1
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Cimini D. Twenty years of merotelic kinetochore attachments: a historical perspective. Chromosome Res 2023; 31:18. [PMID: 37466740 PMCID: PMC10411636 DOI: 10.1007/s10577-023-09727-7] [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: 05/01/2023] [Revised: 06/20/2023] [Accepted: 07/08/2023] [Indexed: 07/20/2023]
Abstract
Micronuclei, small DNA-containing structures separate from the main nucleus, were used for decades as an indicator of genotoxic damage. Micronuclei containing whole chromosomes were considered a biomarker of aneuploidy and were believed to form, upon mitotic exit, from chromosomes that lagged behind in anaphase as all other chromosomes segregated to the poles of the mitotic spindle. However, the mechanism responsible for inducing anaphase lagging chromosomes remained unknown until just over twenty years ago. Here, I summarize what preceded and what followed this discovery, highlighting some of the open questions and opportunities for future investigation.
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Affiliation(s)
- Daniela Cimini
- Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, 24061, USA.
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2
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Rocha H, Simões PA, Budrewicz J, Lara-Gonzalez P, Carvalho AX, Dumont J, Desai A, Gassmann R. Nuclear-enriched protein phosphatase 4 ensures outer kinetochore assembly prior to nuclear dissolution. J Cell Biol 2023; 222:213846. [PMID: 36719399 PMCID: PMC9930252 DOI: 10.1083/jcb.202208154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 12/15/2022] [Accepted: 01/05/2023] [Indexed: 02/01/2023] Open
Abstract
A landmark event in the transition from interphase to mitosis in metazoans is nuclear envelope breakdown (NEBD). Important mitotic events occur prior to NEBD, including condensation of replicated chromosomes and assembly of kinetochores to rapidly engage spindle microtubules. Here, we show that nuclear-enriched protein phosphatase 4 (PP4) ensures robust assembly of the microtubule-coupling outer kinetochore prior to NEBD. In the absence of PP4, chromosomes exhibit extended monopolar orientation after NEBD and subsequently mis-segregate. A secondary consequence of diminished outer kinetochore assembly is defective sister chromatid resolution. After NEBD, a cytoplasmic activity compensates for PP4 loss, leading to outer kinetochore assembly and recovery of chromosomes from monopolar orientation to significant bi-orientation. The Ndc80-Ska microtubule-binding module of the outer kinetochore is required for this recovery. PP4 associates with the inner kinetochore protein CENP-C; however, disrupting the PP4-CENP-C interaction does not perturb chromosome segregation. These results establish that PP4-dependent outer kinetochore assembly prior to NEBD is critical for timely and proper engagement of chromosomes with spindle microtubules.
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Affiliation(s)
- Helder Rocha
- https://ror.org/05qpmg879Instituto de Investigação e Inovação em Saúde – i3S, Universidade do Porto, Porto, Portugal,Instituto de Biologia Molecular e Celular – IBMC, Universidade do Porto, Porto, Portugal
| | - Patrícia A. Simões
- https://ror.org/05qpmg879Instituto de Investigação e Inovação em Saúde – i3S, Universidade do Porto, Porto, Portugal,Instituto de Biologia Molecular e Celular – IBMC, Universidade do Porto, Porto, Portugal
| | - Jacqueline Budrewicz
- Ludwig Institute for Cancer Research, San Diego Branch, La Jolla, CA, USA,Division of Biological Sciences, Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
| | - Pablo Lara-Gonzalez
- Ludwig Institute for Cancer Research, San Diego Branch, La Jolla, CA, USA,Division of Biological Sciences, Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
| | - Ana Xavier Carvalho
- https://ror.org/05qpmg879Instituto de Investigação e Inovação em Saúde – i3S, Universidade do Porto, Porto, Portugal,Instituto de Biologia Molecular e Celular – IBMC, Universidade do Porto, Porto, Portugal
| | - Julien Dumont
- https://ror.org/02c5gc203Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Arshad Desai
- Ludwig Institute for Cancer Research, San Diego Branch, La Jolla, CA, USA,Division of Biological Sciences, Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
| | - Reto Gassmann
- https://ror.org/05qpmg879Instituto de Investigação e Inovação em Saúde – i3S, Universidade do Porto, Porto, Portugal,Instituto de Biologia Molecular e Celular – IBMC, Universidade do Porto, Porto, Portugal
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3
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Wang Y, Wu L, Yuen KWY. The roles of transcription, chromatin organisation and chromosomal processes in holocentromere establishment and maintenance. Semin Cell Dev Biol 2022; 127:79-89. [PMID: 35042676 DOI: 10.1016/j.semcdb.2022.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 01/09/2022] [Accepted: 01/09/2022] [Indexed: 12/15/2022]
Abstract
The centromere is a unique functional region on each eukaryotic chromosome where the kinetochore assembles and orchestrates microtubule attachment and chromosome segregation. Unlike monocentromeres that occupy a specific region on the chromosome, holocentromeres are diffused along the length of the chromosome. Despite being less common, holocentromeres have been verified in almost 800 nematode, insect, and plant species. Understanding of the molecular and epigenetic regulation of holocentromeres is lagging that of monocentromeres. Here we review how permissive locations for holocentromeres are determined across the genome, potentially by chromatin organisation, transcription, and non-coding RNAs, specifically in the nematode C. elegans. In addition, we discuss how holocentric CENP-A or CENP-T-containing nucleosomes are recruited and deposited, through the help of histone chaperones, licensing factors, and condensin complexes, both during de novo holocentromere establishment, and in each mitotic cell cycle. The process of resolving sister centromeres after DNA replication in holocentric organisms is also mentioned. Conservation and diversity between holocentric and monocentric organisms are highlighted, and outstanding questions are proposed.
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Affiliation(s)
- Yue Wang
- School of Biological Sciences, The University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong
| | - Lillian Wu
- School of Biological Sciences, The University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong; Epigenetics and Genome Stability Team, The Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom
| | - Karen Wing Yee Yuen
- School of Biological Sciences, The University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong.
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4
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Senaratne AP, Cortes-Silva N, Drinnenberg IA. Evolution of holocentric chromosomes: Drivers, diversity, and deterrents. Semin Cell Dev Biol 2022; 127:90-99. [PMID: 35031207 DOI: 10.1016/j.semcdb.2022.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 12/14/2021] [Accepted: 01/05/2022] [Indexed: 02/06/2023]
Abstract
Centromeres are specialized chromosomal regions that recruit kinetochore proteins and mediate spindle microtubule attachment to ensure faithful chromosome segregation during mitosis and meiosis. Centromeres can be restricted to one region of the chromosome. Named "monocentromere", this type represents the most commonly found centromere organization across eukaryotes. Alternatively, centromeres can also be assembled at sites chromosome-wide. This second type is called "holocentromere". Despite their early description over 100 years ago, research on holocentromeres has lagged behind that of monocentromeres. Nevertheless, the application of next generation sequencing approaches and advanced microscopic technologies enabled recent advances understanding the molecular organization and regulation of holocentromeres in different organisms. Here we review the current state of research on holocentromeres focusing on evolutionary considerations. First, we provide a brief historical perspective on the discovery of holocentric chromosomes. We then discuss models/drivers that have been proposed over the years to explain the evolutionary transition from mono- to holocentric chromosomes. We continue to review the description of holocentric chromosomes in diverse eukaryotic groups and then focus our discussion on a specific and recently characterized type of holocentromere organization in insects that functions independently of the otherwise essential centromeric marker protein CenH3, thus providing novel insights into holocentromere evolution in insects. Finally, we propose reasons to explain why the holocentric trait is not more frequent across eukaryotes despite putative selective advantages.
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Affiliation(s)
| | - Nuria Cortes-Silva
- Wellcome Trust/Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge CB2 1QN, UK; Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Ines A Drinnenberg
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France; Sorbonne Université, Institut Curie, CNRS, UMR3664, F-75005 Paris, France.
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5
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Wenda JM, Prosée RF, Gabus C, Steiner FA. Mitotic chromosome condensation requires phosphorylation of the centromeric protein KNL-2 in C. elegans. J Cell Sci 2021; 134:272713. [PMID: 34734636 PMCID: PMC8714079 DOI: 10.1242/jcs.259088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 10/25/2021] [Indexed: 11/20/2022] Open
Abstract
Centromeres are chromosomal regions that serve as sites for kinetochore formation and microtubule attachment, processes that are essential for chromosome segregation during mitosis. Centromeres are almost universally defined by the histone variant CENP-A. In the holocentric nematode C. elegans, CENP-A deposition depends on the loading factor KNL-2. Depletion of either CENP-A or KNL-2 results in defects in centromere maintenance, chromosome condensation and kinetochore formation, leading to chromosome segregation failure. Here, we show that KNL-2 is phosphorylated by CDK-1 in vitro, and that mutation of three C-terminal phosphorylation sites causes chromosome segregation defects and an increase in embryonic lethality. In strains expressing phosphodeficient KNL-2, CENP-A and kinetochore proteins are properly localised, indicating that the role of KNL-2 in centromere maintenance is not affected. Instead, the mutant embryos exhibit reduced mitotic levels of condensin II on chromosomes and significant chromosome condensation impairment. Our findings separate the functions of KNL-2 in CENP-A loading and chromosome condensation, and demonstrate that KNL-2 phosphorylation regulates the cooperation between centromeric regions and the condensation machinery in C. elegans. This article has an associated First Person interview with the first author of the paper. Summary: Phosphorylation of the essential centromere protein KNL-2 is required for mitotic chromosome condensation, but not for the role of KNL-2 in centromere maintenance and kinetochore formation.
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Affiliation(s)
- Joanna M Wenda
- Department of Molecular Biology and Institute for Genetics and Genomics in Geneva, Section of Biology, Faculty of Sciences, University of Geneva, 1211 Geneva, Switzerland
| | - Reinier F Prosée
- Department of Molecular Biology and Institute for Genetics and Genomics in Geneva, Section of Biology, Faculty of Sciences, University of Geneva, 1211 Geneva, Switzerland
| | - Caroline Gabus
- Department of Molecular Biology and Institute for Genetics and Genomics in Geneva, Section of Biology, Faculty of Sciences, University of Geneva, 1211 Geneva, Switzerland
| | - Florian A Steiner
- Department of Molecular Biology and Institute for Genetics and Genomics in Geneva, Section of Biology, Faculty of Sciences, University of Geneva, 1211 Geneva, Switzerland
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6
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Gartner A, Engebrecht J. DNA repair, recombination, and damage signaling. Genetics 2021; 220:6522877. [PMID: 35137093 PMCID: PMC9097270 DOI: 10.1093/genetics/iyab178] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 10/10/2021] [Indexed: 01/09/2023] Open
Abstract
DNA must be accurately copied and propagated from one cell division to the next, and from one generation to the next. To ensure the faithful transmission of the genome, a plethora of distinct as well as overlapping DNA repair and recombination pathways have evolved. These pathways repair a large variety of lesions, including alterations to single nucleotides and DNA single and double-strand breaks, that are generated as a consequence of normal cellular function or by external DNA damaging agents. In addition to the proteins that mediate DNA repair, checkpoint pathways have also evolved to monitor the genome and coordinate the action of various repair pathways. Checkpoints facilitate repair by mediating a transient cell cycle arrest, or through initiation of cell suicide if DNA damage has overwhelmed repair capacity. In this chapter, we describe the attributes of Caenorhabditis elegans that facilitate analyses of DNA repair, recombination, and checkpoint signaling in the context of a whole animal. We review the current knowledge of C. elegans DNA repair, recombination, and DNA damage response pathways, and their role during development, growth, and in the germ line. We also discuss how the analysis of mutational signatures in C. elegans is helping to inform cancer mutational signatures in humans.
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Affiliation(s)
- Anton Gartner
- Department for Biological Sciences, IBS Center for Genomic Integrity, Ulsan National Institute of Science and Technology, Ulsan 689-798, Republic of Korea,Corresponding author: (A.G.); (J.E.)
| | - JoAnne Engebrecht
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA 95616, USA,Corresponding author: (A.G.); (J.E.)
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7
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Herbette M, Robert V, Bailly A, Gely L, Feil R, Llères D, Palladino F. A Role for Caenorhabditis elegans COMPASS in Germline Chromatin Organization. Cells 2020; 9:cells9092049. [PMID: 32911802 PMCID: PMC7565041 DOI: 10.3390/cells9092049] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/02/2020] [Accepted: 09/03/2020] [Indexed: 02/07/2023] Open
Abstract
Deposition of histone H3 lysine 4 (H3K4) methylation at promoters is catalyzed by the SET1/COMPASS complex and is associated with context-dependent effects on gene expression and local changes in chromatin organization. The role of SET1/COMPASS in shaping chromosome architecture has not been investigated. Here we used Caenorhabditis elegans to address this question through a live imaging approach and genetic analysis. Using quantitative FRET (Förster resonance energy transfer)-based fluorescence lifetime imaging microscopy (FLIM) on germ cells expressing histones eGFP-H2B and mCherry-H2B, we find that SET1/COMPASS influences meiotic chromosome organization, with marked effects on the close proximity between nucleosomes. We further show that inactivation of set-2, encoding the C. elegans SET1 homologue, or CFP-1, encoding the chromatin targeting subunit of COMPASS, enhances germline chromosome organization defects and sterility of condensin-II depleted animals. set-2 loss also aggravates germline defects resulting from conditional inactivation of topoisomerase II, another structural component of chromosomes. Expression profiling of set-2 mutant germlines revealed only minor transcriptional changes, suggesting that the observed effects are at least partly independent of transcription. Altogether, our results are consistent with a role for SET1/COMPASS in shaping meiotic chromosomes in C. elegans, together with the non-histone proteins condensin-II and topoisomerase. Given the high degree of conservation, our findings expand the range of functions attributed to COMPASS and suggest a broader role in genome organization in different species.
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Affiliation(s)
- Marion Herbette
- Laboratory of Biology and Modeling of the Cell (LBMC), CNRS, Ecole Normale Supérieure de Lyon, Université de Lyon, 69007 Lyon, France; (M.H.); (V.R.); (L.G.)
| | - Valérie Robert
- Laboratory of Biology and Modeling of the Cell (LBMC), CNRS, Ecole Normale Supérieure de Lyon, Université de Lyon, 69007 Lyon, France; (M.H.); (V.R.); (L.G.)
| | - Aymeric Bailly
- Centre de Recherche en Biologie cellulaire de Montpellier, CRBM, CNRS, University of Montpellier, 34090 Montpellier, France;
| | - Loïc Gely
- Laboratory of Biology and Modeling of the Cell (LBMC), CNRS, Ecole Normale Supérieure de Lyon, Université de Lyon, 69007 Lyon, France; (M.H.); (V.R.); (L.G.)
| | - Robert Feil
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, 34090 Montpellier, France; (R.F.); (D.L.)
| | - David Llères
- Institute of Molecular Genetics of Montpellier (IGMM), CNRS, University of Montpellier, 34090 Montpellier, France; (R.F.); (D.L.)
| | - Francesca Palladino
- Laboratory of Biology and Modeling of the Cell (LBMC), CNRS, Ecole Normale Supérieure de Lyon, Université de Lyon, 69007 Lyon, France; (M.H.); (V.R.); (L.G.)
- Correspondence: ; Tel.: +33-047-2728-126
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8
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Hori T, Fukagawa T. Artificial generation of centromeres and kinetochores to understand their structure and function. Exp Cell Res 2020; 389:111898. [PMID: 32035949 DOI: 10.1016/j.yexcr.2020.111898] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 01/18/2020] [Accepted: 02/05/2020] [Indexed: 01/19/2023]
Abstract
The centromere is an essential genomic region that provides the surface to form the kinetochore, which binds to the spindle microtubes to mediate chromosome segregation during mitosis and meiosis. Centromeres of most organisms possess highly repetitive sequences, making it difficult to study these loci. However, an unusual centromere called a "neocentromere," which does not contain repetitive sequences, was discovered in a patient and can be generated experimentally. Recent advances in genome biology techniques allow us to analyze centromeric chromatin using neocentromeres. In addition to neocentromeres, artificial kinetochores have been generated on non-centromeric loci, using protein tethering systems. These are powerful tools to understand the mechanism of the centromere specification and kinetochore assembly. In this review, we introduce recent studies utilizing the neocentromeres and artificial kinetochores and discuss current problems in centromere biology.
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Affiliation(s)
- Tetsuya Hori
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan.
| | - Tatsuo Fukagawa
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan.
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9
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Chromosome Segregation: The Bigger They Come, the Harder They Fall. Curr Biol 2018; 28:R665-R667. [PMID: 29870706 DOI: 10.1016/j.cub.2018.04.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aneuploidy is frequently found to affect individual chromosomes differentially, but it is unclear whether this depends on inter-chromosome differences in missegregation rates. A new study presents evidence that, in the Indian muntjac, centromere-kinetochore size influences the rate at which chromosomes missegregate.
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10
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Drpic D, Almeida AC, Aguiar P, Renda F, Damas J, Lewin HA, Larkin DM, Khodjakov A, Maiato H. Chromosome Segregation Is Biased by Kinetochore Size. Curr Biol 2018; 28:1344-1356.e5. [PMID: 29706521 PMCID: PMC5954971 DOI: 10.1016/j.cub.2018.03.023] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 02/02/2018] [Accepted: 03/13/2018] [Indexed: 11/30/2022]
Abstract
Chromosome missegregation during mitosis or meiosis is a hallmark of cancer and the main cause of prenatal death in humans. The gain or loss of specific chromosomes is thought to be random, with cell viability being essentially determined by selection. Several established pathways including centrosome amplification, sister-chromatid cohesion defects, or a compromised spindle assembly checkpoint can lead to chromosome missegregation. However, how specific intrinsic features of the kinetochore—the critical chromosomal interface with spindle microtubules—impact chromosome segregation remains poorly understood. Here we used the unique cytological attributes of female Indian muntjac, the mammal with the lowest known chromosome number (2n = 6), to characterize and track individual chromosomes with distinct kinetochore size throughout mitosis. We show that centromere and kinetochore functional layers scale proportionally with centromere size. Measurement of intra-kinetochore distances, serial-section electron microscopy, and RNAi against key kinetochore proteins confirmed a standard structural and functional organization of the Indian muntjac kinetochores and revealed that microtubule binding capacity scales with kinetochore size. Surprisingly, we found that chromosome segregation in this species is not random. Chromosomes with larger kinetochores bi-oriented more efficiently and showed a 2-fold bias to congress to the equator in a motor-independent manner. Despite robust correction mechanisms during unperturbed mitosis, chromosomes with larger kinetochores were also strongly biased to establish erroneous merotelic attachments and missegregate during anaphase. This bias was impervious to the experimental attenuation of polar ejection forces on chromosome arms by RNAi against the chromokinesin Kif4a. Thus, kinetochore size is an important determinant of chromosome segregation fidelity. Centromere/kinetochore functional layers scale proportionally with centromere size Kinetochore microtubule binding capacity scales with kinetochore size Chromosome congression and bi-orientation are biased by kinetochore size Error formation leading to chromosome missegregation is biased by kinetochore size
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Affiliation(s)
- Danica Drpic
- Chromosome Instability & Dynamics Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Graduate Program in Areas of Basic and Applied Biology (GABBA), Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Ana C Almeida
- Chromosome Instability & Dynamics Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Paulo Aguiar
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto Nacional de Engenharia Biomédica (INEB), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Fioranna Renda
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Joana Damas
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK
| | - Harris A Lewin
- Department of Evolution and Ecology, University of California, Davis, Davis, CA 95616, USA
| | - Denis M Larkin
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK
| | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA; Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Helder Maiato
- Chromosome Instability & Dynamics Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Cell Division Group, Experimental Biology Unit, Department of Biomedicine, Faculdade de Medicina, Universidade do Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal.
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11
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Zedek F, Bureš P. Holocentric chromosomes: from tolerance to fragmentation to colonization of the land. ANNALS OF BOTANY 2018; 121:9-16. [PMID: 29069342 PMCID: PMC5786251 DOI: 10.1093/aob/mcx118] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 08/24/2017] [Indexed: 05/05/2023]
Abstract
BACKGROUND The dispersed occurrence of holocentric chromosomes across eukaryotes implies they are adaptive, but the conditions under which they confer an advantage over monocentric chromosomes remain unclear. Due to their extended kinetochore and the attachment of spindle microtubules along their entire length, holocentric chromosomes tolerate fragmentation; hence, they may be advantageous in times of exposure to factors that cause chromosomal fragmentation (clastogens). SCOPE It is shown that holocentric organisms may, indeed, thrive better than monocentric organisms under clastogenic conditions and that such conditions of various duration and intensity have occurred many times throughout the history of Earth's biota. One of the most important clastogenic events in eukaryotic history, in which holocentric chromosomes may have played the key role, was the colonization of land by plants and animals half a billion years ago. In addition to arguments supporting the anticlastogenic hypothesis of holocentric chromosomes and a discussion of its evolutionary consequences, experiments and analyses are proposed to explore this hypothesis in more depth. CONCLUSIONS It is argued that the tolerance to clastogens explains the origin of holocentric lineages and may also have far-reaching consequences for eukaryotic evolution in general as exemplified by the potential role of holocentric chromosomes in terrestrialization.
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Affiliation(s)
- František Zedek
- Department of Botany and Zoology, Masaryk University, Kotlarska, Brno, Czech Republic
- For correspondence. E-mail
| | - Petr Bureš
- Department of Botany and Zoology, Masaryk University, Kotlarska, Brno, Czech Republic
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12
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An SMC-like protein binds and regulates Caenorhabditis elegans condensins. PLoS Genet 2017; 13:e1006614. [PMID: 28301465 PMCID: PMC5373644 DOI: 10.1371/journal.pgen.1006614] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 03/30/2017] [Accepted: 02/01/2017] [Indexed: 01/17/2023] Open
Abstract
Structural Maintenance of Chromosomes (SMC) family proteins participate in multisubunit complexes that govern chromosome structure and dynamics. SMC-containing condensin complexes create chromosome topologies essential for mitosis/meiosis, gene expression, recombination, and repair. Many eukaryotes have two condensin complexes (I and II); C. elegans has three (I, II, and the X-chromosome specialized condensin IDC) and their regulation is poorly understood. Here we identify a novel SMC-like protein, SMCL-1, that binds to C. elegans condensin SMC subunits, and modulates condensin functions. Consistent with a possible role as a negative regulator, loss of SMCL-1 partially rescued the lethal and sterile phenotypes of a hypomorphic condensin mutant, while over-expression of SMCL-1 caused lethality, chromosome mis-segregation, and disruption of condensin IDC localization on X chromosomes. Unlike canonical SMC proteins, SMCL-1 lacks hinge and coil domains, and its ATPase domain lacks conserved amino acids required for ATP hydrolysis, leading to the speculation that it may inhibit condensin ATPase activity. SMCL-1 homologs are apparent only in the subset of Caenorhabditis species in which the condensin I and II subunit SMC-4 duplicated to create the condensin IDC- specific subunit DPY-27, suggesting that SMCL-1 helps this lineage cope with the regulatory challenges imposed by evolution of a third condensin complex. Our findings uncover a new regulator of condensins and highlight how the duplication and divergence of SMC complex components in various lineages has created new proteins with diverse functions in chromosome dynamics.
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13
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Barnhart-Dailey MC, Trivedi P, Stukenberg PT, Foltz DR. HJURP interaction with the condensin II complex during G1 promotes CENP-A deposition. Mol Biol Cell 2016; 28:54-64. [PMID: 27807043 PMCID: PMC5221629 DOI: 10.1091/mbc.e15-12-0843] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 10/17/2016] [Accepted: 10/26/2016] [Indexed: 01/27/2023] Open
Abstract
Condensin II interacts with human CENP-A chaperone HJURP and is present at centromeres in early G1. Condensin II, but not condensin I, is required for efficient CENP-A deposition in human cells. HJURP-induced chromatin decondensation at de novo centromeres is counteracted by the activity of condensin II. Centromeric chromatin is required for kinetochore assembly during mitosis and accurate chromosome segregation. A unique nucleosome containing the histone H3–specific variant CENP-A is the defining feature of centromeric chromatin. In humans, CENP-A nucleosome deposition occurs in early G1 just after mitotic exit at the time when the CENP-A deposition machinery localizes to centromeres. The mechanism by which CENP-A is deposited onto an existing, condensed chromatin template is not understood. Here we identify the selective association of the CENP-A chaperone HJURP with the condensin II complex and not condensin I. We show CAPH2 is present at centromeres during early G1 at the time when CENP-A deposition is occurring. CAPH2 localization to early G1 centromeres is dependent on HJURP. The CENP-A chaperone and assembly factor HJURP induces decondensation of a noncentromeric LacO array, and this decondensation is modulated by the condensin II complex. We show that condensin II function at the centromere is required for new CENP-A deposition in human cells. These data demonstrate that HJURP selectively recruits the condensin II chromatin-remodeling complex to facilitate CENP-A deposition in human cells.
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Affiliation(s)
- Meghan C Barnhart-Dailey
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical School, Charlottesville, VA 22908
| | - Prasad Trivedi
- Department of Cell Biology, University of Virginia Medical School, Charlottesville, VA 22908
| | - P Todd Stukenberg
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical School, Charlottesville, VA 22908.,Department of Cell Biology, University of Virginia Medical School, Charlottesville, VA 22908
| | - Daniel R Foltz
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical School, Charlottesville, VA 22908 .,Department of Cell Biology, University of Virginia Medical School, Charlottesville, VA 22908.,Department of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
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Zedek F, Veselý P, Horová L, Bureš P. Flow cytometry may allow microscope-independent detection of holocentric chromosomes in plants. Sci Rep 2016; 6:27161. [PMID: 27255216 PMCID: PMC4891681 DOI: 10.1038/srep27161] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 05/13/2016] [Indexed: 01/03/2023] Open
Abstract
Two chromosomal structures, known as monocentric and holocentric chromosomes, have evolved in eukaryotes. Acentric fragments of monocentric chromosomes are unequally distributed to daughter cells and/or lost, while holocentric fragments are inherited normally. In monocentric species, unequal distribution should generate chimeras of cells with different nuclear DNA content. We investigated whether such differences in monocentric species are detectable by flow cytometry (FCM) as (i) a decreased nuclear DNA content and (ii) an increased coefficient of variance (CV) of the G1 peak after gamma radiation-induced fragmentation. We compared 13 monocentric and 9 holocentric plant species. Unexpectedly, monocentrics and holocentrics did not differ with respect to parameters (i) and (ii) in their response to gamma irradiation. However, we found that the proportion of G2 nuclei was highly elevated in monocentrics after irradiation, while holocentrics were negligibly affected. Therefore, we hypothesize that DNA-damaging agents induce cell cycle arrest leading to endopolyploidy only in monocentric and not (or to much lesser extent) in holocentric plants. While current microscope-dependent methods for holocentrism detection are unreliable for small and numerous chromosomes, which are common in holocentrics, FCM can use somatic nuclei. Thus, FCM may be a rapid and reliable method of high-throughput screening for holocentric candidates across plant phylogeny.
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Affiliation(s)
- František Zedek
- Department of Botany and Zoology, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic
| | - Pavel Veselý
- Department of Botany and Zoology, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic
| | - Lucie Horová
- Department of Botany and Zoology, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic
| | - Petr Bureš
- Department of Botany and Zoology, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic
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15
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Hong Y, Sonneville R, Agostinho A, Meier B, Wang B, Blow JJ, Gartner A. The SMC-5/6 Complex and the HIM-6 (BLM) Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis. PLoS Genet 2016; 12:e1005872. [PMID: 27010650 PMCID: PMC4807058 DOI: 10.1371/journal.pgen.1005872] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 01/25/2016] [Indexed: 11/19/2022] Open
Abstract
Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs) to generate crossovers (COs) during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC) family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM) during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.
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Affiliation(s)
- Ye Hong
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - Remi Sonneville
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - Ana Agostinho
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - Bettina Meier
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - Bin Wang
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - J. Julian Blow
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - Anton Gartner
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
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16
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Rausch M, Ecsedi M, Bartake H, Müllner A, Grosshans H. A genetic interactome of the let-7 microRNA in C. elegans. Dev Biol 2015; 401:276-86. [PMID: 25732775 DOI: 10.1016/j.ydbio.2015.02.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/13/2015] [Accepted: 02/17/2015] [Indexed: 02/08/2023]
Abstract
The heterochronic pathway controls temporal patterning during Caenorhabditis elegans larval development. The highly conserved let-7 microRNA (miRNA) plays a key role in this pathway, directing the larval-to-adult (L/A) transition. Hence, knowledge of the genetic interactome of let-7 has the potential to provide insight into both control of temporal cell fates and mechanisms of regulation and function of miRNAs. Here, we report the results of a genome-wide, RNAi-based screen for suppressors of let-7 mutant vulval bursting. The 201 genetic interaction partners of let-7 thus identified include genes that promote target silencing activity of let-7, seam cell differentiation, or both. We illustrate the suitability of our approach by uncovering the mitotic cyclin-dependent kinase CDK-1 as a downstream effector of let-7 that affects both seam cell proliferation and differentiation, and by identifying a core set of candidate modulators of let-7 activity, which includes all subunits of the condensin II complex. We propose that the genes identified in our screen thus constitute a valuable resource for studies of the heterochronic pathway and miRNAs.
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Affiliation(s)
- Magdalene Rausch
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; University of Basel, Petersplatz 1, CH-4003 Basel, Switzerland
| | - Matyas Ecsedi
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; University of Basel, Petersplatz 1, CH-4003 Basel, Switzerland
| | - Hrishikesh Bartake
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; University of Basel, Petersplatz 1, CH-4003 Basel, Switzerland
| | - Almuth Müllner
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | - Helge Grosshans
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.
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17
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Lau AC, Nabeshima K, Csankovszki G. The C. elegans dosage compensation complex mediates interphase X chromosome compaction. Epigenetics Chromatin 2014; 7:31. [PMID: 25400696 PMCID: PMC4232692 DOI: 10.1186/1756-8935-7-31] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/06/2014] [Indexed: 12/04/2022] Open
Abstract
Background Dosage compensation is a specialized gene regulatory mechanism which equalizes X-linked gene expression between sexes. In Caenorhabditis elegans, dosage compensation is achieved by the activity of the dosage compensation complex (DCC). The DCC localizes to both X chromosomes in hermaphrodites to downregulate gene expression by half. The DCC contains a subcomplex (condensin IDC) similar to the evolutionarily conserved condensin complexes which play fundamental roles in chromosome dynamics during mitosis and meiosis. Therefore, mechanisms related to mitotic chromosome condensation have been long hypothesized to mediate dosage compensation. However experimental evidence was lacking. Results Using 3D FISH microscopy to measure the volumes of X and chromosome I territories and to measure distances between individual loci, we show that hermaphrodite worms deficient in DCC proteins have enlarged interphase X chromosomes when compared to wild type. By contrast, chromosome I is unaffected. Interestingly, hermaphrodite worms depleted of condensin I or II show no phenotype. Therefore X chromosome compaction is specific to condensin IDC. In addition, we show that SET-1, SET-4, and SIR-2.1, histone modifiers whose activity is regulated by the DCC, need to be present for the compaction of the X chromosome territory. Conclusion These results support the idea that condensin IDC, and the histone modifications regulated by the DCC, mediate interphase X chromosome compaction. Our results link condensin-mediated chromosome compaction, an activity connected to mitotic chromosome condensation, to chromosome-wide repression of gene expression in interphase. Electronic supplementary material The online version of this article (doi:10.1186/1756-8935-7-31) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alyssa C Lau
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109 Michigan
| | - Kentaro Nabeshima
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109 Michigan
| | - Györgyi Csankovszki
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109 Michigan
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18
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Smith SJ, Osman K, Franklin FCH. The condensin complexes play distinct roles to ensure normal chromosome morphogenesis during meiotic division in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 80:255-68. [PMID: 25065716 PMCID: PMC4552968 DOI: 10.1111/tpj.12628] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 07/11/2014] [Accepted: 07/23/2014] [Indexed: 05/03/2023]
Abstract
Meiosis is a specialized cell division essential for sexual reproduction. During meiosis the chromosomes are highly organized, and correct chromosome architecture is required for faithful segregation of chromosomes at anaphase I and II. Condensin is involved in chromosome organization during meiotic and mitotic cell divisions. Three condensin subunits, AtSMC4 and the condensin I and II specific subunits AtCAP-D2 and AtCAP-D3, respectively, have been studied for their role in meiosis. This has revealed that both the condensin I and condensin II complexes are required to maintain normal structural integrity of the meiotic chromosomes during the two nuclear divisions. Their roles appear functionally distinct in that condensin I is required to maintain normal compaction of the centromeric repeats and 45S rDNA, whereas loss of condensin II was associated with extensive interchromosome connections at metaphase I. Depletion of condensin is also associated with a slight reduction in crossover formation, suggesting a role during meiotic prophase I.
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Affiliation(s)
- Sarah J Smith
- School of Biosciences, University of BirminghamEdgbaston, Birmingham, B15 2TT, UK
- School of Biological and Biomedical Sciences, Durham UniversitySouth Road, Durham, DH1 3LE, UK
| | - Kim Osman
- School of Biosciences, University of BirminghamEdgbaston, Birmingham, B15 2TT, UK
| | - F Christopher H Franklin
- School of Biosciences, University of BirminghamEdgbaston, Birmingham, B15 2TT, UK
- *For correspondence (e-mail )
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19
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Kranz AL, Jiao CY, Winterkorn LH, Albritton SE, Kramer M, Ercan S. Genome-wide analysis of condensin binding in Caenorhabditis elegans. Genome Biol 2014; 14:R112. [PMID: 24125077 PMCID: PMC3983662 DOI: 10.1186/gb-2013-14-10-r112] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 10/14/2013] [Indexed: 11/26/2022] Open
Abstract
Background Condensins are multi-subunit protein complexes that are essential for chromosome condensation during mitosis and meiosis, and play key roles in transcription regulation during interphase. Metazoans contain two condensins, I and II, which perform different functions and localize to different chromosomal regions. Caenorhabditis elegans contains a third condensin, IDC, that is targeted to and represses transcription of the X chromosome for dosage compensation. Results To understand condensin binding and function, we performed ChIP-seq analysis of C. elegans condensins in mixed developmental stage embryos, which contain predominantly interphase nuclei. Condensins bind to a subset of active promoters, tRNA genes and putative enhancers. Expression analysis in kle-2-mutant larvae suggests that the primary effect of condensin II on transcription is repression. A DNA sequence motif, GCGC, is enriched at condensin II binding sites. A sequence extension of this core motif, AGGG, creates the condensin IDC motif. In addition to differences in recruitment that result in X-enrichment of condensin IDC and condensin II binding to all chromosomes, we provide evidence for a shared recruitment mechanism, as condensin IDC recruiter SDC-2 also recruits condensin II to the condensin IDC recruitment sites on the X. In addition, we found that condensin sites overlap extensively with the cohesin loader SCC-2, and that SDC-2 also recruits SCC-2 to the condensin IDC recruitment sites. Conclusions Our results provide the first genome-wide view of metazoan condensin II binding in interphase, define putative recruitment motifs, and illustrate shared loading mechanisms for condensin IDC and condensin II.
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20
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Kim JH, Shim J, Ji MJ, Jung Y, Bong SM, Jang YJ, Yoon EK, Lee SJ, Kim KG, Kim YH, Lee C, Lee BI, Kim KT. The condensin component NCAPG2 regulates microtubule-kinetochore attachment through recruitment of Polo-like kinase 1 to kinetochores. Nat Commun 2014; 5:4588. [PMID: 25109385 DOI: 10.1038/ncomms5588] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 07/03/2014] [Indexed: 12/21/2022] Open
Abstract
The early event of microtubule-kinetochore attachment is a critical stage for precise chromosome segregation. Here we report that NCAPG2, which is a component of the condensin II complex, mediates chromosome segregation through microtubule-kinetochore attachment by recruiting PLK1 to prometaphase kinetochores. NCAPG2 colocalizes with PLK1 at prometaphase kinetochores and directly interacts with the polo-box domain (PBD) of PLK1 via its highly conserved C-terminal region. In both humans and Caenorhabditis elegans, when NCAPG2 is depleted, the attachment of the spindle to the kinetochore is loosened and misoriented. This is caused by the disruption of PLK1 localization to the kinetochore and by the decreased phosphorylation of its kinetochore substrate, BubR1. In addition, the crystal structure of the PBD of PLK1, in complex with the C-terminal region of NCAPG2, (1007)VLS-pT-L(1011), exhibits structural conservation of PBD-phosphopeptides, suggesting that the regulation of NCAPG2 function is phosphorylation-dependent. These findings suggest that NCAPG2 plays an important role in regulating proper chromosome segregation through a functional interaction with PLK1 during mitosis.
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Affiliation(s)
- Jae Hyeong Kim
- 1] Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea [2]
| | - Jaegal Shim
- 1] Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea [2]
| | - Min-Ju Ji
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Yuna Jung
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Seoung Min Bong
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Young-Joo Jang
- Laboratory of Cell Cycle and Signal Transduction, Department of Nanobiomedical Science and BK21 PLUS Research Center for Regenerative Medicine, Dankook University, Cheonan, Chungnam 330-714, Republic of Korea
| | - Eun-Kyung Yoon
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Sang-Jin Lee
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Kwang Gi Kim
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Yon Hui Kim
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Changwoo Lee
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi 440-746, Republic of Korea
| | - Byung Il Lee
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
| | - Kyung-Tae Kim
- Research Institute, National Cancer Center, Goyang, Gyeonggi 410-769, Republic of Korea
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Bureš P, Zedek F. Holokinetic drive: centromere drive in chromosomes without centromeres. Evolution 2014; 68:2412-20. [PMID: 24758327 DOI: 10.1111/evo.12437] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 04/13/2014] [Indexed: 02/02/2023]
Abstract
Similar to how the model of centromere drive explains the size and complexity of centromeres in monocentrics (organisms with localized centromeres), our model of holokinetic drive is consistent with the divergent evolution of chromosomal size and number in holocentrics (organisms with nonlocalized centromeres) exhibiting holokinetic meiosis (holokinetics). Holokinetic drive is proposed to facilitate chromosomal fission and/or repetitive DNA removal (or any segmental deletion) when smaller homologous chromosomes are preferentially inherited or chromosomal fusion and/or repetitive DNA proliferation (or any segmental duplication) when larger homologs are preferred. The hypothesis of holokinetic drive is supported primarily by the negative correlation between chromosome number and genome size that is documented in holokinetic lineages. The supporting value of two older cross-experiments on holokinetic structural heterozygotes (the rush Luzula elegans and butterflies of the genus Antheraea) that indicate the presence of size-preferential homolog transmission via female meiosis for holokinetic drive is discussed, along with the further potential consequences of holokinetic drive in comparison with centromere drive.
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Affiliation(s)
- Petr Bureš
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Brno, Czech Republic.
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22
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Fujiwara T, Tanaka K, Kuroiwa T, Hirano T. Spatiotemporal dynamics of condensins I and II: evolutionary insights from the primitive red alga Cyanidioschyzon merolae. Mol Biol Cell 2013; 24:2515-27. [PMID: 23783031 PMCID: PMC3744952 DOI: 10.1091/mbc.e13-04-0208] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Spatiotemporal dynamics of condensins I and II in the primitive red alga Cyanidioschyzon merolae is surprisingly similar to that observed in mammalian cells. Condensin II is not essential for mitosis under laboratory growth conditions but is required for sister centromere resolution in the presence of a microtubule drug. Condensins are multisubunit complexes that play central roles in chromosome organization and segregation in eukaryotes. Many eukaryotic species have two different condensin complexes (condensins I and II), although some species, such as fungi, have condensin I only. Here we use the red alga Cyanidioschyzon merolae as a model organism because it represents the smallest and simplest organism that is predicted to possess both condensins I and II. We demonstrate that, despite the great evolutionary distance, spatiotemporal dynamics of condensins in C. merolae is strikingly similar to that observed in mammalian cells: condensin II is nuclear throughout the cell cycle, whereas condensin I appears on chromosomes only after the nuclear envelope partially dissolves at prometaphase. Unlike in mammalian cells, however, condensin II is confined to centromeres in metaphase, whereas condensin I distributes more broadly along arms. We firmly establish a targeted gene disruption technique in this organism and find, to our surprise, that condensin II is not essential for mitosis under laboratory growth conditions, although it plays a crucial role in facilitating sister centromere resolution in the presence of a microtubule drug. The results provide fundamental insights into the evolution of condensin-based chromosome architecture and dynamics.
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Affiliation(s)
- Takayuki Fujiwara
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
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Chavez SL, Loewke KE, Han J, Moussavi F, Colls P, Munne S, Behr B, Reijo Pera RA. Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage. Nat Commun 2013; 3:1251. [PMID: 23212380 PMCID: PMC3535341 DOI: 10.1038/ncomms2249] [Citation(s) in RCA: 195] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 11/01/2012] [Indexed: 11/09/2022] Open
Abstract
Previous studies have demonstrated that aneuploidy in human embryos is surprisingly frequent with 50–80% of cleavage-stage human embryos carrying an abnormal chromosome number. Here we combine non-invasive time-lapse imaging with karyotypic reconstruction of all blastomeres in four-cell human embryos to address the hypothesis that blastomere behaviour may reflect ploidy during the first two cleavage divisions. We demonstrate that precise cell cycle parameter timing is observed in all euploid embryos to the four-cell stage, whereas only 30% of aneuploid embryos exhibit parameter values within normal timing windows. Further, we observe that the generation of human embryonic aneuploidy is complex with contribution from chromosome-containing fragments/micronuclei that frequently emerge and may persist or become reabsorbed during interphase. These findings suggest that cell cycle and fragmentation parameters of individual blastomeres are diagnostic of ploidy, amenable to automated tracking algorithms, and likely of clinical relevance in reducing transfer of embryos prone to miscarriage. Abnormal human embryo development is implicated in the embryo arrest observed during in vitro fertilization. Chavez and colleagues perform time-lapse imaging on human embryos and find that chromosomally abnormal embryos exhibit diverse cell cycle parameters that may contribute to arrest.
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Affiliation(s)
- Shawn L Chavez
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, California 94305, USA
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Bembenek JN, Verbrugghe KJC, Khanikar J, Csankovszki G, Chan RC. Condensin and the spindle midzone prevent cytokinesis failure induced by chromatin bridges in C. elegans embryos. Curr Biol 2013; 23:937-46. [PMID: 23684975 DOI: 10.1016/j.cub.2013.04.028] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 03/12/2013] [Accepted: 04/09/2013] [Indexed: 11/28/2022]
Abstract
BACKGROUND During cell division, chromosomes must clear the path of the cleavage furrow before the onset of cytokinesis. The abscission checkpoint in mammalian cells stabilizes the cleavage furrow in the presence of a chromatin obstruction. This provides time to resolve the obstruction before the cleavage furrow regresses or breaks the chromosomes, preventing aneuploidy or DNA damage. Two unanswered questions in the proposed mechanistic pathway of the abscission checkpoint concern factors involved in (1) resolving the obstructions and (2) coordinating obstruction resolution with the delay in cytokinesis. RESULTS We found that the one-cell and two-cell C. elegans embryos suppress furrow regression following depletion of essential chromosome-segregation factors: topoisomerase II(TOP-2), CENP-A(HCP-3), cohesin, and to a lesser degree, condensin. Chromatin obstructions activated Aurora B(AIR-2) at the spindle midzone, which is needed for the abscission checkpoint in other systems. Condensin I, but not condensin II, localizes to the spindle midzone in anaphase and to the midbody during normal cytokinesis. Interestingly, condensin I is enriched on chromatin bridges and near the midzone/midbody in an AIR-2-dependent manner. Disruption of AIR-2, the spindle midzone, or condensin leads to cytokinesis failure in a chromatin-obstruction-dependent manner. Examination of the condensin-deficient embryos uncovered defects in both the resolution of the chromatin obstructions and the maintenance of the stable cleavage furrow. CONCLUSIONS We postulate that condensin I is recruited by Aurora B(AIR-2) to aid in the resolution of chromatin obstructions and also helps generate a signal to maintain the delay in cytokinesis.
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Affiliation(s)
- Joshua N Bembenek
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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Herzog S, Nagarkar Jaiswal S, Urban E, Riemer A, Fischer S, Heidmann SK. Functional dissection of the Drosophila melanogaster condensin subunit Cap-G reveals its exclusive association with condensin I. PLoS Genet 2013; 9:e1003463. [PMID: 23637630 PMCID: PMC3630105 DOI: 10.1371/journal.pgen.1003463] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 03/05/2013] [Indexed: 11/19/2022] Open
Abstract
The heteropentameric condensin complexes have been shown to participate in mitotic chromosome condensation and to be required for unperturbed chromatid segregation in nuclear divisions. Vertebrates have two condensin complexes, condensin I and condensin II, which contain the same structural maintenance of chromosomes (SMC) subunits SMC2 and SMC4, but differ in their composition of non-SMC subunits. While a clear biochemical and functional distinction between condensin I and condensin II has been established in vertebrates, the situation in Drosophila melanogaster is less defined. Since Drosophila lacks a clear homolog for the condensin II-specific subunit Cap-G2, the condensin I subunit Cap-G has been hypothesized to be part of both complexes. In vivo microscopy revealed that a functional Cap-G-EGFP variant shows a distinct nuclear enrichment during interphase, which is reminiscent of condensin II localization in vertebrates and contrasts with the cytoplasmic enrichment observed for the other EGFP-fused condensin I subunits. However, we show that this nuclear localization is dispensable for Cap-G chromatin association, for its assembly into the condensin I complex and, importantly, for development into a viable and fertile adult animal. Immunoprecipitation analyses and complex formation studies provide evidence that Cap-G does not associate with condensin II-specific subunits, while it can be readily detected in complexes with condensin I-specific proteins in vitro and in vivo. Mass-spectrometric analyses of proteins associated with the condensin II-specific subunit Cap-H2 not only fail to identify Cap-G but also the other known condensin II-specific homolog Cap-D3. As condensin II-specific subunits are also not found associated with SMC2, our results question the existence of a soluble condensin II complex in Drosophila.
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Affiliation(s)
- Sabine Herzog
- Lehrstuhl für Genetik, University of Bayreuth, Bayreuth, Germany
| | | | - Evelin Urban
- Lehrstuhl für Genetik, University of Bayreuth, Bayreuth, Germany
| | - Anna Riemer
- Lehrstuhl für Genetik, University of Bayreuth, Bayreuth, Germany
| | - Sina Fischer
- Lehrstuhl für Genetik, University of Bayreuth, Bayreuth, Germany
- Lehrstuhl für Pflanzenphysiologie, University of Bayreuth, Bayreuth, Germany
| | - Stefan K. Heidmann
- Lehrstuhl für Genetik, University of Bayreuth, Bayreuth, Germany
- * E-mail:
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26
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Abstract
Condensins are multisubunit protein complexes that play a fundamental role in the structural and functional organization of chromosomes in the three domains of life. Most eukaryotic species have two different types of condensin complexes, known as condensins I and II, that fulfill nonoverlapping functions and are subjected to differential regulation during mitosis and meiosis. Recent studies revealed that the two complexes contribute to a wide variety of interphase chromosome functions, such as gene regulation, recombination, and repair. Also emerging are their cell type- and tissue-specific functions and relevance to human disease. Biochemical and structural analyses of eukaryotic and bacterial condensins steadily uncover the mechanisms of action of this class of highly sophisticated molecular machines. Future studies on condensins will not only enhance our understanding of chromosome architecture and dynamics, but also help address a previously underappreciated yet profound set of questions in chromosome biology.
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Affiliation(s)
- Tatsuya Hirano
- Chromosome Dynamics Laboratory, RIKEN Advanced Science Institute, Wako, Saitama, Japan.
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27
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Green LC, Kalitsis P, Chang TM, Cipetic M, Kim JH, Marshall O, Turnbull L, Whitchurch CB, Vagnarelli P, Samejima K, Earnshaw WC, Choo KHA, Hudson DF. Contrasting roles of condensin I and condensin II in mitotic chromosome formation. J Cell Sci 2012; 125:1591-604. [PMID: 22344259 DOI: 10.1242/jcs.097790] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In vertebrates, two condensin complexes exist, condensin I and condensin II, which have differing but unresolved roles in organizing mitotic chromosomes. To dissect accurately the role of each complex in mitosis, we have made and studied the first vertebrate conditional knockouts of the genes encoding condensin I subunit CAP-H and condensin II subunit CAP-D3 in chicken DT40 cells. Live-cell imaging reveals highly distinct segregation defects. CAP-D3 (condensin II) knockout results in masses of chromatin-containing anaphase bridges. CAP-H (condensin I)-knockout anaphases have a more subtle defect, with chromatids showing fine chromatin fibres that are associated with failure of cytokinesis and cell death. Super-resolution microscopy reveals that condensin-I-depleted mitotic chromosomes are wider and shorter, with a diffuse chromosome scaffold, whereas condensin-II-depleted chromosomes retain a more defined scaffold, with chromosomes more stretched and seemingly lacking in axial rigidity. We conclude that condensin II is required primarily to provide rigidity by establishing an initial chromosome axis around which condensin I can arrange loops of chromatin.
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Affiliation(s)
- Lydia C Green
- Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria 3052, Australia
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28
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Abstract
Caenorhabditis elegans is an important system for the study of cell cycle regulation in the context of animal development. One of the most powerful features of C. elegans is the invariant cell lineage in which somatic cells initiate cell division at specific times within the developmental program. The cell lineage is fully known and provides the foundation for the analysis of cell cycle progression at single-cell resolution in a multicellular organism. In this chapter, we describe the different types of cell cycles observed in C. elegans, and provide methods and reagents for the analysis of cell cycle progression as well as specific cell cycle phases. We also provide strategies for the analysis and proper interpretation of cell cycle and checkpoint mutants.
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29
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Silkworth WT, Nardi IK, Paul R, Mogilner A, Cimini D. Timing of centrosome separation is important for accurate chromosome segregation. Mol Biol Cell 2011; 23:401-11. [PMID: 22130796 PMCID: PMC3268720 DOI: 10.1091/mbc.e11-02-0095] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Spindle assembly, establishment of kinetochore attachment, and sister chromatid separation must occur during mitosis in a highly coordinated fashion to ensure accurate chromosome segregation. In most vertebrate cells, the nuclear envelope must break down to allow interaction between microtubules of the mitotic spindle and the kinetochores. It was previously shown that nuclear envelope breakdown (NEB) is not coordinated with centrosome separation and that centrosome separation can be either complete at the time of NEB or can be completed after NEB. In this study, we investigated whether the timing of centrosome separation affects subsequent mitotic events such as establishment of kinetochore attachment or chromosome segregation. We used a combination of experimental and computational approaches to investigate kinetochore attachment and chromosome segregation in cells with complete versus incomplete spindle pole separation at NEB. We found that cells with incomplete spindle pole separation exhibit higher rates of kinetochore misattachments and chromosome missegregation than cells that complete centrosome separation before NEB. Moreover, our mathematical model showed that two spindle poles in close proximity do not "search" the entire cellular space, leading to formation of large numbers of syntelic attachments, which can be an intermediate stage in the formation of merotelic kinetochores.
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30
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Yi Q, Zhao X, Huang Y, Ma T, Zhang Y, Hou H, Cooke HJ, Yang DQ, Wu M, Shi Q. p53 dependent centrosome clustering prevents multipolar mitosis in tetraploid cells. PLoS One 2011; 6:e27304. [PMID: 22076149 PMCID: PMC3208627 DOI: 10.1371/journal.pone.0027304] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 10/13/2011] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND p53 abnormality and aneuploidy often coexist in human tumors, and tetraploidy is considered as an intermediate between normal diploidy and aneuploidy. The purpose of this study was to investigate whether and how p53 influences the transformation from tetraploidy to aneuploidy. PRINCIPAL FINDINGS Live cell imaging was performed to determine the fates and mitotic behaviors of several human and mouse tetraploid cells with different p53 status, and centrosome and spindle immunostaining was used to investigate centrosome behaviors. We found that p53 dominant-negative mutation, point mutation, or knockout led to a 2∼ 33-fold increase of multipolar mitosis in N/TERT1, 3T3 and mouse embryonic fibroblasts (MEFs), while mitotic entry and cell death were not significantly affected. In p53-/- tetraploid MEFs, the ability of centrosome clustering was compromised, while centrosome inactivation was not affected. Suppression of RhoA/ROCK activity by specific inhibitors in p53-/- tetraploid MEFs enhanced centrosome clustering, decreased multipolar mitosis from 38% to 20% and 16% for RhoA and ROCK, respectively, while expression of constitutively active RhoA in p53+/+ tetraploid 3T3 cells increased the frequency of multipolar mitosis from 15% to 35%. CONCLUSIONS p53 could not prevent tetraploid cells entering mitosis or induce tetraploid cell death. However, p53 abnormality impaired centrosome clustering and lead to multipolar mitosis in tetraploid cells by modulating the RhoA/ROCK signaling pathway.
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Affiliation(s)
- Qiyi Yi
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Xiaoyu Zhao
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Yun Huang
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Tieliang Ma
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Yingyin Zhang
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Heli Hou
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Howard J. Cooke
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
- MRC Human Genetics Unit and Institute of Genetics and Molecular Medicine, Western General Hospital, Edinburgh, United Kingdom
| | - Da-Qing Yang
- Sanford Research/University of South Dakota, Sanford Health, Sioux Falls, South Dakota, United States of America
| | - Mian Wu
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Qinghua Shi
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
- * E-mail:
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31
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Collette KS, Petty EL, Golenberg N, Bembenek JN, Csankovszki G. Different roles for Aurora B in condensin targeting during mitosis and meiosis. J Cell Sci 2011; 124:3684-94. [PMID: 22025633 DOI: 10.1242/jcs.088336] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Condensin complexes are essential for mitotic and meiotic chromosome segregation. Caenorhabditis elegans, like other metazoans, has two distinct mitotic and meiotic condensin complexes (I and II), which occupy distinct chromosomal domains and perform non-redundant functions. Despite the differences in mitotic and meiotic chromosome behavior, we uncovered several conserved aspects of condensin targeting during these processes. During both mitosis and meiosis, condensin II loads onto chromosomes in early prophase, and condensin I loads at entry into prometaphase. During both mitosis and meiosis, the localization of condensin I, but not condensin II, closely parallels the localization of the chromosomal passenger kinase Aurora B (AIR-2 in C. elegans). Interestingly, condensin I and AIR-2 also colocalize on the spindle midzone during anaphase of mitosis, and between separating chromosomes during anaphase of meiosis. Consistently, AIR-2 affects the targeting of condensin I but not condensin II. However, the role AIR-2 plays in condensin I targeting during these processes is different. In mitosis, AIR-2 activity is required for chromosomal association of condensin I. By contrast, during meiosis, AIR-2 is not required for condensin I chromosomal association, but it provides cues for correct spatial targeting of the complex.
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Affiliation(s)
- Karishma S Collette
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
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32
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Abstract
To segregate chromosomes properly, the cell must prevent merotely, an error that occurs when a single kinetochore is attached to microtubules emanating from both spindle poles. Recent evidence suggests that cooperation between Pcs1/Mde4 and condensin complexes plays an important role in preventing merotely.
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33
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Merotelic kinetochore attachment: causes and effects. Trends Cell Biol 2011; 21:374-81. [PMID: 21306900 PMCID: PMC3117139 DOI: 10.1016/j.tcb.2011.01.003] [Citation(s) in RCA: 167] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 12/13/2010] [Accepted: 01/07/2011] [Indexed: 01/06/2023]
Abstract
Accurate chromosome segregation depends on the proper attachment of sister kinetochores to microtubules emanating from opposite spindle poles. Merotelic kinetochore orientation is an error in which a single kinetochore is attached to microtubules emanating from both spindle poles. Despite correction mechanisms, merotelically attached kinetochores can persist until anaphase, causing chromatids to lag on the mitotic spindle and hindering their timely segregation. Recent studies showing that merotelic kinetochore attachment represents a major mechanism of aneuploidy in mitotic cells and is the primary mechanism of chromosomal instability in cancer cells have underlined the importance of studying merotely. Here, we highlight recent progress in our understanding of how cells prevent and correct merotelic kinetochore attachments.
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34
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Caenorhabditis elegans cyclin B3 is required for multiple mitotic processes including alleviation of a spindle checkpoint-dependent block in anaphase chromosome segregation. PLoS Genet 2010; 6:e1001218. [PMID: 21124864 PMCID: PMC2991249 DOI: 10.1371/journal.pgen.1001218] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Accepted: 10/25/2010] [Indexed: 12/22/2022] Open
Abstract
The master regulators of the cell cycle are cyclin-dependent kinases (Cdks), which influence the function of a myriad of proteins via phosphorylation. Mitotic Cdk1 is activated by A-type, as well as B1- and B2-type, cyclins. However, the role of a third, conserved cyclin B family member, cyclin B3, is less well defined. Here, we show that Caenorhabditis elegans CYB-3 has essential and distinct functions from cyclin B1 and B2 in the early embryo. CYB-3 is required for the timely execution of a number of cell cycle events including completion of the MII meiotic division of the oocyte nucleus, pronuclear migration, centrosome maturation, mitotic chromosome condensation and congression, and, most strikingly, progression through the metaphase-to-anaphase transition. Our experiments reveal that the extended metaphase delay in CYB-3–depleted embryos is dependent on an intact spindle assembly checkpoint (SAC) and results in salient defects in the architecture of holocentric metaphase chromosomes. Furthermore, genetically increasing or decreasing dynein activity results in the respective suppression or enhancement of CYB-3–dependent defects in cell cycle progression. Altogether, these data reveal that CYB-3 plays a unique, essential role in the cell cycle including promoting mitotic dynein functionality and alleviation of a SAC–dependent block in anaphase chromosome segregation. Every time a cell divides in two, the genetic material, DNA, is copied; each copied chromosome is referred to as a pair of sister chromatids. Each chromatid must be cleanly separated from its sister so that each daughter cell inherits the same DNA complement as the starting cell. The mitotic spindle is a cellular machine that physically separates the sister chromatids from one another. The chromatids are attached to the spindle at kinetochores, which are structures built at specific sites (centromeres) on each chromatid. The cell monitors the attachment of each chromatid and blocks their separation until they are all properly attached. This process is called the spindle assembly checkpoint (SAC). Here we report that loss of an evolutionarily conserved cell cycle regulator, Cyclin B3/CYB-3, results in an unusual and strikingly persistent SAC–dependent delay in sister chromatid separation. Furthermore, CYB-3 promotes the activity of a cellular motor, dynein, in this and other mitotic processes. Altogether, our results indicate that Cyclin B3 genetically interacts with mitotic dynein and is absolutely required to satisfy a SAC–dependent inhibition in sister chromatid separation.
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35
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Abstract
Dosage compensation in the nematode Caenorhabditis elegans is achieved by the binding of a condensin-like dosage compensation complex (DCC) to both X chromosomes in hermaphrodites to downregulate gene expression two-fold. Condensin I(DC), a sub-part of the DCC, differs from the mitotic condensin I complex by a single subunit, strengthening the connection between dosage compensation and mitotic chromosome condensation. The DCC is targeted to X chromosomes by initial binding to a number of recruiting elements, followed by dispersal or spreading to secondary sites. While the complex is greatly enriched on the X chromosomes, many sites on autosomes also bind the complex. DCC binding does not correlate with DCC-mediated repression, suggesting that the complex acts in a chromosome-wide manner, rather than on a gene-by-gene basis. Worm dosage compensation represents an excellent model system to study how condensin-mediated changes in higher order chromatin organization affect gene expression.
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36
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van Wolfswinkel JC, Claycomb JM, Batista PJ, Mello CC, Berezikov E, Ketting RF. CDE-1 affects chromosome segregation through uridylation of CSR-1-bound siRNAs. Cell 2009; 139:135-48. [PMID: 19804759 DOI: 10.1016/j.cell.2009.09.012] [Citation(s) in RCA: 142] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Revised: 07/01/2009] [Accepted: 09/11/2009] [Indexed: 01/22/2023]
Abstract
We have studied the function of a conserved germline-specific nucleotidyltransferase protein, CDE-1, in RNAi and chromosome segregation in C. elegans. CDE-1 localizes specifically to mitotic chromosomes in embryos. This localization requires the RdRP EGO-1, which physically interacts with CDE-1, and the Argonaute protein CSR-1. We found that CDE-1 is required for the uridylation of CSR-1 bound siRNAs, and that in the absence of CDE-1 these siRNAs accumulate to inappropriate levels, accompanied by defects in both meiotic and mitotic chromosome segregation. Elevated siRNA levels are associated with erroneous gene silencing, most likely through the inappropriate loading of CSR-1 siRNAs into other Argonaute proteins. We propose a model in which CDE-1 restricts specific EGO-1-generated siRNAs to the CSR-1 mediated, chromosome associated RNAi pathway, thus separating it from other endogenous RNAi pathways. The conserved nature of CDE-1 suggests that similar sorting mechanisms may operate in other animals, including mammals.
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Affiliation(s)
- Josien C van Wolfswinkel
- Hubrecht Institute-KNAW and University Medical Centre Utrecht, Uppsalalaan 8, Utrecht, The Netherlands
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37
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Human condensin function is essential for centromeric chromatin assembly and proper sister kinetochore orientation. PLoS One 2009; 4:e6831. [PMID: 19714251 PMCID: PMC2730017 DOI: 10.1371/journal.pone.0006831] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Accepted: 08/03/2009] [Indexed: 12/25/2022] Open
Abstract
Condensins I and II in vertebrates are essential ATP-dependent complexes necessary for chromosome condensation in mitosis. Condensins depletion is known to perturb structure and function of centromeres, however the mechanism of this functional link remains elusive. Depletion of condensin activity is now shown to result in a significant loss of loading of CENP-A, the histone H3 variant found at active centromeres and the proposed epigenetic mark of centromere identity. Absence of condensins and/or CENP-A insufficiency produced a specific kinetochore defect, such that a functional mitotic checkpoint cannot prevent chromosome missegregation resulting from improper attachment of sister kinetochores to spindle microtubules. Spindle microtubule-dependent deformation of both inner kinetochores and the HEC1/Ndc80 microtubule-capturing module, then results in kinetochore separation from the Aurora B pool and ensuing reduced kinase activity at centromeres. Moreover, recovery from mitosis-inhibition by monastrol revealed a high incidence of merotelic attachment that was nearly identical with condensin depletion, Aurora B inactivation, or both, indicating that the Aurora B dysfunction is the key defect leading to chromosome missegregation in condensin-depleted cells. Thus, beyond a requirement for global chromosome condensation, condensins play a pivotal role in centromere assembly, proper spatial positioning of microtubule-capturing modules and positioning complexes of the inner centromere versus kinetochore plates.
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38
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Csankovszki G, Collette K, Spahl K, Carey J, Snyder M, Petty E, Patel U, Tabuchi T, Liu H, McLeod I, Thompson J, Sarkeshik A, Sarkesik A, Yates J, Meyer BJ, Hagstrom K. Three distinct condensin complexes control C. elegans chromosome dynamics. Curr Biol 2009; 19:9-19. [PMID: 19119011 DOI: 10.1016/j.cub.2008.12.006] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 12/02/2008] [Accepted: 12/04/2008] [Indexed: 10/21/2022]
Abstract
BACKGROUND Condensin complexes organize chromosome structure and facilitate chromosome segregation. Higher eukaryotes have two complexes, condensin I and condensin II, each essential for chromosome segregation. The nematode Caenorhabditis elegans was considered an exception, because it has a mitotic condensin II complex but appeared to lack mitotic condensin I. Instead, its condensin I-like complex (here called condensin I(DC)) dampens gene expression along hermaphrodite X chromosomes during dosage compensation. RESULTS Here we report the discovery of a third condensin complex, condensin I, in C. elegans. We identify new condensin subunits and show that each complex has a conserved five-subunit composition. Condensin I differs from condensin I(DC) by only a single subunit. Yet condensin I binds to autosomes and X chromosomes in both sexes to promote chromosome segregation, whereas condensin I(DC) binds specifically to X chromosomes in hermaphrodites to regulate transcript levels. Both condensin I and II promote chromosome segregation, but associate with different chromosomal regions during mitosis and meiosis. Unexpectedly, condensin I also localizes to regions of cohesion between meiotic chromosomes before their segregation. CONCLUSIONS We demonstrate that condensin subunits in C. elegans form three complexes, one that functions in dosage compensation and two that function in mitosis and meiosis. These results highlight how the duplication and divergence of condensin subunits during evolution may facilitate their adaptation to specialized chromosomal roles and illustrate the versatility of condensins to function in both gene regulation and chromosome segregation.
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Affiliation(s)
- Gyorgyi Csankovszki
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
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39
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Cimini D. Merotelic kinetochore orientation, aneuploidy, and cancer. Biochim Biophys Acta Rev Cancer 2008; 1786:32-40. [PMID: 18549824 DOI: 10.1016/j.bbcan.2008.05.003] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 04/21/2008] [Accepted: 05/13/2008] [Indexed: 01/16/2023]
Abstract
Accurate chromosome segregation in mitosis is crucial to maintain a diploid chromosome number. A majority of cancer cells are aneuploid and chromosomally unstable, i.e. they tend to gain and lose chromosomes at each mitotic division. Chromosome mis-segregation can arise when cells progress through mitosis with mis-attached kinetochores. Merotelic kinetochore orientation, a type of mis-attachment in which a single kinetochore binds microtubules from two spindle poles rather than just one, can represent a particular threat for dividing cells, as: (i) it occurs frequently in early mitosis; (ii) it is not detected by the spindle assembly checkpoint (unlike other types of mis-attachments); (iii) it can lead to chromosome mis-segregation, and, hence, aneuploidy. A number of studies have recently started to unveil the cellular and molecular mechanisms involved in merotelic kinetochore formation and correction. Here, I review these studies and discuss the relevance of merotelic kinetochore orientation in cancer cell biology.
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Affiliation(s)
- Daniela Cimini
- Virginia Tech, Department of Biological Sciences, 5036 Derring Hall, Blacksburg, VA 24061, USA.
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40
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Stanvitch G, Moore LL. cin-4, a gene with homology to topoisomerase II, is required for centromere resolution by cohesin removal from sister kinetochores during mitosis. Genetics 2008; 178:83-97. [PMID: 18202360 PMCID: PMC2206113 DOI: 10.1534/genetics.107.075275] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2007] [Accepted: 11/09/2007] [Indexed: 01/11/2023] Open
Abstract
The back-to-back geometry of sister kinetochores is essential in preventing loss or damage of chromosomes during mitosis. Kinetochore orientation is generated in part by a process of resolving kinetochores at the centromere (centromere resolution) prior to spindle interactions. Because few of the genes required for centromere resolution are known, we used Caenorhabditis elegans to screen for conditional mutants defective in orienting sister kinetochores during mitosis. C. elegans is ideal for such screens because its chromosomes are holocentric. Here we identified an essential gene, cin-4, required for centromere resolution and for removal of cohesin from sites near sister kinetochores during mitosis. Given that compromised cohesin function restores centromere resolution in the absence of cin-4, CIN-4 likely acts to remove cohesin from the CENP-A chromatin enabling centromere resolution. CIN-4 has a high amino acid identity to the catalytic domain of topoisomerase II, suggesting a partial gene duplication of the C. elegans topoisomerase II gene, top-2. Similar to CIN-4, TOP-2 is also required for centromere resolution; however, the loss of TOP-2 is phenotypically distinct from the loss of CIN-4, suggesting that CIN-4 and TOP-2 are topoisomerase II isoforms that perform separate essential functions in centromere structure and function.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Caenorhabditis elegans/cytology
- Caenorhabditis elegans/enzymology
- Caenorhabditis elegans/genetics
- Caenorhabditis elegans Proteins/chemistry
- Caenorhabditis elegans Proteins/genetics
- Caenorhabditis elegans Proteins/metabolism
- Catalytic Domain
- Cell Cycle Proteins/metabolism
- Chromosomal Instability
- Chromosomal Proteins, Non-Histone/metabolism
- Chromosomes/metabolism
- DNA Topoisomerases, Type II/chemistry
- DNA Topoisomerases, Type II/genetics
- DNA Topoisomerases, Type II/metabolism
- Embryo, Nonmammalian/cytology
- Embryo, Nonmammalian/metabolism
- Gene Duplication
- Genes, Helminth
- Kinetochores/metabolism
- Mitosis
- Models, Genetic
- Molecular Sequence Data
- Mutation/genetics
- Nuclear Proteins/metabolism
- Open Reading Frames/genetics
- Protein Transport
- RNA Interference
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Cohesins
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Affiliation(s)
- Gerald Stanvitch
- Department of Genetics and Genomics, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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41
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Oishi K, Okano H, Sawa H. RMD-1, a novel microtubule-associated protein, functions in chromosome segregation in Caenorhabditis elegans. ACTA ACUST UNITED AC 2007; 179:1149-62. [PMID: 18070910 PMCID: PMC2140014 DOI: 10.1083/jcb.200705108] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For proper chromosome segregation, the sister kinetochores must attach to microtubules extending from the opposite spindle poles. Any errors in microtubule attachment can induce aneuploidy. In this study, we identify a novel conserved Caenorhabditis elegans microtubule-associated protein, regulator of microtubule dynamics 1 (RMD-1), that localizes to spindle microtubules and spindle poles. Depletion of RMD-1 induces severe defects in chromosome segregation, probably through merotelic attachments between microtubules and chromosomes. Although rmd-1 embryos also have a mild defect in microtubule growth, we find that mutants of the microtubule growth regulator XMAP215/ZYG-9 show much weaker segregation defects. This suggests that the microtubule growth defect in rmd-1 embryos does not cause abnormal chromosome segregation. We also see that RMD-1 interacts with aurora B in vitro. Our results suggest that RMD-1 functions in chromosome segregation in C. elegans embryos, possibly through the aurora B–mediated pathway. Human homologues of RMD-1 could also bind microtubules, which would suggest a function for these proteins in chromosome segregation during mitosis in other organisms as well.
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Affiliation(s)
- Kumiko Oishi
- Laboratory for Cell Fate Decision, RIKEN Center for Developmental Biology, Chuo-ku, Kobe 650-0047, Japan
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Lam WW, Peterson EA, Yeung M, Lavoie BD. Condensin is required for chromosome arm cohesion during mitosis. Genes Dev 2006; 20:2973-84. [PMID: 17079686 PMCID: PMC1620018 DOI: 10.1101/gad.1468806] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Accepted: 08/31/2006] [Indexed: 11/24/2022]
Abstract
We describe a novel requirement for the condensin complex in sister chromatid cohesion in Saccharomyces cerevisiae. Strikingly, condensin-dependent cohesion can be distinguished from cohesin-based pairing by a number of criteria. First, condensin is required to maintain cohesion at several chromosomal arm sites but, in contrast to cohesin, is not required at either centromere or telomere-proximal loci. Second, condensin-dependent interlinks are established during mitosis independently of DNA replication and are reversible within a single cell cycle. Third, the loss of condensin-dependent linkages occurs without affecting cohesin levels at the separated URA3 locus. We propose that, during mitosis, robust sister chromatid cohesion along chromosome arms requires both condensinand cohesin-dependent mechanisms, which function independently of each other. We discuss the implications of our results for current models of sister chromatid cohesion.
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Affiliation(s)
- Wendy W Lam
- Department of Medical Genetics and Microbiology, University of Toronto, Toronto, Ontario, Canada
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Maddox PS, Portier N, Desai A, Oegema K. Molecular analysis of mitotic chromosome condensation using a quantitative time-resolved fluorescence microscopy assay. Proc Natl Acad Sci U S A 2006; 103:15097-102. [PMID: 17005720 PMCID: PMC1622782 DOI: 10.1073/pnas.0606993103] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Chromosomes condense during mitotic entry to facilitate their segregation. Condensation is typically assayed in fixed preparations, limiting analysis of contributing factors. Here, we describe a quantitative method to monitor condensation kinetics in living cells expressing GFP fused to a core histone. We demonstrate the utility of this method by using it to analyze the molecular requirements for the condensation of holocentric chromosomes during the first division of the Caenorhabditis elegans embryo. In control embryos, the fluorescence intensity distribution for nuclear GFP:histone changes during two distinct time intervals separated by a plateau phase. During the first interval, primary condensation converts diffuse chromatin into discrete linear chromosomes. After the plateau, secondary condensation compacts the curvilinear chromosomes to form shorter bar-shaped structures. We quantitatively compared the consequences on this characteristic profile of depleting the condensin complex, the mitosis-specific histone H3 kinase Aurora B, the centromeric histone CENP-A, and CENP-C, a conserved protein required for kinetochore assembly. Both condensin and CENP-A play critical but distinct roles in primary condensation. In contrast, depletion of CENP-C slows but does not prevent primary condensation. Finally, Aurora B inhibition has no effect on primary condensation, but slightly delays secondary condensation. These results provide insights into the process of condensation, help resolve apparent contradictions from prior studies, and indicate that CENP-A chromatin has an intrinsic role in the condensation of holocentric chromosomes that is independent of its requirement for kinetochore assembly.
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Affiliation(s)
- Paul S. Maddox
- *Ludwig Institute for Cancer Research
- Department of Cellular and Molecular Medicine, and
- To whom correspondence may be addressed. E-mail:
or
| | - Nathan Portier
- *Ludwig Institute for Cancer Research
- Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093
| | - Arshad Desai
- *Ludwig Institute for Cancer Research
- Department of Cellular and Molecular Medicine, and
- Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093
| | - Karen Oegema
- *Ludwig Institute for Cancer Research
- Department of Cellular and Molecular Medicine, and
- Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093
- To whom correspondence may be addressed. E-mail:
or
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Gerlich D, Hirota T, Koch B, Peters JM, Ellenberg J. Condensin I stabilizes chromosomes mechanically through a dynamic interaction in live cells. Curr Biol 2006; 16:333-44. [PMID: 16488867 DOI: 10.1016/j.cub.2005.12.040] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2005] [Revised: 12/07/2005] [Accepted: 12/20/2005] [Indexed: 11/23/2022]
Abstract
BACKGROUND Restructuring chromatin into morphologically distinct chromosomes is essential for cell division, but the molecular mechanisms underlying this process are poorly understood. Condensin complexes have been proposed as key factors, although controversial conclusions about their contribution to chromosome structure were reached by different experimental approaches in fixed cells or cell extracts. Their function under physiological conditions still needs to be defined. RESULTS Here, we investigated the specific functions of condensin I and II in live cells by fluorescence microscopy and RNAi depletion. Photobleaching and quantitative time-lapse imaging showed that GFP-tagged condensin II bound stably to chromosomes throughout mitosis. By contrast, the canonical condensin I interacted dynamically with chromatin after completion of prophase compaction, reaching steady-state levels on chromosomes before congression. In condensin I-depleted cells, compaction was normal, but chromosomes were mechanically labile and unable to withstand spindle forces during alignment. However, normal levels of condensin II were not required for chromosome stability. CONCLUSIONS We conclude that while condensin I seems dispensable for normal chromosome compaction, its dynamic binding after nuclear envelope breakdown locks already condensed chromatin in a rigid state required for mechanically stable spindle attachment.
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Affiliation(s)
- Daniel Gerlich
- Gene Expression and Cell Biology/Biophysics Programmes, EMBL, 69117 Heidelberg, Germany
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Carroll CW, Straight AF. Centromere formation: from epigenetics to self-assembly. Trends Cell Biol 2006; 16:70-8. [PMID: 16412639 DOI: 10.1016/j.tcb.2005.12.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Revised: 12/05/2005] [Accepted: 12/21/2005] [Indexed: 12/31/2022]
Abstract
This review is part of the Chromosome segregation and Aneuploidy series that focuses on the importance of chromosome segregation mechanisms in maintaining genome stability. Centromeres are specialized chromosomal domains that serve as the foundation for the mitotic kinetochore, the interaction site between the chromosome and the mitotic spindle. The chromatin of centromeres is distinguished from other chromosomal loci by the unique incorporation of the centromeric histone H3 variant, centromere protein A. Here, we review the genetic and epigenetic factors that control the formation and maintenance of centromeric chromatin and propose a chromatin self-assembly model for organizing the higher-order structure of the centromere.
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Affiliation(s)
- Christopher W Carroll
- Department of Biochemistry, Stanford University, Beckman Building, Rm. 409, 279 Campus Drive, Stanford, CA 94305-5307, USA
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Oliveira RA, Coelho PA, Sunkel CE. The condensin I subunit Barren/CAP-H is essential for the structural integrity of centromeric heterochromatin during mitosis. Mol Cell Biol 2005; 25:8971-84. [PMID: 16199875 PMCID: PMC1265781 DOI: 10.1128/mcb.25.20.8971-8984.2005] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During cell division, chromatin undergoes structural changes essential to ensure faithful segregation of the genome. Condensins, abundant components of mitotic chromosomes, are known to form two different complexes, condensins I and II. To further examine the role of condensin I in chromosome structure and in particular in centromere organization, we depleted from S2 cells the Drosophila CAP-H homologue Barren, a subunit exclusively associated with condensin I. In the absence of Barren/CAP-H the condensin core subunits DmSMC4/2 still associate with chromatin, while the other condensin I non-structural maintenance of chromosomes family proteins do not. Immunofluorescence and in vivo analysis of Barren/CAP-H-depleted cells showed that mitotic chromosomes are able to condense but fail to resolve sister chromatids. Additionally, Barren/CAP-H-depleted cells show chromosome congression defects that do not appear to be due to abnormal kinetochore-microtubule interaction. Instead, the centromeric and pericentromeric heterochromatin of Barren/CAP-H-depleted chromosomes shows structural problems. After bipolar attachment, the centromeric heterochromatin organized in the absence of Barren/CAP-H cannot withstand the forces exerted by the mitotic spindle and undergoes irreversible distortion. Taken together, our data suggest that the condensin I complex is required not only to promote sister chromatid resolution but also to maintain the structural integrity of centromeric heterochromatin during mitosis.
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Affiliation(s)
- Raquel A Oliveira
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Portugal
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47
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Abstract
The condensin complex has been implicated in the higher-order organization of mitotic chromosomes in a host of model eukaryotes from yeasts to flies and vertebrates. Although chromosomes paradoxically appear to condense in condensin mutants, chromatids are not properly resolved, resulting in chromosome segregation defects during anaphase. We have examined the role of different condensin complex components in interphase chromatin function by examining the effects of various condensin mutations on position-effect variegation in Drosophila melanogaster. Surprisingly, most mutations affecting condensin proteins were often found to result in strong enhancement of variegation in contrast to what might be expected for proteins believed to compact the genome. This suggests either that the role of condensin proteins in interphase differs from their expected role in mitosis or that the way we envision condensin's activity needs to be modified to accommodate alternative possibilities.
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Affiliation(s)
- Neville Cobbe
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
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48
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Abstract
Structural maintenance of chromosomes (SMC) proteins are chromosomal ATPases, highly conserved from bacteria to humans, that play fundamental roles in many aspects of higher-order chromosome organization and dynamics. In eukaryotes, SMC1 and SMC3 act as the core of the cohesin complexes that mediate sister chromatid cohesion, whereas SMC2 and SMC4 function as the core of the condensin complexes that are essential for chromosome assembly and segregation. Another complex containing SMC5 and SMC6 is implicated in DNA repair and checkpoint responses. The SMC complexes form unique ring- or V-shaped structures with long coiled-coil arms, and function as ATP-modulated, dynamic molecular linkers of the genome. Recent studies shed new light on the mechanistic action of these SMC machines and also expanded the repertoire of their diverse cellular functions. Dissecting this class of chromosomal ATPases is likely to be central to our understanding of the structural basis of genome organization, stability, and evolution.
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Affiliation(s)
- Ana Losada
- Spanish National Cancer Center (CNIO), Madrid
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Abstract
Condensins are multi-subunit protein complexes that play a central role in mitotic chromosome assembly and segregation. The complexes contain 'structural maintenance of chromosomes' (SMC) ATPase subunits, and induce DNA supercoiling and looping in an ATP-hydrolysis-dependent manner in vitro. Vertebrate cells have two different condensin complexes, condensins I and II, each containing a unique set of regulatory subunits. Condensin II participates in an early stage of chromosome condensation within the prophase nucleus. Condensin I gains access to chromosomes only after the nuclear envelope breaks down, and collaborates with condensin II to assemble metaphase chromosomes with fully resolved sister chromatids. The complexes also play critical roles in meiotic chromosome segregation and in interphase processes such as gene repression and checkpoint responses. In bacterial cells, ancestral forms of condensins control chromosome dynamics. Dissecting the diverse functions of condensins is likely to be central to our understanding of genome organization, stability and evolution.
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Affiliation(s)
- Tatsuya Hirano
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
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Moore LL, Stanvitch G, Roth MB, Rosen D. HCP-4/CENP-C promotes the prophase timing of centromere resolution by enabling the centromere association of HCP-6 in Caenorhabditis elegans. Mol Cell Biol 2005; 25:2583-92. [PMID: 15767665 PMCID: PMC1061647 DOI: 10.1128/mcb.25.7.2583-2592.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prior to microtubule capture, sister centromeres resolve from one another, coming to rest on opposite surfaces of the condensing chromosome. Subsequent assembly of sister kinetochores at each sister centromere generates a geometry favorable for equal levels of segregation of chromatids. The holocentric chromosomes of Caenorhabditis elegans are uniquely suited for the study of centromere resolution and subsequent kinetochore assembly. In C. elegans, only two proteins have been identified as being necessary for centromere resolution, the kinase AIR-2 (prophase only) and the centromere protein HCP-4/CENP-C. Here we found that the loss of proteins involved in chromosome cohesion bypassed the requirement for HCP-4/CENP-C but not for AIR-2. Interestingly, the loss of cohesin proteins also restored the localization of HCP-6 to the kinetochore. The loss of the condensin II protein HCP-6 or MIX-1/SMC2 impaired centromere resolution. Furthermore, the loss of HCP-6 or MIX-1/SMC2 resulted in no centromere resolution when either nocodazole or RNA interference (RNAi) of the kinetochore protein KNL-1 perturbed spindle-kinetochore interactions. This result suggests that normal prophase centromere resolution is mediated by condensin II proteins, which are actively recruited to sister centromeres to mediate the process of resolution.
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Affiliation(s)
- Landon L Moore
- Department of Genetics and Genomics, Boston University School of Medicine, 715 Albany St., E642, Boston, MA 02118, USA.
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