1
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Kuzdere T, Flury V, Schalch T, Iesmantavicius V, Hess D, Bühler M. Differential phosphorylation of Clr4 SUV39H by Cdk1 accompanies a histone H3 methylation switch that is essential for gametogenesis. EMBO Rep 2022; 24:e55928. [PMID: 36408846 PMCID: PMC9827552 DOI: 10.15252/embr.202255928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/18/2022] [Accepted: 10/27/2022] [Indexed: 11/22/2022] Open
Abstract
Methylation of histone H3 at lysine 9 (H3K9) is a hallmark of heterochromatin that plays crucial roles in gene silencing, genome stability, and chromosome segregation. In Schizosaccharomyces pombe, Clr4 mediates both di- and tri-methylation of H3K9. Although H3K9 methylation has been intensely studied in mitotic cells, its role during sexual differentiation remains unclear. Here, we map H3K9 methylation genome-wide during meiosis and show that constitutive heterochromatin temporarily loses H3K9me2 and becomes H3K9me3 when cells commit to meiosis. Cells lacking the ability to tri-methylate H3K9 exhibit meiotic chromosome segregation defects. Finally, the H3K9 methylation switch is accompanied by differential phosphorylation of Clr4 by the cyclin-dependent kinase Cdk1. Our results suggest that a conserved master regulator of the cell cycle controls the specificity of an H3K9 methyltransferase to prevent ectopic H3K9 methylation and to ensure faithful gametogenesis.
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Affiliation(s)
- Tahsin Kuzdere
- Friedrich Miescher Institute for Biomedical ResearchBaselSwitzerland,University of BaselBaselSwitzerland
| | - Valentin Flury
- Friedrich Miescher Institute for Biomedical ResearchBaselSwitzerland,University of BaselBaselSwitzerland
| | - Thomas Schalch
- Department of Molecular and Cell Biology, Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLeicesterUK
| | | | - Daniel Hess
- Friedrich Miescher Institute for Biomedical ResearchBaselSwitzerland
| | - Marc Bühler
- Friedrich Miescher Institute for Biomedical ResearchBaselSwitzerland,University of BaselBaselSwitzerland
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2
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Velay F, Méteignier LV, Laloi C. You shall not pass! A Chromatin barrier story in plants. FRONTIERS IN PLANT SCIENCE 2022; 13:888102. [PMID: 36212303 PMCID: PMC9540200 DOI: 10.3389/fpls.2022.888102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 08/15/2022] [Indexed: 06/16/2023]
Abstract
As in other eukaryotes, the plant genome is functionally organized in two mutually exclusive chromatin fractions, a gene-rich and transcriptionally active euchromatin, and a gene-poor, repeat-rich, and transcriptionally silent heterochromatin. In Drosophila and humans, the molecular mechanisms by which euchromatin is preserved from heterochromatin spreading have been extensively studied, leading to the identification of insulator DNA elements and associated chromatin factors (insulator proteins), which form boundaries between chromatin domains with antagonistic features. In contrast, the identity of factors assuring such a barrier function remains largely elusive in plants. Nevertheless, several genomic elements and associated protein factors have recently been shown to regulate the spreading of chromatin marks across their natural boundaries in plants. In this minireview, we focus on recent findings that describe the spreading of chromatin and propose avenues to improve the understanding of how plant chromatin architecture and transitions between different chromatin domains are defined.
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Affiliation(s)
- Florent Velay
- Aix Marseille Université, CEA, CNRS, Biosciences and Biotechnologies Institute of Aix-Marseille (BIAM), Equipe de Luminy de Génétique et Biophysique des Plantes, Marseille, F-13009, France
| | - Louis-Valentin Méteignier
- Aix Marseille Université, CEA, CNRS, Biosciences and Biotechnologies Institute of Aix-Marseille (BIAM), Equipe de Luminy de Génétique et Biophysique des Plantes, Marseille, F-13009, France
- EA2106 Biomolécules et Biotechnologies Végétales, Université de Tours, Tours, France
| | - Christophe Laloi
- Aix Marseille Université, CEA, CNRS, Biosciences and Biotechnologies Institute of Aix-Marseille (BIAM), Equipe de Luminy de Génétique et Biophysique des Plantes, Marseille, F-13009, France
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3
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Biswas S, Chen Z, Karslake JD, Farhat A, Ames A, Raiymbek G, Freddolino PL, Biteen JS, Ragunathan K. HP1 oligomerization compensates for low-affinity H3K9me recognition and provides a tunable mechanism for heterochromatin-specific localization. SCIENCE ADVANCES 2022; 8:eabk0793. [PMID: 35857444 PMCID: PMC9269880 DOI: 10.1126/sciadv.abk0793] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 05/24/2022] [Indexed: 05/31/2023]
Abstract
HP1 proteins traverse a complex and crowded chromatin landscape to bind with low affinity but high specificity to histone H3K9 methylation (H3K9me) and form transcriptionally inactive genomic compartments called heterochromatin. Here, we visualize single-molecule dynamics of an HP1 homolog, the fission yeast Swi6, in its native chromatin environment. By tracking single Swi6 molecules, we identify mobility states that map to discrete biochemical intermediates. Using Swi6 mutants that perturb H3K9me recognition, oligomerization, or nucleic acid binding, we determine how each biochemical property affects protein dynamics. We estimate that Swi6 recognizes H3K9me3 with ~94-fold specificity relative to unmodified nucleosomes in living cells. While nucleic acid binding competes with Swi6 oligomerization, as few as four tandem chromodomains can overcome these inhibitory effects to facilitate Swi6 localization at heterochromatin formation sites. Our studies indicate that HP1 oligomerization is essential to form dynamic, higher-order complexes that outcompete nucleic acid binding to enable specific H3K9me recognition.
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Affiliation(s)
- Saikat Biswas
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ziyuan Chen
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104, USA
| | - Joshua D. Karslake
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104, USA
| | - Ali Farhat
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Amanda Ames
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Gulzhan Raiymbek
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Peter L. Freddolino
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Julie S. Biteen
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104, USA
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48104, USA
| | - Kaushik Ragunathan
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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4
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Topoisomerase VI participates in an insulator-like function that prevents H3K9me2 spreading. Proc Natl Acad Sci U S A 2022; 119:e2001290119. [PMID: 35759655 PMCID: PMC9271158 DOI: 10.1073/pnas.2001290119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The organization of the genome into transcriptionally active and inactive chromatin domains requires well-delineated chromatin boundaries and insulator functions in order to maintain the identity of adjacent genomic loci with antagonistic chromatin marks and functionality. In plants that lack known chromatin insulators, the mechanisms that prevent heterochromatin spreading into euchromatin remain to be identified. Here, we show that DNA Topoisomerase VI participates in a chromatin boundary function that safeguards the expression of genes in euchromatin islands within silenced heterochromatin regions. While some transposable elements are reactivated in mutants of the Topoisomerase VI complex, genes insulated in euchromatin islands within heterochromatic regions of the Arabidopsis thaliana genome are specifically down-regulated. H3K9me2 levels consistently increase at euchromatin island loci and decrease at some transposable element loci. We further show that Topoisomerase VI physically interacts with S-adenosylmethionine synthase methionine adenosyl transferase 3 (MAT3), which is required for H3K9me2. A Topoisomerase VI defect affects MAT3 occupancy on heterochromatic elements and its exclusion from euchromatic islands, thereby providing a possible mechanistic explanation to the essential role of Topoisomerase VI in the delimitation of chromatin domains.
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5
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Lu JY, Chang L, Li T, Wang T, Yin Y, Zhan G, Han X, Zhang K, Tao Y, Percharde M, Wang L, Peng Q, Yan P, Zhang H, Bi X, Shao W, Hong Y, Wu Z, Ma R, Wang P, Li W, Zhang J, Chang Z, Hou Y, Zhu B, Ramalho-Santos M, Li P, Xie W, Na J, Sun Y, Shen X. Homotypic clustering of L1 and B1/Alu repeats compartmentalizes the 3D genome. Cell Res 2021; 31:613-630. [PMID: 33514913 PMCID: PMC8169921 DOI: 10.1038/s41422-020-00466-6] [Citation(s) in RCA: 85] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 12/17/2020] [Indexed: 01/30/2023] Open
Abstract
Organization of the genome into euchromatin and heterochromatin appears to be evolutionarily conserved and relatively stable during lineage differentiation. In an effort to unravel the basic principle underlying genome folding, here we focus on the genome itself and report a fundamental role for L1 (LINE1 or LINE-1) and B1/Alu retrotransposons, the most abundant subclasses of repetitive sequences, in chromatin compartmentalization. We find that homotypic clustering of L1 and B1/Alu demarcates the genome into grossly exclusive domains, and characterizes and predicts Hi-C compartments. Spatial segregation of L1-rich sequences in the nuclear and nucleolar peripheries and B1/Alu-rich sequences in the nuclear interior is conserved in mouse and human cells and occurs dynamically during the cell cycle. In addition, de novo establishment of L1 and B1 nuclear segregation is coincident with the formation of higher-order chromatin structures during early embryogenesis and appears to be critically regulated by L1 and B1 transcripts. Importantly, depletion of L1 transcripts in embryonic stem cells drastically weakens homotypic repeat contacts and compartmental strength, and disrupts the nuclear segregation of L1- or B1-rich chromosomal sequences at genome-wide and individual sites. Mechanistically, nuclear co-localization and liquid droplet formation of L1 repeat DNA and RNA with heterochromatin protein HP1α suggest a phase-separation mechanism by which L1 promotes heterochromatin compartmentalization. Taken together, we propose a genetically encoded model in which L1 and B1/Alu repeats blueprint chromatin macrostructure. Our model explains the robustness of genome folding into a common conserved core, on which dynamic gene regulation is overlaid across cells.
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Affiliation(s)
- J. Yuyang Lu
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Lei Chang
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Biomedical Pioneering Innovation Center (BIOPIC), School of Life Sciences, and College of Future Technology, Peking University, Beijing, 100871 China ,grid.508040.9Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory), Guangzhou, Guangdong, 510005 China
| | - Tong Li
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Ting Wang
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Yafei Yin
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Ge Zhan
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Xue Han
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Ke Zhang
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Yibing Tao
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Michelle Percharde
- grid.14105.310000000122478951MRC London Institute of Medical Sciences (LMS), London, W120NN UK ,grid.7445.20000 0001 2113 8111Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, W120NN UK
| | - Liang Wang
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Qi Peng
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Pixi Yan
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Hui Zhang
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Xianju Bi
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Wen Shao
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Yantao Hong
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Zhongyang Wu
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Runze Ma
- grid.9227.e0000000119573309National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Peizhe Wang
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Wenzhi Li
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Jing Zhang
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Zai Chang
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Yingping Hou
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Biomedical Pioneering Innovation Center (BIOPIC), School of Life Sciences, and College of Future Technology, Peking University, Beijing, 100871 China
| | - Bing Zhu
- grid.9227.e0000000119573309National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Miguel Ramalho-Santos
- grid.17063.330000 0001 2157 2938Lunenfeld-Tanenbaum Research Institute, University of Toronto, Toronto, Ontario M5T 3H7 Canada
| | - Pilong Li
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Wei Xie
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Jie Na
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Yujie Sun
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Biomedical Pioneering Innovation Center (BIOPIC), School of Life Sciences, and College of Future Technology, Peking University, Beijing, 100871 China
| | - Xiaohua Shen
- grid.12527.330000 0001 0662 3178Tsinghua-Peking Joint Center for Life Sciences, School of Medicine and School of Life Sciences, Tsinghua University, Beijing, 100084 China
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6
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Zhang J, Yue W, Zhou Y, Liao M, Chen X, Hua J. Super enhancers-Functional cores under the 3D genome. Cell Prolif 2021; 54:e12970. [PMID: 33336467 PMCID: PMC7848964 DOI: 10.1111/cpr.12970] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 11/28/2020] [Accepted: 12/07/2020] [Indexed: 12/13/2022] Open
Abstract
Complex biochemical reactions take place in the nucleus all the time. Transcription machines must follow the rules. The chromatin state, especially the three-dimensional structure of the genome, plays an important role in gene regulation and expression. The super enhancers are important for defining cell identity in mammalian developmental processes and human diseases. It has been shown that the major components of transcriptional activation complexes are recruited by super enhancer to form phase-separated condensates. We summarize the current knowledge about super enhancer in the 3D genome. Furthermore, a new related transcriptional regulation model from super enhancer is outlined to explain its role in the mammalian cell progress.
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Affiliation(s)
- Juqing Zhang
- College of Veterinary MedicineShaanxi Centre of Stem Cells Engineering & TechnologyNorthwest A&F UniversityYanglingChina
| | - Wei Yue
- College of Veterinary MedicineShaanxi Centre of Stem Cells Engineering & TechnologyNorthwest A&F UniversityYanglingChina
| | - Yaqi Zhou
- College of Life ScienceNorthwest A&F UniversityYanglingChina
| | - Mingzhi Liao
- College of Life ScienceNorthwest A&F UniversityYanglingChina
| | - Xingqi Chen
- Department of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Jinlian Hua
- College of Veterinary MedicineShaanxi Centre of Stem Cells Engineering & TechnologyNorthwest A&F UniversityYanglingChina
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7
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The mouse HP1 proteins are essential for preventing liver tumorigenesis. Oncogene 2020; 39:2676-2691. [PMID: 32020053 DOI: 10.1038/s41388-020-1177-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 01/06/2020] [Accepted: 01/21/2020] [Indexed: 12/16/2022]
Abstract
Chromatin organization is essential for appropriate interpretation of the genetic information. Here, we demonstrated that the chromatin-associated proteins HP1 are dispensable for hepatocytes survival but are essential within hepatocytes to prevent liver tumor development in mice with HP1β being pivotal in these functions. Yet, we found that the loss of HP1 per se is not sufficient to induce cell transformation but renders cells more resistant to specific stress such as the expression of oncogenes and thus in fine, more prone to cell transformation. Molecular characterization of HP1-Triple KO premalignant livers and BMEL cells revealed that HP1 are essential for the maintenance of heterochromatin organization and for the regulation of specific genes with most of them having well characterized functions in liver functions and homeostasis. We further showed that some specific retrotransposons get reactivated upon loss of HP1, correlating with overexpression of genes in their neighborhood. Interestingly, we found that, although HP1-dependent genes are characterized by enrichment H3K9me3, this mark does not require HP1 for its maintenance and is not sufficient to maintain gene repression in absence of HP1. Finally, we demonstrated that the loss of TRIM28 association with HP1 recapitulated several phenotypes induced by the loss of HP1 including the reactivation of some retrotransposons and the increased incidence of liver cancer development. Altogether, our findings indicate that HP1 proteins act as guardians of liver homeostasis to prevent tumor development by modulating multiple chromatin-associated events within both the heterochromatic and euchromatic compartments, partly through regulation of the corepressor TRIM28 activity.
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8
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Rani R, Yaseen AM, Malwade A, Sevilimedu A. An RNA aptamer to HP1/Swi6 facilitates heterochromatin formation at an ectopic locus in S.pombe. RNA Biol 2019; 16:742-753. [PMID: 30794054 DOI: 10.1080/15476286.2019.1584026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
In the fission yeast Schizosaccharomyces pombe (S.pombe), heterochromatin domains are established and maintained by protein complexes that contain numerous RNA binding domains among their components. The fission yeast HP1 protein Swi6 is one such component and contains an unstructured RNA-binding hinge, which is important for the integrity and silencing of heterochromatin. In this study, we have used an RNA aptamer that likely binds to the Swi6 hinge with high affinity, as a tool to perturb the natural interactions mediated by this domain. When the hinge is blocked by the aptamer RNA, Swi6 appears to become less restricted to the pericentromeres and is enriched at specific euchromatic loci. This suggests a role for the Swi6 hinge, along with the chromoshadow domain (previously shown) in controlling the spread of heterochromatin in S.pombe. The study also highlights the potential of using a synthetic aptamer RNA as a tool to perturb nucleic acid - protein interaction in vivo with the objective of understanding the functional relevance of such an interaction.
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Affiliation(s)
- Rita Rani
- a Center for Innovation in Molecular and Pharmaceutical Sciences (CIMPS) , Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus , Telangana , India
| | - Abdul Mohd Yaseen
- a Center for Innovation in Molecular and Pharmaceutical Sciences (CIMPS) , Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus , Telangana , India
| | - Akshay Malwade
- a Center for Innovation in Molecular and Pharmaceutical Sciences (CIMPS) , Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus , Telangana , India
| | - Aarti Sevilimedu
- a Center for Innovation in Molecular and Pharmaceutical Sciences (CIMPS) , Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus , Telangana , India
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9
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Nambiar M, Smith GR. Pericentromere-Specific Cohesin Complex Prevents Meiotic Pericentric DNA Double-Strand Breaks and Lethal Crossovers. Mol Cell 2018; 71:540-553.e4. [PMID: 30078721 PMCID: PMC6097939 DOI: 10.1016/j.molcel.2018.06.035] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/13/2018] [Accepted: 06/22/2018] [Indexed: 11/17/2022]
Abstract
In most eukaryotes, meiotic crossovers are essential for error-free chromosome segregation but are specifically repressed near centromeres to prevent missegregation. Recognized for >85 years, the molecular mechanism of this repression has remained unknown. Meiotic chromosomes contain two distinct cohesin complexes: pericentric complex (for segregation) and chromosomal arm complex (for crossing over). We show that the pericentric-specific complex also actively represses pericentric meiotic double-strand break (DSB) formation and, consequently, crossovers. We uncover the mechanism by which fission yeast heterochromatin protein Swi6 (mammalian HP1-homolog) prevents recruitment of activators of meiotic DSB formation. Localizing missing activators to wild-type pericentromeres bypasses repression and generates abundant crossovers but reduces gamete viability. The molecular mechanism elucidated here likely extends to other species, including humans, where pericentric crossovers can result in disorders, such as Down syndrome. These mechanistic insights provide new clues to understand the roles played by multiple cohesin complexes, especially in human infertility and birth defects.
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Affiliation(s)
- Mridula Nambiar
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
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10
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Winick-Ng W, Rylett RJ. Into the Fourth Dimension: Dysregulation of Genome Architecture in Aging and Alzheimer's Disease. Front Mol Neurosci 2018. [PMID: 29541020 PMCID: PMC5835833 DOI: 10.3389/fnmol.2018.00060] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by synapse dysfunction and cognitive impairment. Understanding the development and progression of AD is challenging, as the disease is highly complex and multifactorial. Both environmental and genetic factors play a role in AD pathogenesis, highlighted by observations of complex DNA modifications at the single gene level, and by new evidence that also implicates changes in genome architecture in AD patients. The four-dimensional structure of chromatin in space and time is essential for context-dependent regulation of gene expression in post-mitotic neurons. Dysregulation of epigenetic processes have been observed in the aging brain and in patients with AD, though there is not yet agreement on the impact of these changes on transcription. New evidence shows that proteins involved in genome organization have altered expression and localization in the AD brain, suggesting that the genomic landscape may play a critical role in the development of AD. This review discusses the role of the chromatin organizers and epigenetic modifiers in post-mitotic cells, the aging brain, and in the development and progression of AD. How these new insights can be used to help determine disease risk and inform treatment strategies will also be discussed.
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Affiliation(s)
- Warren Winick-Ng
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada.,Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada
| | - R Jane Rylett
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada.,Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada
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11
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Berry S, Rosa S, Howard M, Bühler M, Dean C. Disruption of an RNA-binding hinge region abolishes LHP1-mediated epigenetic repression. Genes Dev 2017; 31:2115-2120. [PMID: 29212661 PMCID: PMC5749160 DOI: 10.1101/gad.305227.117] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 11/07/2017] [Indexed: 12/24/2022]
Abstract
In this study, Berry et al. investigated the functions of the different domains of LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) in Arabidopsis. They show that LHP1 binds RNA in vitro through the intrinsically disordered hinge region and show that both the hinge region and H3K27me3 recognition facilitate LHP1 localization and H3K27me3 maintenance. Epigenetic maintenance of gene repression is essential for development. Polycomb complexes are central to this memory, but many aspects of the underlying mechanism remain unclear. LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) binds Polycomb-deposited H3K27me3 and is required for repression of many Polycomb target genes in Arabidopsis. Here we show that LHP1 binds RNA in vitro through the intrinsically disordered hinge region. By independently perturbing the RNA-binding hinge region and H3K27me3 (trimethylation of histone H3 at Lys27) recognition, we found that both facilitate LHP1 localization and H3K27me3 maintenance. Disruption of the RNA-binding hinge region also prevented formation of subnuclear foci, structures potentially important for epigenetic repression.
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Affiliation(s)
- Scott Berry
- John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Stefanie Rosa
- Institute of Biochemistry and Biology, University of Potsdam, DE-14476 Potsdam-Golm, Germany
| | | | - Marc Bühler
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
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12
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Suhren JH, Noto T, Kataoka K, Gao S, Liu Y, Mochizuki K. Negative Regulators of an RNAi-Heterochromatin Positive Feedback Loop Safeguard Somatic Genome Integrity in Tetrahymena. Cell Rep 2017; 18:2494-2507. [PMID: 28273462 PMCID: PMC5357732 DOI: 10.1016/j.celrep.2017.02.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 12/22/2016] [Accepted: 02/06/2017] [Indexed: 11/05/2022] Open
Abstract
RNAi-mediated positive feedback loops are pivotal for the maintenance of heterochromatin, but how they are downregulated at heterochromatin-euchromatin borders is not well understood. In the ciliated protozoan Tetrahymena, heterochromatin is formed exclusively on the sequences that are removed from the somatic genome by programmed DNA elimination, and an RNAi-mediated feedback loop is important for assembling heterochromatin on the eliminated sequences. In this study, we show that the heterochromatin protein 1 (HP1)-like protein Coi6p, its interaction partners Coi7p and Lia5p, and the histone demethylase Jmj1p are crucial for confining the production of small RNAs and the formation of heterochromatin to the eliminated sequences. The loss of Coi6p, Coi7p, or Jmj1p causes ectopic DNA elimination. The results provide direct evidence for the existence of a dedicated mechanism that counteracts a positive feedback loop between RNAi and heterochromatin at heterochromatin-euchromatin borders to maintain the integrity of the somatic genome. The HP1-like protein Coi6p confines small RNA and heterochromatin formation Two Coi6p-binding proteins and the histone demethylase Jmj1p likely act with Coi6p Coi6p and Jmj1p are important for preventing ectopic DNA elimination Suppression of RNAi-heterochromatin feedback loop maintains somatic genome integrity
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Affiliation(s)
- Jan H Suhren
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, 1030 Vienna, Austria
| | - Tomoko Noto
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, 1030 Vienna, Austria; Institute of Human Genetics, CNRS-University of Montpellier UMR9002, 34396 Montpellier, France
| | - Kensuke Kataoka
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, 1030 Vienna, Austria
| | - Shan Gao
- Pathology Department, University of Michigan, Ann Arbor, MI 48109, USA
| | - Yifan Liu
- Pathology Department, University of Michigan, Ann Arbor, MI 48109, USA
| | - Kazufumi Mochizuki
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, 1030 Vienna, Austria; Institute of Human Genetics, CNRS-University of Montpellier UMR9002, 34396 Montpellier, France.
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13
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Acharya S, Hartmann M, Erhardt S. Chromatin-associated noncoding RNAs in development and inheritance. WILEY INTERDISCIPLINARY REVIEWS-RNA 2017; 8. [PMID: 28840663 DOI: 10.1002/wrna.1435] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/30/2017] [Accepted: 07/03/2017] [Indexed: 12/13/2022]
Abstract
Noncoding RNAs (ncRNAs) have emerged as crucial players in chromatin regulation. Their diversity allows them to partake in the regulation of numerous cellular processes across species. During development, long and short ncRNAs act in conjunction with each other where long ncRNAs (lncRNAs) are best understood in establishing appropriate gene expression patterns, while short ncRNAs (sRNAs) are known to establish constitutive heterochromatin and suppress mobile elements. Additionally, increasing evidence demonstrates roles of sRNAs in several typically lncRNA-mediated processes such as dosage compensation, indicating a complex regulatory network of noncoding RNAs. Together, various ncRNAs establish many mitotically heritable epigenetic marks during development. Additionally, they participate in mechanisms that regulate maintenance of these epigenetic marks during the lifespan of the organism. Interestingly, some epigenetic traits are transmitted to the next generation(s) via paramutations or transgenerational inheritance mediated by sRNAs. In this review, we give an overview of the various functions and regulations of ncRNAs and the mechanisms they employ in the establishment and maintenance of epigenetic marks and multi-generational transmission of epigenetic traits. WIREs RNA 2017, 8:e1435. doi: 10.1002/wrna.1435 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Sreemukta Acharya
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, and CellNetworks, Im Neuenheimer Feld 282, Heidelberg, Germany
| | - Mark Hartmann
- Regulation of Cellular Differentiation Group, Division of Epigenomics and Cancer Risk Factors, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Sylvia Erhardt
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, and CellNetworks, Im Neuenheimer Feld 282, Heidelberg, Germany
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14
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Vergara Z, Gutierrez C. Emerging roles of chromatin in the maintenance of genome organization and function in plants. Genome Biol 2017; 18:96. [PMID: 28535770 PMCID: PMC5440935 DOI: 10.1186/s13059-017-1236-9] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chromatin is not a uniform macromolecular entity; it contains different domains characterized by complex signatures of DNA and histone modifications. Such domains are organized both at a linear scale along the genome and spatially within the nucleus. We discuss recent discoveries regarding mechanisms that establish boundaries between chromatin states and nuclear territories. Chromatin organization is crucial for genome replication, transcriptional silencing, and DNA repair and recombination. The replication machinery is relevant for the maintenance of chromatin states, influencing DNA replication origin specification and accessibility. Current studies reinforce the idea of intimate crosstalk between chromatin features and processes involving DNA transactions.
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Affiliation(s)
- Zaida Vergara
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049, Madrid, Spain
| | - Crisanto Gutierrez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049, Madrid, Spain.
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15
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Phosphorylation of an HP1-like protein is a prerequisite for heterochromatin body formation in Tetrahymena DNA elimination. Proc Natl Acad Sci U S A 2016; 113:9027-32. [PMID: 27466409 DOI: 10.1073/pnas.1606012113] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multiple heterochromatic loci are often clustered into a higher order nuclear architecture called a heterochromatin body in diverse eukaryotes. Although phosphorylation of Heterochromatin Protein 1 (HP1) family proteins regulates heterochromatin dynamics, its role in heterochromatin bodies remains unknown. We previously reported that dephosphorylation of the HP1-like protein Pdd1p is required for the formation of heterochromatin bodies during the process of programmed DNA elimination in the ciliated protozoan Tetrahymena Here, we show that the heterochromatin body component Jub4p is required for Pdd1p phosphorylation, heterochromatin body formation, and DNA elimination. Moreover, our analyses of unphosphorylatable Pdd1p mutants demonstrate that Pdd1p phosphorylation is required for heterochromatin body formation and DNA elimination, whereas it is dispensable for local heterochromatin assembly. Therefore, both phosphorylation and the following dephosphorylation of Pdd1p are necessary to facilitate the formation of heterochromatin bodies. We suggest that Jub4p-mediated phosphorylation of Pdd1p creates a chromatin environment that is a prerequisite for subsequent heterochromatin body assembly and DNA elimination.
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16
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Gonzalez-Sandoval A, Gasser SM. Mechanism of chromatin segregation to the nuclear periphery in C. elegans embryos. WORM 2016; 5:e1190900. [PMID: 27695653 DOI: 10.1080/21624054.2016.1190900] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 05/06/2016] [Accepted: 05/13/2016] [Indexed: 10/21/2022]
Abstract
In eukaryotic organisms, gene regulation occurs in the context of chromatin. In the interphase nucleus, euchromatin and heterochromatin occupy distinct space during cell differentiation, with heterochromatin becoming enriched at the nuclear and nucleolar peripheries. This organization is thought to fine-tune gene expression. To elucidate the mechanisms that govern this level of genome organization, screens were carried out in C. elegans which monitored the loss of heterochromatin sequestration at the nuclear periphery. This led to the identification of a novel chromodomain protein, CEC-4 (Caenorhabditis elegans chromodomain protein 4) that mediates the anchoring of H3K9 methylation-bearing chromatin at the nuclear periphery in early to mid-stage embryos. Surprisingly, the loss of CEC-4 does not derepress genes found in heterochromatic domains, nor does it affect differentiation under standard laboratory conditions. On the other hand, CEC-4 contributes to the efficiency with which muscle differentiation is induced following ectopic expression of the master regulator, HLH-1. This is one of the first phenotypes specifically attributed to the ablation of heterochromatin anchoring.
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Affiliation(s)
- Adriana Gonzalez-Sandoval
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland; Faculty of Natural Sciences, University of Basel, Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland; Faculty of Natural Sciences, University of Basel, Basel, Switzerland
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17
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Wang J, Jia ST, Jia S. New Insights into the Regulation of Heterochromatin. Trends Genet 2016; 32:284-294. [PMID: 27005444 DOI: 10.1016/j.tig.2016.02.005] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 02/22/2016] [Accepted: 02/29/2016] [Indexed: 10/22/2022]
Abstract
All living organisms are constantly exposed to stresses from internal biological processes and surrounding environments, which induce many adaptive changes in cellular physiology and gene expression programs. Unexpectedly, constitutive heterochromatin, which is generally associated with the stable maintenance of gene silencing, is also dynamically regulated in response to stimuli. In this review we discuss the mechanism of constitutive heterochromatin assembly, its dynamic nature, and its responses to environmental changes.
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Affiliation(s)
- Jiyong Wang
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Sharon T Jia
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Songtao Jia
- Department of Biological Sciences, Columbia University, New York, NY, USA.
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18
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Harr JC, Gonzalez-Sandoval A, Gasser SM. Histones and histone modifications in perinuclear chromatin anchoring: from yeast to man. EMBO Rep 2016; 17:139-55. [PMID: 26792937 PMCID: PMC4783997 DOI: 10.15252/embr.201541809] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 12/21/2015] [Indexed: 01/01/2023] Open
Abstract
It is striking that within a eukaryotic nucleus, the genome can assume specific spatiotemporal distributions that correlate with the cell's functional states. Cell identity itself is determined by distinct sets of genes that are expressed at a given time. On the level of the individual gene, there is a strong correlation between transcriptional activity and associated histone modifications. Histone modifications act by influencing the recruitment of non-histone proteins and by determining the level of chromatin compaction, transcription factor binding, and transcription elongation. Accumulating evidence also shows that the subnuclear position of a gene or domain correlates with its expression status. Thus, the question arises whether this spatial organization results from or determines a gene's chromatin status. Although the association of a promoter with the inner nuclear membrane (INM) is neither necessary nor sufficient for repression, the perinuclear sequestration of heterochromatin is nonetheless conserved from yeast to man. How does subnuclear localization influence gene expression? Recent work argues that the common denominator between genome organization and gene expression is the modification of histones and in some cases of histone variants. This provides an important link between local chromatin structure and long-range genome organization in interphase cells. In this review, we will evaluate how histones contribute to the latter, and discuss how this might help to regulate genes crucial for cell differentiation.
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Affiliation(s)
- Jennifer C Harr
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Adriana Gonzalez-Sandoval
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland Faculty of Natural Sciences, University of Basel, Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland Faculty of Natural Sciences, University of Basel, Basel, Switzerland
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19
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Stunnenberg R, Kulasegaran-Shylini R, Keller C, Kirschmann MA, Gelman L, Bühler M. H3K9 methylation extends across natural boundaries of heterochromatin in the absence of an HP1 protein. EMBO J 2015; 34:2789-803. [PMID: 26438724 PMCID: PMC4682641 DOI: 10.15252/embj.201591320] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 09/03/2015] [Indexed: 12/13/2022] Open
Abstract
Proteins of the conserved HP1 family are elementary components of heterochromatin and are generally assumed to play a central role in the creation of a rigid, densely packed heterochromatic network that is inaccessible to the transcription machinery. Here, we demonstrate that the fission yeast HP1 protein Swi6 exists as a single highly dynamic population that rapidly exchanges in cis and in trans between different heterochromatic regions. Binding to methylated H3K9 or to heterochromatic RNA decelerates Swi6 mobility. We further show that Swi6 is largely dispensable to the maintenance of heterochromatin domains. In the absence of Swi6, H3K9 methylation levels are maintained by a mechanism that depends on polymeric self‐association properties of Tas3, a subunit of the RNA‐induced transcriptional silencing complex. Our results disclose a surprising role for Swi6 dimerization in demarcating constitutive heterochromatin from neighboring euchromatin. Thus, rather than promoting maintenance and spreading of heterochromatin, Swi6 appears to limit these processes and appropriately confine heterochromatin.
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Affiliation(s)
- Rieka Stunnenberg
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland University of Basel, Basel, Switzerland
| | | | - Claudia Keller
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland University of Basel, Basel, Switzerland
| | | | - Laurent Gelman
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Marc Bühler
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland University of Basel, Basel, Switzerland
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