM, Bonner MK, Jenkins LM, Kelly AE. The TFIIH complex is required to establish and maintain mitotic chromosome structure. eLife 2022; 11:75475. [PMID: 35293859 PMCID: PMC8956287 DOI: 10.7554/elife.75475] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 03/15/2022] [Indexed: 11/13/2022] Open
Abstract
Condensins compact chromosomes to promote their equal segregation during mitosis, but the mechanism of condensin engagement with and action on chromatin is incompletely understood. Here, we show that the general transcription factor TFIIH complex is continuously required to establish and maintain a compacted chromosome structure in transcriptionally silent Xenopus egg extracts. Inhibiting the DNA-dependent ATPase activity of the TFIIH complex subunit XPB rapidly and reversibly induces a complete loss of chromosome structure and prevents the enrichment of condensins I and II, but not topoisomerase II, on chromatin. In addition, inhibiting TFIIH prevents condensation of both mouse and Xenopus nuclei in Xenopus egg extracts, which suggests an evolutionarily conserved mechanism of TFIIH action. Reducing nucleosome density through partial histone depletion restores chromosome structure and condensin enrichment in the absence of TFIIH activity. We propose that the TFIIH complex promotes mitotic chromosome condensation by dynamically altering the chromatin environment to facilitate condensin loading and condensin-dependent loop extrusion.
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Affiliation(s)
- Julian Haase
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, Bethesda, United States
| | - Richard Chen
- Graduate School of Biomedical Sciences, The University of Texas Southwestern Medical Center, Dallas, United States
| | - Wesley M Parker
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, Bethesda, United States
| | - Mary Kate Bonner
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, Bethesda, United States
| | - Lisa M Jenkins
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, Bethesda, United States
| | - Alexander E Kelly
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, Bethesda, United States
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16
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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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17
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Hiraoka Y. Chromatin Unlimited: An Evolutionary View of Chromatin. EPIGENOMES 2022; 6:epigenomes6010002. [PMID: 35076484 PMCID: PMC8788554 DOI: 10.3390/epigenomes6010002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 12/28/2021] [Indexed: 02/01/2023] Open
Affiliation(s)
- Yasushi Hiraoka
- Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
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18
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Tane S, Shintomi K, Kinoshita K, Tsubota Y, Yoshida MM, Nishiyama T, Hirano T. Cell cycle-specific loading of condensin I is regulated by the N-terminal tail of its kleisin subunit. eLife 2022; 11:84694. [PMID: 36511239 PMCID: PMC9797191 DOI: 10.7554/elife.84694] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 11/28/2022] [Indexed: 12/14/2022] Open
Abstract
Condensin I is a pentameric protein complex that plays an essential role in mitotic chromosome assembly in eukaryotic cells. Although it has been shown that condensin I loading is mitosis specific, it remains poorly understood how the robust cell cycle regulation of condensin I is achieved. Here, we set up a panel of in vitro assays to demonstrate that cell cycle-specific loading of condensin I is regulated by the N-terminal tail (N-tail) of its kleisin subunit CAP-H. Deletion of the N-tail accelerates condensin I loading and chromosome assembly in Xenopus egg mitotic extracts. Phosphorylation-deficient and phosphorylation-mimetic mutations in the CAP-H N-tail decelerate and accelerate condensin I loading, respectively. Remarkably, deletion of the N-tail enables condensin I to assemble mitotic chromosome-like structures even in interphase extracts. Together with other extract-free functional assays in vitro, our results uncover one of the multilayered mechanisms that ensure cell cycle-specific loading of condensin I onto chromosomes.
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Affiliation(s)
- Shoji Tane
- Chromosome Dynamics Laboratory, RIKENWakoJapan
| | | | | | - Yuko Tsubota
- Division of Biological Sciences, Graduate School of Science, Nagoya UniversityNagoyaJapan
| | | | - Tomoko Nishiyama
- Division of Biological Sciences, Graduate School of Science, Nagoya UniversityNagoyaJapan
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19
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Wang X, Wang L, Dou J, Yu T, Cao P, Fan N, Borjigin U, Nashun B. Distinct role of histone chaperone Asf1a and Asf1b during fertilization and pre-implantation embryonic development in mice. Epigenetics Chromatin 2021; 14:55. [PMID: 34906203 PMCID: PMC8670131 DOI: 10.1186/s13072-021-00430-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 11/30/2021] [Indexed: 11/16/2022] Open
Abstract
Background Asf1 is a well-conserved histone chaperone that regulates multiple cellular processes in different species. Two paralogous genes, Asf1a and Asf1b exist in mammals, but their role during fertilization and early embryogenesis remains to be investigated further. Methods We analyzed the dynamics of histone chaperone Asf1a and Asf1b in oocytes and pre-implantation embryos in mice by immunofluorescence and real-time quantitative PCR, and further investigated the role of Asf1a and Asf1b during fertilization and pre-implantation development by specific Morpholino oligos-mediated knock down approach. Results Immunofluorescence with specific antibodies revealed that both Asf1a and Asf1b were deposited in the nuclei of fully grown oocytes, accumulated abundantly in zygote and 2-cell embryonic nuclei, but turned low at 4-cell stage embryos. In contrast to the weak but definite nuclear deposition of Asf1a, Asf1b disappeared from embryonic nuclei at morula and blastocyst stages. The knockdown of Asf1a and Asf1b by specific Morpholino oligos revealed that Asf1a but not Asf1b was required for the histone H3.3 assembly in paternal pronucleus. However, knockdown of either Asf1a or Asf1b expression decreased developmental potential of pre-implantation embryos. Furthermore, while Asf1a KD severely reduced H3K56 acetylation level and the expression of Oct4 in blastocyst stage embryos, Asf1b KD almost eliminated nuclear accumulation of proliferating cell marker-PCNA in morula stage embryos. These results suggested that histone chaperone Asf1a and Asf1b play distinct roles during fertilization and pre-implantation development in mice. Conclusions Our data suggested that both Asf1a and Asf1b are required for pre-implantation embryonic development. Asf1a regulates H3K56ac levels and Oct4 expression, while Asf1b safeguards pre-implantation embryo development by regulating cell proliferation. We also showed that Asf1a, but not Asf1b, was necessary for the assembly of histone H3.3 in paternal pronuclei after fertilization. Supplementary Information The online version contains supplementary material available at 10.1186/s13072-021-00430-7.
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Affiliation(s)
- Xuemei Wang
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China
| | - Lu Wang
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China
| | - Jie Dou
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China
| | - Tianjiao Yu
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China
| | - Pengbo Cao
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China
| | - Na Fan
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China
| | - Uyunbilig Borjigin
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China
| | - Buhe Nashun
- State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, 24 Zhaojun Road, Yuquan District, Hohhot, 010070, Inner Mongolia, China.
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20
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Choppakatla P, Dekker B, Cutts EE, Vannini A, Dekker J, Funabiki H. Linker histone H1.8 inhibits chromatin binding of condensins and DNA topoisomerase II to tune chromosome length and individualization. eLife 2021; 10:e68918. [PMID: 34406118 PMCID: PMC8416026 DOI: 10.7554/elife.68918] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 08/13/2021] [Indexed: 12/14/2022] Open
Abstract
DNA loop extrusion by condensins and decatenation by DNA topoisomerase II (topo II) are thought to drive mitotic chromosome compaction and individualization. Here, we reveal that the linker histone H1.8 antagonizes condensins and topo II to shape mitotic chromosome organization. In vitro chromatin reconstitution experiments demonstrate that H1.8 inhibits binding of condensins and topo II to nucleosome arrays. Accordingly, H1.8 depletion in Xenopus egg extracts increased condensins and topo II levels on mitotic chromatin. Chromosome morphology and Hi-C analyses suggest that H1.8 depletion makes chromosomes thinner and longer through shortening the average loop size and reducing the DNA amount in each layer of mitotic loops. Furthermore, excess loading of condensins and topo II to chromosomes by H1.8 depletion causes hyper-chromosome individualization and dispersion. We propose that condensins and topo II are essential for chromosome individualization, but their functions are tuned by the linker histone to keep chromosomes together until anaphase.
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Affiliation(s)
- Pavan Choppakatla
- Laboratory of Chromosome and Cell Biology, The Rockefeller UniversityNew YorkUnited States
| | - Bastiaan Dekker
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical SchoolWorcesterUnited States
| | - Erin E Cutts
- Division of Structural Biology, The Institute of Cancer ResearchLondonUnited Kingdom
| | - Alessandro Vannini
- Division of Structural Biology, The Institute of Cancer ResearchLondonUnited Kingdom
- Fondazione Human Technopole, Structural Biology Research Centre, 20157MilanItaly
| | - Job Dekker
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical SchoolWorcesterUnited States
- Howard Hughes Medical InstituteChevy ChaseUnited States
| | - Hironori Funabiki
- Laboratory of Chromosome and Cell Biology, The Rockefeller UniversityNew YorkUnited States
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21
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Daban JR. Soft-matter properties of multilayer chromosomes. Phys Biol 2021; 18. [PMID: 34126606 DOI: 10.1088/1478-3975/ac0aff] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 06/14/2021] [Indexed: 12/17/2022]
Abstract
This perspective aims to identify the relationships between the structural and dynamic properties of chromosomes and the fundamental properties of soft-matter systems. Chromatin is condensed into metaphase chromosomes during mitosis. The resulting structures are elongated cylinders having micrometer-scale dimensions. Our previous studies, using transmission electron microscopy, atomic force microscopy, and cryo-electron tomography, suggested that metaphase chromosomes have a multilayered structure, in which each individual layer has the width corresponding to a mononucleosome sheet. The self-assembly of multilayer chromatin plates from small chromatin fragments suggests that metaphase chromosomes are self-organized hydrogels (in which a single DNA molecule crosslinks the whole structure) with an internal liquid-crystal order produced by the stacking of chromatin layers along the chromosome axis. This organization of chromatin was unexpected, but the spontaneous assembly of large structures has been studied in different soft-matter systems and, according to these studies, the self-organization of chromosomes could be justified by the interplay between weak interactions of repetitive nucleosome building blocks and thermal fluctuations. The low energy of interaction between relatively large building blocks also justifies the easy deformation and structural fluctuations of soft-matter structures and the changes of phase caused by diverse external factors. Consistent with these properties of soft matter, different experimental results show that metaphase chromosomes are easily deformable. Furthermore, at the end of mitosis, condensed chromosomes undergo a phase transition into a more fluid structure, which can be correlated to the decrease in the Mg2+concentration and to the dissociation of condensins from chromosomes. Presumably, the unstacking of layers and chromatin fluctuations driven by thermal energy facilitate gene expression during interphase.
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Affiliation(s)
- Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193-Bellaterra (Barcelona), Spain
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22
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Koide H, Kodera N, Bisht S, Takada S, Terakawa T. Modeling of DNA binding to the condensin hinge domain using molecular dynamics simulations guided by atomic force microscopy. PLoS Comput Biol 2021; 17:e1009265. [PMID: 34329301 PMCID: PMC8357123 DOI: 10.1371/journal.pcbi.1009265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/11/2021] [Accepted: 07/10/2021] [Indexed: 11/19/2022] Open
Abstract
The condensin protein complex compacts chromatin during mitosis using its DNA-loop extrusion activity. Previous studies proposed scrunching and loop-capture models as molecular mechanisms for the loop extrusion process, both of which assume the binding of double-strand (ds) DNA to the hinge domain formed at the interface of the condensin subunits Smc2 and Smc4. However, how the hinge domain contacts dsDNA has remained unknown. Here, we conducted atomic force microscopy imaging of the budding yeast condensin holo-complex and used this data as basis for coarse-grained molecular dynamics simulations to model the hinge structure in a transient open conformation. We then simulated the dsDNA binding to open and closed hinge conformations, predicting that dsDNA binds to the outside surface when closed and to the outside and inside surfaces when open. Our simulations also suggested that the hinge can close around dsDNA bound to the inside surface. Based on these simulation results, we speculate that the conformational change of the hinge domain might be essential for the dsDNA binding regulation and play roles in condensin-mediated DNA-loop extrusion.
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Affiliation(s)
- Hiroki Koide
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Noriyuki Kodera
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan
| | - Shveta Bisht
- Cell Biology and Biophysics Unit, Structural and Computational Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Shoji Takada
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Tsuyoshi Terakawa
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
- PREST, Japan Science and Technology Agency (JST), Kawaguchi, Japan
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23
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Shintomi K, Hirano T. Guiding functions of the C-terminal domain of topoisomerase IIα advance mitotic chromosome assembly. Nat Commun 2021; 12:2917. [PMID: 34006877 PMCID: PMC8131626 DOI: 10.1038/s41467-021-23205-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 04/20/2021] [Indexed: 12/21/2022] Open
Abstract
Topoisomerase II (topo II) is one of the six proteins essential for mitotic chromatid reconstitution in vitro. It is not fully understood, however, mechanistically how this enzyme regulates this process. In an attempt to further refine the reconstitution assay, we have found that chromosomal binding of Xenopus laevis topo IIα is sensitive to buffer conditions and depends on its C-terminal domain (CTD). Enzymological assays using circular DNA substrates supports the idea that topo IIα first resolves inter-chromatid entanglements to drive individualization and then generates intra-chromatid entanglements to promote thickening. Importantly, only the latter process requires the CTD. By using frog egg extracts, we also show that the CTD contributes to proper formation of nucleosome-depleted chromatids by competing with a linker histone for non-nucleosomal DNA. Our results demonstrate that topo IIα utilizes its CTD to deliver the enzymatic core to crowded environments created during mitotic chromatid assembly, thereby fine-tuning this process. Topoisomerase IIα (topo IIα) is critical for mitotic chromatid assembly. Here the authors report a refinement of the mitotic chromatid reconstitution assay and provide novel insights into the C-terminal domain (CTD) of topo IIα.
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Affiliation(s)
| | - Tatsuya Hirano
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan.
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24
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Studying chromosome biology with single-molecule resolution in Xenopus laevis egg extracts. Essays Biochem 2021; 65:17-26. [PMID: 33438722 PMCID: PMC8056035 DOI: 10.1042/ebc20200026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 11/16/2020] [Accepted: 11/25/2020] [Indexed: 01/11/2023]
Abstract
Cell-free extracts from Xenopus laevis eggs are a model system for studying chromosome biology. Xenopus egg extracts can be synchronised in different cell cycle stages, making them useful for studying DNA replication, DNA repair and chromosome organisation. Combining single-molecule approaches with egg extracts is an exciting development being used to reveal molecular mechanisms that are difficult to study using conventional approaches. Fluorescence-based single-molecule imaging of surface-tethered DNAs has been used to visualise labelled protein movements on stretched DNA, the dynamics of DNA–protein complexes and extract-dependent structural rearrangement of stained DNA. Force-based single-molecule techniques are an alternative approach to measure mechanics of DNA and proteins. In this essay, the details of these single-molecule techniques, and the insights into chromosome biology they provide, will be discussed.
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25
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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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26
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Birnie A, Dekker C. Genome-in-a-Box: Building a Chromosome from the Bottom Up. ACS NANO 2021; 15:111-124. [PMID: 33347266 PMCID: PMC7844827 DOI: 10.1021/acsnano.0c07397] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/16/2020] [Indexed: 05/24/2023]
Abstract
Chromosome structure and dynamics are essential for life, as the way that our genomes are spatially organized within cells is crucial for gene expression, differentiation, and genome transfer to daughter cells. There is a wide variety of methods available to study chromosomes, ranging from live-cell studies to single-molecule biophysics, which we briefly review. While these technologies have yielded a wealth of data, such studies still leave a significant gap between top-down experiments on live cells and bottom-up in vitro single-molecule studies of DNA-protein interactions. Here, we introduce "genome-in-a-box" (GenBox) as an alternative in vitro approach to build and study chromosomes, which bridges this gap. The concept is to assemble a chromosome from the bottom up by taking deproteinated genome-sized DNA isolated from live cells and subsequently add purified DNA-organizing elements, followed by encapsulation in cell-sized containers using microfluidics. Grounded in the rationale of synthetic cell research, the approach would enable to experimentally study emergent effects at the global genome level that arise from the collective action of local DNA-structuring elements. We review the various DNA-structuring elements present in nature, from nucleoid-associated proteins and SMC complexes to phase separation and macromolecular crowders. Finally, we discuss how GenBox can contribute to several open questions on chromosome structure and dynamics.
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Affiliation(s)
- Anthony Birnie
- Department of Bionanoscience, Kavli
Institute of Nanoscience Delft, Delft University
of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Cees Dekker
- Department of Bionanoscience, Kavli
Institute of Nanoscience Delft, Delft University
of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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27
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Banigan EJ, Mirny LA. The interplay between asymmetric and symmetric DNA loop extrusion. eLife 2020; 9:e63528. [PMID: 33295869 PMCID: PMC7793625 DOI: 10.7554/elife.63528] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 11/30/2020] [Indexed: 12/30/2022] Open
Abstract
Chromosome compaction is essential for reliable transmission of genetic information. Experiments suggest that ∼1000-fold compaction is driven by condensin complexes that extrude chromatin loops, by progressively collecting chromatin fiber from one or both sides of the complex to form a growing loop. Theory indicates that symmetric two-sided loop extrusion can achieve such compaction, but recent single-molecule studies (Golfier et al., 2020) observed diverse dynamics of condensins that perform one-sided, symmetric two-sided, and asymmetric two-sided extrusion. We use simulations and theory to determine how these molecular properties lead to chromosome compaction. High compaction can be achieved if even a small fraction of condensins have two essential properties: a long residence time and the ability to perform two-sided (not necessarily symmetric) extrusion. In mixtures of condensins I and II, coupling two-sided extrusion and stable chromatin binding by condensin II promotes compaction. These results provide missing connections between single-molecule observations and chromosome-scale organization.
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Affiliation(s)
- Edward J Banigan
- Department of Physics and Institute for Medical Engineering and Science, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Leonid A Mirny
- Department of Physics and Institute for Medical Engineering and Science, Massachusetts Institute of TechnologyCambridgeUnited States
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28
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Maji A, Padinhateeri R, Mitra MK. The Accidental Ally: Nucleosome Barriers Can Accelerate Cohesin-Mediated Loop Formation in Chromatin. Biophys J 2020; 119:2316-2325. [PMID: 33181117 PMCID: PMC7732762 DOI: 10.1016/j.bpj.2020.10.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/21/2020] [Accepted: 10/13/2020] [Indexed: 01/26/2023] Open
Abstract
An important question in the context of the three-dimensional organization of chromosomes is the mechanism of formation of large loops between distant basepairs. Recent experiments suggest that the formation of loops might be mediated by loop extrusion factor proteins such as cohesin. Experiments on cohesin have shown that cohesins walk diffusively on the DNA and that nucleosomes act as obstacles to the diffusion, lowering the permeability and hence reducing the effective diffusion constant. An estimation of the times required to form the loops of typical sizes seen in Hi-C experiments using these low-effective-diffusion constants leads to times that are unphysically large. The puzzle then is the following: how does a cohesin molecule diffusing on the DNA backbone achieve speeds necessary to form the large loops seen in experiments? We propose a simple answer to this puzzle and show that although at low densities, nucleosomes act as barriers to cohesin diffusion, beyond a certain concentration they can reduce loop formation times because of a subtle interplay between the nucleosome size and the mean linker length. This effect is further enhanced on considering stochastic binding kinetics of nucleosomes on the DNA backbone and leads to predictions of lower loop formation times than might be expected from a naive obstacle picture of nucleosomes.
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Affiliation(s)
- Ajoy Maji
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Mithun K Mitra
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, India.
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29
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Loop extrusion: theory meets single-molecule experiments. Curr Opin Cell Biol 2020; 64:124-138. [PMID: 32534241 DOI: 10.1016/j.ceb.2020.04.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/24/2020] [Accepted: 04/28/2020] [Indexed: 11/20/2022]
Abstract
Chromosomes are organized as chromatin loops that promote segregation, enhancer-promoter interactions, and other genomic functions. Loops were hypothesized to form by 'loop extrusion,' by which structural maintenance of chromosomes (SMC) complexes, such as condensin and cohesin, bind to chromatin, reel it in, and extrude it as a loop. However, such exotic motor activity had never been observed. Following an explosion of indirect evidence, recent single-molecule experiments directly imaged DNA loop extrusion by condensin and cohesin in vitro. These experiments observe rapid (kb/s) extrusion that requires ATP hydrolysis and stalls under pN forces. Surprisingly, condensin extrudes loops asymmetrically, challenging previous models. Extrusion by cohesin is symmetric but requires the protein Nipbl. We discuss how SMC complexes may perform their functions on chromatin in vivo.
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30
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Golfier S, Quail T, Kimura H, Brugués J. Cohesin and condensin extrude DNA loops in a cell cycle-dependent manner. eLife 2020; 9:e53885. [PMID: 32396063 PMCID: PMC7316503 DOI: 10.7554/elife.53885] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 05/11/2020] [Indexed: 12/14/2022] Open
Abstract
Loop extrusion by structural maintenance of chromosomes (SMC) complexes has been proposed as a mechanism to organize chromatin in interphase and metaphase. However, the requirements for chromatin organization in these cell cycle phases are different, and it is unknown whether loop extrusion dynamics and the complexes that extrude DNA also differ. Here, we used Xenopus egg extracts to reconstitute and image loop extrusion of single DNA molecules during the cell cycle. We show that loops form in both metaphase and interphase, but with distinct dynamic properties. Condensin extrudes DNA loops non-symmetrically in metaphase, whereas cohesin extrudes loops symmetrically in interphase. Our data show that loop extrusion is a general mechanism underlying DNA organization, with dynamic and structural properties that are biochemically regulated during the cell cycle.
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Affiliation(s)
- Stefan Golfier
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Max Planck Institute for the Physics of Complex SystemsDresdenGermany
- Centre for Systems Biology DresdenDresdenGermany
- Cluster of Excellence Physics of Life, TU DresdenDresdenGermany
| | - Thomas Quail
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Max Planck Institute for the Physics of Complex SystemsDresdenGermany
- Centre for Systems Biology DresdenDresdenGermany
- Cluster of Excellence Physics of Life, TU DresdenDresdenGermany
| | - Hiroshi Kimura
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of TechnologyYokohamaJapan
| | - Jan Brugués
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Max Planck Institute for the Physics of Complex SystemsDresdenGermany
- Centre for Systems Biology DresdenDresdenGermany
- Cluster of Excellence Physics of Life, TU DresdenDresdenGermany
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31
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Wang H, Liu Y, Yuan J, Zhang J, Han F. The condensin subunits SMC2 and SMC4 interact for correct condensation and segregation of mitotic maize chromosomes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 102:467-479. [PMID: 31816133 DOI: 10.1111/tpj.14639] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 11/23/2019] [Accepted: 11/27/2019] [Indexed: 05/22/2023]
Abstract
Structural Maintenance of Chromosomes 2 (SMC2) and Structural Maintenance of Chromosomes 4 (SMC4) are the core components of the condensin complexes, which are required for chromosome assembly and faithful segregation during cell division. Because of the crucial functions of both proteins in cell division, much work has been done in various vertebrates, but little information is known about their roles in plants. Here, we identified ZmSMC2 and ZmSMC4 in maize (Zea mays) and confirmed that ZmSMC2 associates with ZmSMC4 via their hinge domains. Immunostaining revealed that both proteins showed dynamic localization during mitosis. ZmSMC2 and ZmSMC4 are essential for proper chromosome segregation and for H3 phosphorylation at Serine 10 (H3S10ph) at pericentromeres during mitotic division. The loss of function of ZmSMC2 and ZmSMC4 enlarges mitotic chromosome volume and impairs sister chromatid separation to the opposite poles. Taken together, these findings confirm and extend the coordinated role of ZmSMC2 and ZmSMC4 in maintenance of normal chromosome architecture and accurate segregation during mitosis.
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Affiliation(s)
- Hefei Wang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yang Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jing Yuan
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jing Zhang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Fangpu Han
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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32
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Kleinschnitz K, Vießmann N, Jordan M, Heidmann SK. Condensin I is required for faithful meiosis in Drosophila males. Chromosoma 2020; 129:141-160. [PMID: 32314039 PMCID: PMC7260282 DOI: 10.1007/s00412-020-00733-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 02/17/2020] [Accepted: 02/20/2020] [Indexed: 01/03/2023]
Abstract
The heteropentameric condensin complexes play vital roles in the formation and faithful segregation of mitotic chromosomes in eukaryotes. While the different contributions of the two common condensin complexes, condensin I and condensin II, to chromosome morphology and behavior in mitosis have been thoroughly investigated, much less is known about the specific roles of the two complexes during meiotic divisions. In Drosophila melanogaster, faithful mitotic divisions depend on functional condensin I, but not on condensin II. However, meiotic divisions in Drosophila males require functional condensin II subunits. The role of condensin I during male meiosis in Drosophila has been unresolved. Here, we show that condensin I-specific subunits localize to meiotic chromatin in both meiosis I and II during Drosophila spermatogenesis. Live cell imaging reveals defects during meiotic divisions after RNAi-mediated knockdown of condensin I-specific mRNAs. This phenotype correlates with reduced male fertility and an increase in nondisjunction events both in meiosis I and meiosis II. Consistently, a reduction in male fertility was also observed after proteasome-mediated degradation of the condensin I subunit Barren. Taken together, our results demonstrate an essential role of condensin I during male meiosis in Drosophila melanogaster.
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Affiliation(s)
| | - Nina Vießmann
- Lehrstuhl für Genetik, University of Bayreuth, Bayreuth, Germany
| | - Mareike Jordan
- Lehrstuhl für Genetik, University of Bayreuth, Bayreuth, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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33
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Banigan EJ, van den Berg AA, Brandão HB, Marko JF, Mirny LA. Chromosome organization by one-sided and two-sided loop extrusion. eLife 2020; 9:e53558. [PMID: 32250245 PMCID: PMC7295573 DOI: 10.7554/elife.53558] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 04/03/2020] [Indexed: 12/19/2022] Open
Abstract
SMC complexes, such as condensin or cohesin, organize chromatin throughout the cell cycle by a process known as loop extrusion. SMC complexes reel in DNA, extruding and progressively growing DNA loops. Modeling assuming two-sided loop extrusion reproduces key features of chromatin organization across different organisms. In vitro single-molecule experiments confirmed that yeast condensins extrude loops, however, they remain anchored to their loading sites and extrude loops in a 'one-sided' manner. We therefore simulate one-sided loop extrusion to investigate whether 'one-sided' complexes can compact mitotic chromosomes, organize interphase domains, and juxtapose bacterial chromosomal arms, as can be done by 'two-sided' loop extruders. While one-sided loop extrusion cannot reproduce these phenomena, variants can recapitulate in vivo observations. We predict that SMC complexes in vivo constitute effectively two-sided motors or exhibit biased loading and propose relevant experiments. Our work suggests that loop extrusion is a viable general mechanism of chromatin organization.
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Affiliation(s)
- Edward J Banigan
- Institute for Medical Engineering & Science, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Physics, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Aafke A van den Berg
- Institute for Medical Engineering & Science, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Physics, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Hugo B Brandão
- Harvard Graduate Program in Biophysics, Harvard UniversityCambridgeUnited States
| | - John F Marko
- Departments of Molecular Biosciences and Physics & Astronomy, Northwestern UniversityEvanstonUnited States
| | - Leonid A Mirny
- Institute for Medical Engineering & Science, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Physics, Massachusetts Institute of TechnologyCambridgeUnited States
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34
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Gou LT, Lim DH, Ma W, Aubol BE, Hao Y, Wang X, Zhao J, Liang Z, Shao C, Zhang X, Meng F, Li H, Zhang X, Xu R, Li D, Rosenfeld MG, Mellon PL, Adams JA, Liu MF, Fu XD. Initiation of Parental Genome Reprogramming in Fertilized Oocyte by Splicing Kinase SRPK1-Catalyzed Protamine Phosphorylation. Cell 2020; 180:1212-1227.e14. [PMID: 32169215 DOI: 10.1016/j.cell.2020.02.020] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 12/04/2019] [Accepted: 02/07/2020] [Indexed: 01/15/2023]
Abstract
The paternal genome undergoes a massive exchange of histone with protamine for compaction into sperm during spermiogenesis. Upon fertilization, this process is potently reversed, which is essential for parental genome reprogramming and subsequent activation; however, it remains poorly understood how this fundamental process is initiated and regulated. Here, we report that the previously characterized splicing kinase SRPK1 initiates this life-beginning event by catalyzing site-specific phosphorylation of protamine, thereby triggering protamine-to-histone exchange in the fertilized oocyte. Interestingly, protamine undergoes a DNA-dependent phase transition to gel-like condensates and SRPK1-mediated phosphorylation likely helps open up such structures to enhance protamine dismissal by nucleoplasmin (NPM2) and enable the recruitment of HIRA for H3.3 deposition. Remarkably, genome-wide assay for transposase-accessible chromatin sequencing (ATAC-seq) analysis reveals that selective chromatin accessibility in both sperm and MII oocytes is largely erased in early pronuclei in a protamine phosphorylation-dependent manner, suggesting that SRPK1-catalyzed phosphorylation initiates a highly synchronized reorganization program in both parental genomes.
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Affiliation(s)
- Lan-Tao Gou
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Do-Hwan Lim
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Wubin Ma
- Howard Hughes Medical Institute, Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Brandon E Aubol
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Yajing Hao
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xin Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences-University of Chinese Academy of Sciences, Shanghai 200031, China
| | - Jun Zhao
- Transgenic and Knockout Mouse Core, University of California, San Diego, La Jolla, CA 92093, USA
| | - Zhengyu Liang
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Changwei Shao
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xuan Zhang
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Fan Meng
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Hairi Li
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xiaorong Zhang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Ruiming Xu
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Dangsheng Li
- Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Michael G Rosenfeld
- Howard Hughes Medical Institute, Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Pamela L Mellon
- Transgenic and Knockout Mouse Core, University of California, San Diego, La Jolla, CA 92093, USA; Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joseph A Adams
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Mo-Fang Liu
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences-University of Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiang-Dong Fu
- Department of Cellular and Molecular Medicine, Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
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35
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Zhou CY, Heald R. Emergent properties of mitotic chromosomes. Curr Opin Cell Biol 2020; 64:43-49. [PMID: 32151949 DOI: 10.1016/j.ceb.2020.02.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 01/21/2020] [Accepted: 02/01/2020] [Indexed: 12/27/2022]
Abstract
As a cell prepares to divide, its genetic material changes dramatically in both form and function. During interphase, a dynamic interplay between DNA compartmentalization and transcription functions to program cell identity. During mitosis, this purpose is put on hold and instead chromosomes function to facilitate their accurate segregation to daughter cells. Chromatin loops are rearranged, stacked, and compressed to form X-shaped chromosomes that are neatly aligned at the center of the mitotic spindle and ready to withstand the forces of anaphase. Many factors that contribute to mitotic chromosome assembly have now been identified, but how the plethora of molecular mechanisms operate in concert to give rise to the distinct form and physical properties of mitotic chromosomes at the cellular scale remains under active investigation. In this review, we discuss recent work that addresses a major challenge for the field: How to connect the molecular-level activities to large-scale changes in whole-chromosome architecture that determine mitotic chromosome size, shape, and function.
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Affiliation(s)
- Coral Y Zhou
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720 USA.
| | - Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720 USA.
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36
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Abstract
Structural maintenance of chromosomes (SMC) complexes are key organizers of chromosome architecture in all kingdoms of life. Despite seemingly divergent functions, such as chromosome segregation, chromosome maintenance, sister chromatid cohesion, and mitotic chromosome compaction, it appears that these complexes function via highly conserved mechanisms and that they represent a novel class of DNA translocases.
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Affiliation(s)
- Stanislau Yatskevich
- Laboratory of Molecular Biology, Medical Research Council, Cambridge University, Cambridge CB2 0QH, United Kingdom
| | - James Rhodes
- Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom;
| | - Kim Nasmyth
- Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom;
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37
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Brandão HB, Paul P, van den Berg AA, Rudner DZ, Wang X, Mirny LA. RNA polymerases as moving barriers to condensin loop extrusion. Proc Natl Acad Sci U S A 2019; 116:20489-20499. [PMID: 31548377 PMCID: PMC6789630 DOI: 10.1073/pnas.1907009116] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To separate replicated sister chromatids during mitosis, eukaryotes and prokaryotes have structural maintenance of chromosome (SMC) condensin complexes that were recently shown to organize chromosomes by a process known as DNA loop extrusion. In rapidly dividing bacterial cells, the process of separating sister chromatids occurs concomitantly with ongoing transcription. How transcription interferes with the condensin loop-extrusion process is largely unexplored, but recent experiments have shown that sites of high transcription may directionally affect condensin loop extrusion. We quantitatively investigate different mechanisms of interaction between condensin and elongating RNA polymerases (RNAPs) and find that RNAPs are likely steric barriers that can push and interact with condensins. Supported by chromosome conformation capture and chromatin immunoprecipitation for cells after transcription inhibition and RNAP degradation, we argue that translocating condensins must bypass transcribing RNAPs within ∼1 to 2 s of an encounter at rRNA genes and within ∼10 s at protein-coding genes. Thus, while individual RNAPs have little effect on the progress of loop extrusion, long, highly transcribed operons can significantly impede the extrusion process. Our data and quantitative models further suggest that bacterial condensin loop extrusion occurs by 2 independent, uncoupled motor activities; the motors translocate on DNA in opposing directions and function together to enlarge chromosomal loops, each independently bypassing steric barriers in their path. Our study provides a quantitative link between transcription and 3D genome organization and proposes a mechanism of interactions between SMC complexes and elongating transcription machinery relevant from bacteria to higher eukaryotes.
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Affiliation(s)
- Hugo B Brandão
- Graduate Program in Biophysics, Harvard University, Cambridge, MA 02138
| | - Payel Paul
- Department of Biology, Indiana University, Bloomington, IN 47405
| | - Aafke A van den Berg
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - David Z Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Xindan Wang
- Department of Biology, Indiana University, Bloomington, IN 47405;
| | - Leonid A Mirny
- Graduate Program in Biophysics, Harvard University, Cambridge, MA 02138;
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
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38
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Gurova KV. Chromatin Stability as a Target for Cancer Treatment. Bioessays 2019; 41:e1800141. [PMID: 30566250 DOI: 10.1002/bies.201800141] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 10/29/2018] [Indexed: 12/14/2022]
Abstract
In this essay, I propose that DNA-binding anti-cancer drugs work more via chromatin disruption than DNA damage. Success of long-awaited drugs targeting cancer-specific drivers is limited by the heterogeneity of tumors. Therefore, chemotherapy acting via universal targets (e.g., DNA) is still the mainstream treatment for cancer. Nevertheless, the problem with targeting DNA is insufficient efficacy due to high toxicity. I propose that this problem stems from the presumption that DNA damage is critical for the anti-cancer activity of these drugs. DNA in cells exists as chromatin, and many DNA-targeting drugs alter chromatin structure by destabilizing nucleosomes and inducing histone eviction from chromatin. This effect has been largely ignored because DNA damage is seen as the major reason for anti-cancer activity. I discuss how DNA-binding molecules destabilize chromatin, why this effect is more toxic to tumoral than normal cells, and why cells die as a result of chromatin destabilization.
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Affiliation(s)
- Katerina V Gurova
- Department of Cell Stress Biology, Roswell Park Comprehensive Cancer Center, Elm and Carlton Streets, Buffalo, NY, 14263, USA
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39
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Talbert PB, Meers MP, Henikoff S. Old cogs, new tricks: the evolution of gene expression in a chromatin context. Nat Rev Genet 2019; 20:283-297. [PMID: 30886348 DOI: 10.1038/s41576-019-0105-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Sophisticated gene-regulatory mechanisms probably evolved in prokaryotes billions of years before the emergence of modern eukaryotes, which inherited the same basic enzymatic machineries. However, the epigenomic landscapes of eukaryotes are dominated by nucleosomes, which have acquired roles in genome packaging, mitotic condensation and silencing parasitic genomic elements. Although the molecular mechanisms by which nucleosomes are displaced and modified have been described, just how transcription factors, histone variants and modifications and chromatin regulators act on nucleosomes to regulate transcription is the subject of considerable ongoing study. We explore the extent to which these transcriptional regulatory components function in the context of the evolutionarily ancient role of chromatin as a barrier to processes acting on DNA and how chromatin proteins have diversified to carry out evolutionarily recent functions that accompanied the emergence of differentiation and development in multicellular eukaryotes.
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Affiliation(s)
- Paul B Talbert
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Michael P Meers
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Steven Henikoff
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA.
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40
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Ravi M, Ramanathan S, Krishna K. Factors, mechanisms and implications of chromatin condensation and chromosomal structural maintenance through the cell cycle. J Cell Physiol 2019; 235:758-775. [PMID: 31264212 DOI: 10.1002/jcp.29038] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 06/12/2019] [Indexed: 12/16/2022]
Abstract
A series of well-orchestrated events help in the chromatin condensation and the formation of chromosomes. Apart from the formation of chromosomes, maintenance of their structure is important, especially for the cell division. The structural maintenance of chromosome (SMC) proteins, the non-SMC proteins and the SMC complexes are critical for the maintenance of chromosome structure. While condensins have roles for the DNA compaction, organization, and segregation, the cohesin functions in a cyclic manner through the cell cycle, as a "cohesin cycle." Specific mechanisms maintain the architecture of the centromere, the kinetochore and the telomeres which are in tandem with the cell cycle checkpoints. The presence of chromosomal territories and compactness differences through the length of the chromosomes might have implications on selective susceptibility of specific chromosomes for induced genotoxicity.
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Affiliation(s)
- Maddaly Ravi
- Department of Human Genetics, Faculty of Biomedical Sciences, Technology and Research, Sri Ramachandra Institute of Higher Education and Research, Porur, Chennai, India
| | - Srishti Ramanathan
- Department of Human Genetics, Faculty of Biomedical Sciences, Technology and Research, Sri Ramachandra Institute of Higher Education and Research, Porur, Chennai, India
| | - Krupa Krishna
- Department of Human Genetics, Faculty of Biomedical Sciences, Technology and Research, Sri Ramachandra Institute of Higher Education and Research, Porur, Chennai, India
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41
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Batty P, Gerlich DW. Mitotic Chromosome Mechanics: How Cells Segregate Their Genome. Trends Cell Biol 2019; 29:717-726. [PMID: 31230958 DOI: 10.1016/j.tcb.2019.05.007] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/23/2019] [Accepted: 05/23/2019] [Indexed: 01/09/2023]
Abstract
During mitosis, replicated chromosomes segregate such that each daughter cell receives one copy of the genome. Faithful mechanical transport during mitosis requires that chromosomes undergo extensive structural changes as the cell cycle progresses, resulting in the formation of compact, cylindrical bodies. Such structural changes encompass a range of different activities, including longitudinal condensation of the chromosome axis, global chromatin compaction, resolution of sister chromatids, and individualisation of chromosomes into separate bodies. After mitosis, chromosomes undergo further reorganisation to rebuild interphase cell nuclei. Here we review the requirements for mitotic chromosomes to successfully transmit genetic information to daughter cells and the biophysical principles that underpin such requirements.
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Affiliation(s)
- Paul Batty
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), 1030 Vienna, Austria.
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42
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Guérin TM, Béneut C, Barinova N, López V, Lazar-Stefanita L, Deshayes A, Thierry A, Koszul R, Dubrana K, Marcand S. Condensin-Mediated Chromosome Folding and Internal Telomeres Drive Dicentric Severing by Cytokinesis. Mol Cell 2019; 75:131-144.e3. [PMID: 31204167 DOI: 10.1016/j.molcel.2019.05.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 02/12/2019] [Accepted: 05/13/2019] [Indexed: 12/13/2022]
Abstract
In Saccharomyces cerevisiae, dicentric chromosomes stemming from telomere fusions preferentially break at the fusion. This process restores a normal karyotype and protects chromosomes from the detrimental consequences of accidental fusions. Here, we address the molecular basis of this rescue pathway. We observe that tandem arrays tightly bound by the telomere factor Rap1 or a heterologous high-affinity DNA binding factor are sufficient to establish breakage hotspots, mimicking telomere fusions within dicentrics. We also show that condensins generate forces sufficient to rapidly refold dicentrics prior to breakage by cytokinesis and are essential to the preferential breakage at telomere fusions. Thus, the rescue of fused telomeres results from a condensin- and Rap1-driven chromosome folding that favors fusion entrapment where abscission takes place. Because a close spacing between the DNA-bound Rap1 molecules is essential to this process, Rap1 may act by stalling condensins.
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Affiliation(s)
- Thomas M Guérin
- CEA Paris-Saclay, Unité Stabilité Génétique Cellules Souches et Radiations, INSERM U1274, Université de Paris, Université Paris-Saclay, Fontenay-aux-roses, France
| | - Claire Béneut
- CEA Paris-Saclay, Unité Stabilité Génétique Cellules Souches et Radiations, INSERM U1274, Université de Paris, Université Paris-Saclay, Fontenay-aux-roses, France
| | - Natalja Barinova
- CEA Paris-Saclay, Unité Stabilité Génétique Cellules Souches et Radiations, INSERM U1274, Université de Paris, Université Paris-Saclay, Fontenay-aux-roses, France
| | - Virginia López
- CEA Paris-Saclay, Unité Stabilité Génétique Cellules Souches et Radiations, INSERM U1274, Université de Paris, Université Paris-Saclay, Fontenay-aux-roses, France
| | - Luciana Lazar-Stefanita
- Institut Pasteur, Unité Régulation Spatiale des Génomes, CNRS UMR 3525, Sorbonne Université, Paris, France
| | - Alice Deshayes
- CEA Paris-Saclay, Unité Stabilité Génétique Cellules Souches et Radiations, INSERM U1274, Université de Paris, Université Paris-Saclay, Fontenay-aux-roses, France
| | - Agnès Thierry
- Institut Pasteur, Unité Régulation Spatiale des Génomes, CNRS UMR 3525, Sorbonne Université, Paris, France
| | - Romain Koszul
- Institut Pasteur, Unité Régulation Spatiale des Génomes, CNRS UMR 3525, Sorbonne Université, Paris, France
| | - Karine Dubrana
- CEA Paris-Saclay, Unité Stabilité Génétique Cellules Souches et Radiations, INSERM U1274, Université de Paris, Université Paris-Saclay, Fontenay-aux-roses, France
| | - Stéphane Marcand
- CEA Paris-Saclay, Unité Stabilité Génétique Cellules Souches et Radiations, INSERM U1274, Université de Paris, Université Paris-Saclay, Fontenay-aux-roses, France.
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43
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Loop formation by SMC complexes: turning heads, bending elbows, and fixed anchors. Curr Opin Genet Dev 2019; 55:11-18. [PMID: 31108424 DOI: 10.1016/j.gde.2019.04.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 04/03/2019] [Accepted: 04/15/2019] [Indexed: 11/24/2022]
Abstract
From the dynamic interphase genome to compacted mitotic chromosomes, DNA is organized by the conserved SMC complexes cohesin and condensin. The picture is emerging that these complexes structure the genome through a shared basic principle that involves the formation and processive enlargement of chromatin loops. This appears to be an asymmetric process, in which the complex anchors at the base of a loop and then enlarges the loop in a one-sided manner. We discuss the latest insights into how ATPase-driven conformational changes within these complexes may enlarge loops, and consider how asymmetric DNA reeling can bring together genomic elements in a symmetric manner.
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Takahashi M, Hirota T. Folding the genome into mitotic chromosomes. Curr Opin Cell Biol 2019; 60:19-26. [PMID: 30999230 DOI: 10.1016/j.ceb.2019.03.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 03/02/2019] [Accepted: 03/06/2019] [Indexed: 10/27/2022]
Abstract
How linear DNA molecules are packaged into compact cylindrical chromosomes in preparation for cell division has remained one of the central outstanding questions in cell biology. Condensin is a highly conserved protein complex that universally determines large-scale DNA geometry during mitotic chromosome assembly. A wide range of recently developed approaches, including super resolution microscopy, single molecule imaging, Hi-C analyses and computational modeling, have profoundly changed how we view mitotic chromosomes. This review highlights recent discoveries on chromosome architecture and condensin function.
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Affiliation(s)
- Motoko Takahashi
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research (JFCR), Tokyo, Japan
| | - Toru Hirota
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research (JFCR), Tokyo, Japan.
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Ohta S, Taniguchi T, Sato N, Hamada M, Taniguchi H, Rappsilber J. Quantitative Proteomics of the Mitotic Chromosome Scaffold Reveals the Association of BAZ1B with Chromosomal Axes. Mol Cell Proteomics 2019; 18:169-181. [PMID: 30266865 PMCID: PMC6356081 DOI: 10.1074/mcp.ra118.000923] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 09/13/2018] [Indexed: 01/28/2023] Open
Abstract
In mitosis, chromosomes achieve their characteristic shape through condensation, an essential process for proper segregation of the genome during cell division. A classical model for mitotic chromosome condensation proposes that non-histone proteins act as a structural framework called the chromosome scaffold. The components of the chromosome scaffold, such as DNA topoisomerase IIα (TOP2A) and structural maintenance of chromosomes protein 2 (SMC2), are necessary to generate stable mitotic chromosomes; however, the existence of this scaffold remains controversial. The aim of this study was to determine the protein composition of the chromosome scaffold. We used the DT40 chicken cell line to isolate mitotic chromosomes and extract the associated protein fraction, which could contain the chromosome scaffold. MS revealed a novel component of the chromosome scaffold, bromodomain adjacent to zinc finger 1B (BAZ1B), which was localized to the mitotic chromosome axis. Knocking out BAZ1B caused prophase delay because of altered chromosome condensation timing and mitosis progression errors, and the effect was aggravated if BAZ1A, a BAZ1B homolog, was simultaneously knocked out; however, protein composition of prometaphase chromosomes was normal. Our results suggest that BAZ1 proteins are essential for timely chromosome condensation at mitosis entry. Further characterization of the functional role of BAZ1 proteins would provide new insights into the timing of chromosome condensation.
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Affiliation(s)
- Shinya Ohta
- Department of Biochemistry, Medical School, Kochi University, Kohasu, Oko-cho, Nankoku, Kochi 783-8505, Japan;.
| | - Takako Taniguchi
- Institute for Enzyme Research, Tokushima University, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Nobuko Sato
- Department of Biochemistry, Medical School, Kochi University, Kohasu, Oko-cho, Nankoku, Kochi 783-8505, Japan
| | - Mayako Hamada
- Department of Biochemistry, Medical School, Kochi University, Kohasu, Oko-cho, Nankoku, Kochi 783-8505, Japan
| | - Hisaaki Taniguchi
- Institute for Enzyme Research, Tokushima University, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Juri Rappsilber
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, 13355 Berlin, Germany;; Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, UK
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Shindo Y, Amodeo AA. Dynamics of Free and Chromatin-Bound Histone H3 during Early Embryogenesis. Curr Biol 2019; 29:359-366.e4. [DOI: 10.1016/j.cub.2018.12.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/29/2018] [Accepted: 12/13/2018] [Indexed: 11/27/2022]
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Soeda S, Yamada-Nomoto K, Michiue T, Ohsugi M. RSK-MASTL Pathway Delays Meiotic Exit in Mouse Zygotes to Ensure Paternal Chromosome Stability. Dev Cell 2018; 47:363-376.e5. [DOI: 10.1016/j.devcel.2018.09.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 06/25/2018] [Accepted: 09/09/2018] [Indexed: 11/30/2022]
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Lawrimore J, Doshi A, Friedman B, Yeh E, Bloom K. Geometric partitioning of cohesin and condensin is a consequence of chromatin loops. Mol Biol Cell 2018; 29:2737-2750. [PMID: 30207827 PMCID: PMC6249845 DOI: 10.1091/mbc.e18-02-0131] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 08/13/2018] [Accepted: 09/04/2018] [Indexed: 12/29/2022] Open
Abstract
SMC (structural maintenance of chromosomes) complexes condensin and cohesin are crucial for proper chromosome organization. Condensin has been reported to be a mechanochemical motor capable of forming chromatin loops, while cohesin passively diffuses along chromatin to tether sister chromatids. In budding yeast, the pericentric region is enriched in both condensin and cohesin. As in higher-eukaryotic chromosomes, condensin is localized to the axial chromatin of the pericentric region, while cohesin is enriched in the radial chromatin. Thus, the pericentric region serves as an ideal model for deducing the role of SMC complexes in chromosome organization. We find condensin-mediated chromatin loops establish a robust chromatin organization, while cohesin limits the area that chromatin loops can explore. Upon biorientation, extensional force from the mitotic spindle aggregates condensin-bound chromatin from its equilibrium position to the axial core of pericentric chromatin, resulting in amplified axial tension. The axial localization of condensin depends on condensin's ability to bind to chromatin to form loops, while the radial localization of cohesin depends on cohesin's ability to diffuse along chromatin. The different chromatin-tethering modalities of condensin and cohesin result in their geometric partitioning in the presence of an extensional force on chromatin.
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Affiliation(s)
- Josh Lawrimore
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Ayush Doshi
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Brandon Friedman
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Elaine Yeh
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Kerry Bloom
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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Heald R, Gibeaux R. Subcellular scaling: does size matter for cell division? Curr Opin Cell Biol 2018; 52:88-95. [PMID: 29501026 PMCID: PMC5988940 DOI: 10.1016/j.ceb.2018.02.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 02/05/2018] [Accepted: 02/13/2018] [Indexed: 12/14/2022]
Abstract
Among different species or cell types, or during early embryonic cell divisions that occur in the absence of cell growth, the size of subcellular structures, including the nucleus, chromosomes, and mitotic spindle, scale with cell size. Maintaining correct subcellular scales is thought to be important for many cellular processes and, in particular, for mitosis. In this review, we provide an update on nuclear and chromosome scaling mechanisms and their significance in metazoans, with a focus on Caenorhabditis elegans, Xenopus and mammalian systems, for which a common role for the Ran (Ras-related nuclear protein)-dependent nuclear transport system has emerged.
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Affiliation(s)
- Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
| | - Romain Gibeaux
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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