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Choppakatla P, Dekker B, Cutts EE, Vannini A, Dekker J, Funabiki H. Linker histone H1.8 inhibits chromatin binding of condensins and DNA topoisomerase II to tune chromosome length and individualization. eLife 2021; 10:e68918. [PMID: 34406118 PMCID: PMC8416026 DOI: 10.7554/elife.68918] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 08/13/2021] [Indexed: 12/14/2022] Open
Abstract
DNA loop extrusion by condensins and decatenation by DNA topoisomerase II (topo II) are thought to drive mitotic chromosome compaction and individualization. Here, we reveal that the linker histone H1.8 antagonizes condensins and topo II to shape mitotic chromosome organization. In vitro chromatin reconstitution experiments demonstrate that H1.8 inhibits binding of condensins and topo II to nucleosome arrays. Accordingly, H1.8 depletion in Xenopus egg extracts increased condensins and topo II levels on mitotic chromatin. Chromosome morphology and Hi-C analyses suggest that H1.8 depletion makes chromosomes thinner and longer through shortening the average loop size and reducing the DNA amount in each layer of mitotic loops. Furthermore, excess loading of condensins and topo II to chromosomes by H1.8 depletion causes hyper-chromosome individualization and dispersion. We propose that condensins and topo II are essential for chromosome individualization, but their functions are tuned by the linker histone to keep chromosomes together until anaphase.
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Affiliation(s)
- Pavan Choppakatla
- Laboratory of Chromosome and Cell Biology, The Rockefeller UniversityNew YorkUnited States
| | - Bastiaan Dekker
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical SchoolWorcesterUnited States
| | - Erin E Cutts
- Division of Structural Biology, The Institute of Cancer ResearchLondonUnited Kingdom
| | - Alessandro Vannini
- Division of Structural Biology, The Institute of Cancer ResearchLondonUnited Kingdom
- Fondazione Human Technopole, Structural Biology Research Centre, 20157MilanItaly
| | - Job Dekker
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical SchoolWorcesterUnited States
- Howard Hughes Medical InstituteChevy ChaseUnited States
| | - Hironori Funabiki
- Laboratory of Chromosome and Cell Biology, The Rockefeller UniversityNew YorkUnited States
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2
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Ha GS, Lee CM, Kim CW. Development of a Novel Nonradioisotopic Assay and Cdc25B Overexpression Cell Lines for Use in Screening for Cdc25B Inhibitors. Yonsei Med J 2018; 59:995-1003. [PMID: 30187708 PMCID: PMC6127434 DOI: 10.3349/ymj.2018.59.8.995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 08/03/2018] [Accepted: 08/09/2018] [Indexed: 12/30/2022] Open
Abstract
PURPOSE The cyclin-dependent kinase 1 (Cdk1) and cyclin B complex performs important roles in the transition from the G2 to M phase in the cell cycle through removal of inhibitory phosphates on Cdk1, and Cdc25B, which is a dual-specific phosphatase, mediates these dephosphorylation events. However, measuring Cdc25B activity by existing methods is hampered by inadequate nonspecific substrates and the need to use a radiolabeled isotope. The present study aimed to develop an improved method with which to properly measure Cdc25B activity using a novel nonradioisotopic assay and Cdc25B overexpression cell lines. MATERIALS AND METHODS A nonradioisotopic Cdk1 kinase assay, based on Western blotting for retinoblastoma protein and histone H1, was used to analyze Cdc25B activity. Also, stable Cdc25B2 and Cdc25B3 overexpression HeLa cell lines were constructed using the tetracycline-regulated expression system and were applied as a tool for screening for inhibitors of Cdc25B. RESULTS The present study developed and optimized a nonradioisotopic assay method to properly measure Cdc25B activity. Furthermore, we constructed stable Cdc25B2 and Cdc25B3 overexpression HeLa cell lines for the establishment of a strong assay system with which to evaluate the specificity of Cdc25B inhibitors under conditions similar to the intracellular environment. These methods were confirmed as useful tools for measuring Cdc25B activity. CONCLUSION The nonradioisotopic Cdk1 kinase assay and Cdc25B overexpression cell lines developed in this study can be conveniently used as tools for screening inhibitors of Cdc25B phosphatase as anticancer drugs.
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Affiliation(s)
- Gyong Sik Ha
- Biopharmaceutical Research Center, CJ Healthcare R&D Center, CJ HealthCare, Icheon, Korea
- Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Korea.
| | - Chung Min Lee
- Biopharmaceutical Research Center, CJ Healthcare R&D Center, CJ HealthCare, Icheon, Korea
- Graduate Program in Biomaterials Science and Engineering, College of Life Science and Biotechnology, Yonsei University, Seoul, Korea
- Vaccine Translational Research Center, Yonsei University, Seoul, Korea
| | - Chan Wha Kim
- Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Korea.
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3
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Liu C, Ma Y, Shang Y, Huo R, Li W. Post-translational regulation of the maternal-to-zygotic transition. Cell Mol Life Sci 2018; 75:1707-1722. [PMID: 29427077 PMCID: PMC11105290 DOI: 10.1007/s00018-018-2750-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 12/24/2017] [Accepted: 01/08/2018] [Indexed: 02/07/2023]
Abstract
The maternal-to-zygotic transition (MZT) is essential for the developmental control handed from maternal products to newly synthesized zygotic genome in the earliest stages of embryogenesis, including maternal component (mRNAs and proteins) degradation and zygotic genome activation (ZGA). Various protein post-translational modifications have been identified during the MZT, such as phosphorylation, methylation and ubiquitination. Precise post-translational regulation mechanisms are essential for the timely transition of early embryonic development. In this review, we summarize recent progress regarding the molecular mechanisms underlying post-translational regulation of maternal component degradation and ZGA during the MZT and discuss some important issues in the field.
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Affiliation(s)
- Chao Liu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, People's Republic of China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Yanjie Ma
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, People's Republic of China
- Department of Animal Science and Technology, Northeast Agricultural University, Haerbin, 150030, People's Republic of China
| | - Yongliang Shang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, People's Republic of China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Ran Huo
- State Key Laboratory of Reproductive Medicine, Department of Histology and Embryology, Nanjing Medical University, Nanjing, 210029, People's Republic of China.
- State Key Laboratory of Reproductive Medicine, Department of Histology and Embryology, Nanjing Medical University, Nanjing, 211166, People's Republic of China.
| | - Wei Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, People's Republic of China.
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
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4
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Jukam D, Shariati SAM, Skotheim JM. Zygotic Genome Activation in Vertebrates. Dev Cell 2017; 42:316-332. [PMID: 28829942 PMCID: PMC5714289 DOI: 10.1016/j.devcel.2017.07.026] [Citation(s) in RCA: 245] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/25/2017] [Accepted: 07/28/2017] [Indexed: 12/12/2022]
Abstract
The first major developmental transition in vertebrate embryos is the maternal-to-zygotic transition (MZT) when maternal mRNAs are degraded and zygotic transcription begins. During the MZT, the embryo takes charge of gene expression to control cell differentiation and further development. This spectacular organismal transition requires nuclear reprogramming and the initiation of RNAPII at thousands of promoters. Zygotic genome activation (ZGA) is mechanistically coordinated with other embryonic events, including changes in the cell cycle, chromatin state, and nuclear-to-cytoplasmic component ratios. Here, we review progress in understanding vertebrate ZGA dynamics in frogs, fish, mice, and humans to explore differences and emphasize common features.
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Affiliation(s)
- David Jukam
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - S Ali M Shariati
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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5
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Abstract
How eukaryotic genomes are packaged into compact cylindrical chromosomes in preparation for cell divisions has remained one of the major unsolved questions of cell biology. Novel approaches to study the topology of DNA helices inside the nuclei of intact cells, paired with computational modeling and precise biomechanical measurements of isolated chromosomes, have advanced our understanding of mitotic chromosome architecture. In this Review Essay, we discuss - in light of these recent insights - the role of chromatin architecture and the functions and possible mechanisms of SMC protein complexes and other molecular machines in the formation of mitotic chromosomes. Based on the information available, we propose a stepwise model of mitotic chromosome condensation that envisions the sequential generation of intra-chromosomal linkages by condensin complexes in the context of cohesin-mediated inter-chromosomal linkages, assisted by topoisomerase II. The described scenario results in rod-shaped metaphase chromosomes ready for their segregation to the cell poles.
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Affiliation(s)
- Marc Kschonsak
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
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6
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Miller KE, Heald R. Glutamylation of Nap1 modulates histone H1 dynamics and chromosome condensation in Xenopus. ACTA ACUST UNITED AC 2015; 209:211-20. [PMID: 25897082 PMCID: PMC4411273 DOI: 10.1083/jcb.201412097] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/25/2015] [Indexed: 01/05/2023]
Abstract
Nap1 is required for linker histone H1M-mediated mitotic chromosome condensation in Xenopus egg extracts, and glutamylation of Nap1 is required for proper deposition and turnover of H1M on chromatin during both interphase and mitosis. Linker histone H1 is required for mitotic chromosome architecture in Xenopus laevis egg extracts and, unlike core histones, exhibits rapid turnover on chromatin. Mechanisms regulating the recruitment, deposition, and dynamics of linker histones in mitosis are largely unknown. We found that the cytoplasmic histone chaperone nucleosome assembly protein 1 (Nap1) associates with the embryonic isoform of linker histone H1 (H1M) in egg extracts. Immunodepletion of Nap1 decreased H1M binding to mitotic chromosomes by nearly 50%, reduced H1M dynamics as measured by fluorescence recovery after photobleaching and caused chromosome decondensation similar to the effects of H1M depletion. Defects in H1M dynamics and chromosome condensation were rescued by adding back wild-type Nap1 but not a mutant lacking sites subject to posttranslational modification by glutamylation. Nap1 glutamylation increased the deposition of H1M on sperm nuclei and chromatin-coated beads, indicating that charge-shifting posttranslational modification of Nap1 contributes to H1M dynamics that are essential for higher order chromosome architecture.
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Affiliation(s)
- Kelly E Miller
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
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7
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Smits AH, Lindeboom RGH, Perino M, van Heeringen SJ, Veenstra GJC, Vermeulen M. Global absolute quantification reveals tight regulation of protein expression in single Xenopus eggs. Nucleic Acids Res 2014; 42:9880-91. [PMID: 25056316 PMCID: PMC4150773 DOI: 10.1093/nar/gku661] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
While recent developments in genomic sequencing technology have enabled comprehensive transcriptome analyses of single cells, single cell proteomics has thus far been restricted to targeted studies. Here, we perform global absolute protein quantification of fertilized Xenopus laevis eggs using mass spectrometry-based proteomics, quantifying over 5800 proteins in the largest single cell proteome characterized to date. Absolute protein amounts in single eggs are highly consistent, thus indicating a tight regulation of global protein abundance. Protein copy numbers in single eggs range from tens of thousands to ten trillion copies per cell. Comparison between the single-cell proteome and transcriptome reveal poor expression correlation. Finally, we identify 439 proteins that significantly change in abundance during early embryogenesis. Downregulated proteins include ribosomal proteins and upregulated proteins include basal transcription factors, among others. Many of these proteins do not show regulation at the transcript level. Altogether, our data reveal that the transcriptome is a poor indicator of the proteome and that protein levels are tightly controlled in X. laevis eggs.
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Affiliation(s)
- Arne H Smits
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands Cancer Genomics Netherlands, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Rik G H Lindeboom
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands Cancer Genomics Netherlands, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Matteo Perino
- Department of Developmental Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Simon J van Heeringen
- Department of Developmental Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Gert Jan C Veenstra
- Department of Developmental Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Michiel Vermeulen
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands Cancer Genomics Netherlands, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
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Hara Y, Iwabuchi M, Ohsumi K, Kimura A. Intranuclear DNA density affects chromosome condensation in metazoans. Mol Biol Cell 2013; 24:2442-53. [PMID: 23783035 PMCID: PMC3727936 DOI: 10.1091/mbc.e13-01-0043] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Quantification of mitotic chromosomes in Caenorhabditis elegans embryos and a Xenopus laevis egg extract system indicates that the chromosome amount per nuclear space, or “intranuclear DNA density,” regulates chromosome condensation. This suggests an adaptive mode of chromosome condensation regulation in metazoans. Chromosome condensation is critical for accurate inheritance of genetic information. The degree of condensation, which is reflected in the size of the condensed chromosomes during mitosis, is not constant. It is differentially regulated in embryonic and somatic cells. In addition to the developmentally programmed regulation of chromosome condensation, there may be adaptive regulation based on spatial parameters such as genomic length or cell size. We propose that chromosome condensation is affected by a spatial parameter called the chromosome amount per nuclear space, or “intranuclear DNA density.” Using Caenorhabditis elegans embryos, we show that condensed chromosome sizes vary during early embryogenesis. Of importance, changing DNA content to haploid or polyploid changes the condensed chromosome size, even at the same developmental stage. Condensed chromosome size correlates with interphase nuclear size. Finally, a reduction in nuclear size in a cell-free system from Xenopus laevis eggs resulted in reduced condensed chromosome sizes. These data support the hypothesis that intranuclear DNA density regulates chromosome condensation. This suggests an adaptive mode of chromosome condensation regulation in metazoans.
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Affiliation(s)
- Yuki Hara
- Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan
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9
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Abstract
PSCs (pluripotent stem cells) possess two key properties that have made them the focus of global research efforts in regenerative medicine: they have unlimited expansion potential under conditions which favour their preservation as PSCs and they have the ability to generate all somatic cell types upon differentiation (pluripotency). Conditions have been defined in vitro in which pluripotency is maintained, or else differentiation is favoured and is directed towards specific somatic cell types. However, an unanswered question is whether or not the core cell cycle machinery directly regulates the pluripotency and differentiation properties of PSCs. If so, then manipulation of the cell cycle may represent an additional tool by which in vitro maintenance or differentiation of PSCs may be controlled in regenerative medicine. The present review aims to summarize our current understanding of links between the core cell cycle machinery and the maintenance of pluripotency in ESCs (embryonic stem cells) and iPSCs (induced PSCs).
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10
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Xiao B, Freedman BS, Miller KE, Heald R, Marko JF. Histone H1 compacts DNA under force and during chromatin assembly. Mol Biol Cell 2012; 23:4864-71. [PMID: 23097493 PMCID: PMC3521692 DOI: 10.1091/mbc.e12-07-0518] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Histone H1 binds to linker DNA between nucleosomes, but the dynamics and biological ramifications of this interaction remain poorly understood. We performed single-molecule experiments using magnetic tweezers to determine the effects of H1 on naked DNA in buffer or during chromatin assembly in Xenopus egg extracts. In buffer, nanomolar concentrations of H1 induce bending and looping of naked DNA at stretching forces below 0.6 pN, effects that can be reversed with 2.7-pN force or in 200 mM monovalent salt concentrations. Consecutive tens-of-nanometer bending events suggest that H1 binds to naked DNA in buffer at high stoichiometries. In egg extracts, single DNA molecules assemble into nucleosomes and undergo rapid compaction. Histone H1 at endogenous physiological concentrations increases the DNA compaction rate during chromatin assembly under 2-pN force and decreases it during disassembly under 5-pN force. In egg cytoplasm, histone H1 protects sperm nuclei undergoing genome-wide decondensation and chromatin assembly from becoming abnormally stretched or fragmented due to astral microtubule pulling forces. These results reveal functional ramifications of H1 binding to DNA at the single-molecule level and suggest an important physiological role for H1 in compacting DNA under force and during chromatin assembly.
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Affiliation(s)
- Botao Xiao
- Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA.
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11
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Abstract
Cell size varies widely among different organisms as well as within the same organism in different tissue types and during development, which places variable metabolic and functional demands on organelles and internal structures. A fundamental question is how essential subcellular components scale to accommodate cell size differences. Nuclear transport has emerged as a conserved means of scaling nuclear size. A meiotic spindle scaling factor has been identified as the microtubule-severing protein katanin, which is differentially regulated by phosphorylation in two different-sized frog species. Anaphase mechanisms and levels of chromatin compaction both act to coordinate cell size with spindle and chromosome dimensions to ensure accurate genome distribution during cell division. Scaling relationships and mechanisms for many membrane-bound compartments remain largely unknown and are complicated by their heterogeneity and dynamic nature. This review summarizes cell and organelle size relationships and the experimental approaches that have elucidated mechanisms of intracellular scaling.
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Affiliation(s)
- Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071, USA.
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12
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Dikovskaya D, Khoudoli G, Newton IP, Chadha GS, Klotz D, Visvanathan A, Lamond A, Swedlow JR, Näthke IS. The adenomatous polyposis coli protein contributes to normal compaction of mitotic chromatin. PLoS One 2012; 7:e38102. [PMID: 22719865 PMCID: PMC3374815 DOI: 10.1371/journal.pone.0038102] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 05/03/2012] [Indexed: 11/23/2022] Open
Abstract
The tumour suppressor Adenomatous Polyposis Coli (APC) is required for proper mitosis; however, the exact role of APC in mitosis is not understood. Using demembranated sperm chromatin exposed to meiotic Xenopus egg extract and HeLa cells expressing fluorescently labelled histones, we established that APC contributes to chromatin compaction. Sperm chromatin in APC-depleted Xenopus egg extract frequently formed tight round or elongated structures. Such abnormally compacted chromatin predominantly formed spindles with low microtubule content. Furthermore, in mitotic HeLa cells expressing GFP- and mCherry-labelled H2B histones, depletion of APC caused a decrease in the donor fluorescence lifetime of neighbouring fluorophores, indicative of excessive chromatin compaction. Profiling the chromatin-associated proteome of sperm chromatin incubated with Xenopus egg extracts revealed temporal APC-dependent changes in the abundance of histones, closely mirrored by chromatin-associated Topoisomerase IIa, condensin I complex and Kif4. In the absence of APC these factors initially accumulated on chromatin, but then decreased faster than in controls. We also found and validated significant APC-dependent changes in chromatin modifiers Set-a and Rbbp7. Both were decreased on chromatin in APC-depleted extract; in addition, the kinetics of association of Set-a with chromatin was altered in the absence of APC.
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Affiliation(s)
- Dina Dikovskaya
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, United Kingdom
| | - Guennadi Khoudoli
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, Scotland, United Kingdom
| | - Ian P. Newton
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, United Kingdom
| | - Gaganmeet S. Chadha
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, Scotland, United Kingdom
| | - Daniel Klotz
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, United Kingdom
| | - Ashwat Visvanathan
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, Scotland, United Kingdom
| | - Angus Lamond
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, Scotland, United Kingdom
| | - Jason R. Swedlow
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, Scotland, United Kingdom
| | - Inke S. Näthke
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, United Kingdom
- * E-mail:
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13
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Abstract
As rapid divisions without growth generate progressively smaller cells within an embryo, mitotic chromosomes must also decrease in size to permit their proper segregation, but this scaling phenomenon is poorly understood. We demonstrated previously that nuclear and spindle size scale between egg extracts of the related frog species Xenopus tropicalis and Xenopus laevis, but show here that dimensions of isolated mitotic sperm chromosomes do not differ. This is consistent with the hypothesis that chromosome scaling does not occur in early embryonic development when cell and spindles sizes are large and anaphase B segregates chromosomes long distances. To recapitulate chromosome scaling during development, we combined nuclei isolated from different stage Xenopus laevis embryos with metaphase-arrested egg extracts. Mitotic chromosomes derived from nuclei of cleaving embryos through the blastula stage were similar in size to replicated sperm chromosomes, but decreased in area approximately 50% by the neurula stage, reproducing the trend in size changes observed in fixed embryos. Allowing G2 nuclei to swell in interphase prior to mitotic condensation did not increase mitotic chromosome size, but progression through a full cell cycle in egg extract did, suggesting that epigenetic mechanisms determining chromosome size can be altered during DNA replication. Comparison of different sized mitotic chromosomes assembled in vitro provides a tractable system to elucidate underlying molecular mechanisms.
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Affiliation(s)
- Esther K Kieserman
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
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14
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Chu CS, Hsu PH, Lo PW, Scheer E, Tora L, Tsai HJ, Tsai MD, Juan LJ. Protein kinase A-mediated serine 35 phosphorylation dissociates histone H1.4 from mitotic chromosome. J Biol Chem 2011; 286:35843-35851. [PMID: 21852232 PMCID: PMC3195632 DOI: 10.1074/jbc.m111.228064] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Global histone H1 phosphorylation correlates with cell cycle progression. However, the function of site-specific H1 variant phosphorylation remains unclear. Our mass spectrometry analysis revealed a novel N-terminal phosphorylation of the major H1 variant H1.4 at serine 35 (H1.4S35ph), which accumulates at mitosis immediately after H3 phosphorylation at serine 10. Protein kinase A (PKA) was found to be a kinase for H1.4S35. Importantly, Ser-35-phosphorylated H1.4 dissociates from mitotic chromatin. Moreover, H1.4S35A substitution mutant cannot efficiently rescue the mitotic defect following H1.4 depletion, and inhibition of PKA activity increases the mitotic chromatin compaction depending on H1.4. Our results not only indicate that PKA-mediated H1.4S35 phosphorylation dissociates H1.4 from mitotic chromatin but also suggest that this phosphorylation is necessary for specific mitotic functions.
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Affiliation(s)
- Chi-Shuen Chu
- Institute of Molecular Medicine, National Taiwan University, Taipei 100, Taiwan; Genomics Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Pang-Hung Hsu
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan; Department of Life Science, National Taiwan Ocean University, Keelung, Taiwan 20224; Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan 20224
| | - Pei-Wen Lo
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Elisabeth Scheer
- Program of Functional Genomics and Cancer, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR 7104, INSERM U964, Université de Strasbourg, BP 10142-67404 Illkirch Cedex, France
| | - Laszlo Tora
- Program of Functional Genomics and Cancer, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR 7104, INSERM U964, Université de Strasbourg, BP 10142-67404 Illkirch Cedex, France
| | - Hang-Jen Tsai
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Ming-Daw Tsai
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan; Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Li-Jung Juan
- Institute of Molecular Medicine, National Taiwan University, Taipei 100, Taiwan; Genomics Research Center, Academia Sinica, Taipei 115, Taiwan.
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15
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Freedman BS, Miller KE, Heald R. Xenopus egg extracts increase dynamics of histone H1 on sperm chromatin. PLoS One 2010; 5. [PMID: 20927327 PMCID: PMC2947519 DOI: 10.1371/journal.pone.0013111] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 09/03/2010] [Indexed: 01/03/2023] Open
Abstract
Background Linker histone H1 has been studied in vivo and using reconstituted chromatin, but there have been few systematic studies of the effects of the cellular environment on its function. Due to the presence of many other chromatin factors and specific chaperones such as RanBP7/importin beta that regulate histone H1, linker histones likely function differently in vivo than in purified systems. Methodology/Principal Findings We have directly compared H1 binding to sperm nuclei in buffer versus Xenopus egg extract cytoplasm, and monitored the effects of adding nuclear import chaperones. In buffer, RanBP7 decondenses sperm nuclei, while H1 binds tightly to the chromatin and rescues RanBP7-mediated decondensation. H1 binding is reduced in cytoplasm, and H1 exhibits rapid FRAP dynamics in cytoplasm but not in buffer. RanBP7 decreases H1 binding to chromatin in both buffer and extract but does not significantly affect H1 dynamics in either condition. Importin beta has a lesser effect than RanBP7 on sperm chromatin decondensation and H1 binding, while a combination of RanBP7/importin beta is no more effective than RanBP7 alone. In extracts supplemented with RanBP7, H1 localizes to chromosomal foci, which increase after DNA damage. Unlike somatic H1, the embryonic linker histone H1M binds equally well to chromatin in cytoplasm compared to buffer. Amino-globular and carboxyl terminal domains of H1M bind chromatin comparably to the full-length protein in buffer, but are inhibited ∼10-fold in cytoplasm. High levels of H1 or its truncations distort mitotic chromosomes and block their segregation during anaphase. Conclusion/Significance RanBP7 can decondense sperm nuclei and decrease H1 binding, but the rapid dynamics of H1 on chromatin depend on other cytoplasmic factors. Cytoplasm greatly impairs the activity of individual H1 domains, and only the full-length protein can condense chromatin properly. Our findings begin to bridge the gap between purified and in vivo chromatin systems.
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Affiliation(s)
- Benjamin S. Freedman
- Molecular and Cell Biology Department, University of California, Berkeley, California, United States of America
| | - Kelly E. Miller
- Molecular and Cell Biology Department, University of California, Berkeley, California, United States of America
| | - Rebecca Heald
- Molecular and Cell Biology Department, University of California, Berkeley, California, United States of America
- * E-mail:
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