1
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Sahu RK, Dhakshnamoorthy J, Jain S, Folco HD, Wheeler D, Grewal SIS. Nucleosome remodeler exclusion by histone deacetylation enforces heterochromatic silencing and epigenetic inheritance. Mol Cell 2024; 84:3175-3191.e8. [PMID: 39096900 DOI: 10.1016/j.molcel.2024.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2024] [Revised: 07/03/2024] [Accepted: 07/09/2024] [Indexed: 08/05/2024]
Abstract
Heterochromatin enforces transcriptional gene silencing and can be epigenetically inherited, but the underlying mechanisms remain unclear. Here, we show that histone deacetylation, a conserved feature of heterochromatin domains, blocks SWI/SNF subfamily remodelers involved in chromatin unraveling, thereby stabilizing modified nucleosomes that preserve gene silencing. Histone hyperacetylation, resulting from either the loss of histone deacetylase (HDAC) activity or the direct targeting of a histone acetyltransferase to heterochromatin, permits remodeler access, leading to silencing defects. The requirement for HDAC in heterochromatin silencing can be bypassed by impeding SWI/SNF activity. Highlighting the crucial role of remodelers, merely targeting SWI/SNF to heterochromatin, even in cells with functional HDAC, increases nucleosome turnover, causing defective gene silencing and compromised epigenetic inheritance. This study elucidates a fundamental mechanism whereby histone hypoacetylation, maintained by high HDAC levels in heterochromatic regions, ensures stable gene silencing and epigenetic inheritance, providing insights into genome regulatory mechanisms relevant to human diseases.
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Affiliation(s)
- Rakesh Kumar Sahu
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jothy Dhakshnamoorthy
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Shweta Jain
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Hernan Diego Folco
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - David Wheeler
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Shiv I S Grewal
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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2
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Sako K, Furukawa A, Nozawa RS, Kurita JI, Nishimura Y, Hirota T. Bipartite binding interface recruiting HP1 to chromosomal passenger complex at inner centromeres. J Cell Biol 2024; 223:e202312021. [PMID: 38781028 PMCID: PMC11116813 DOI: 10.1083/jcb.202312021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 04/05/2024] [Accepted: 05/09/2024] [Indexed: 05/25/2024] Open
Abstract
Maintenance of ploidy depends on the mitotic kinase Aurora B, the catalytic subunit of the chromosomal passenger complex (CPC) whose proficient activity is supported by HP1 enriched at inner centromeres. HP1 is known to associate with INCENP of the CPC in a manner that depends on the PVI motif conserved across HP1 interactors. Here, we found that the interaction of INCENP with HP1 requires not only the PVI motif but also its C-terminally juxtaposed domain. Remarkably, these domains conditionally fold the β-strand (PVI motif) and the α-helix from a disordered sequence upon HP1 binding and render INCENP with high affinity to HP1. This bipartite binding domain termed SSH domain (Structure composed of Strand and Helix) is necessary and sufficient to attain a predominant interaction of HP1 with INCENP. These results identify a unique HP1-binding module in INCENP that ensures enrichment of HP1 at inner centromeres, Aurora B activity, and thereby mitotic fidelity.
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Affiliation(s)
- Kosuke Sako
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Ayako Furukawa
- Graduate School of Medical Life Science, Yokohama City University, Yokohama, Japan
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Ryu-Suke Nozawa
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Jun-ichi Kurita
- Graduate School of Medical Life Science, Yokohama City University, Yokohama, Japan
| | - Yoshifumi Nishimura
- Graduate School of Medical Life Science, Yokohama City University, Yokohama, Japan
| | - Toru Hirota
- Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo, Japan
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3
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Chen Z, Seman M, Fyodorova Y, Farhat A, Ames A, Levashkevich A, Biswas S, Huang F, Freddolino L, Biteen JS, Ragunathan K. Tracking live-cell single-molecule dynamics enables measurements of heterochromatin-associated protein-protein interactions. Nucleic Acids Res 2024:gkae692. [PMID: 39142658 DOI: 10.1093/nar/gkae692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 07/17/2024] [Accepted: 08/01/2024] [Indexed: 08/16/2024] Open
Abstract
Visualizing and measuring molecular-scale interactions in living cells represents a major challenge, but recent advances in single-molecule super-resolution microscopy are bringing us closer to achieving this goal. Single-molecule super-resolution microscopy enables high-resolution and sensitive imaging of the positions and movement of molecules in living cells. HP1 proteins are important regulators of gene expression because they selectively bind and recognize H3K9 methylated (H3K9me) histones to form heterochromatin-associated protein complexes that silence gene expression, but several important mechanistic details of this process remain unexplored. Here, we extended live-cell single-molecule tracking studies in fission yeast to determine how HP1 proteins interact with their binding partners in the nucleus. We measured how genetic perturbations that affect H3K9me alter the diffusive properties of HP1 proteins and their binding partners, and we inferred their most likely interaction sites. Our results demonstrate that H3K9 methylation spatially restricts HP1 proteins and their interactors, thereby promoting ternary complex formation on chromatin while simultaneously suppressing off-chromatin binding. As opposed to being an inert platform to direct HP1 binding, our studies propose a novel function for H3K9me in promoting ternary complex formation by enhancing the specificity and stimulating the assembly of HP1-protein complexes in living cells.
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Affiliation(s)
- Ziyuan Chen
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Melissa Seman
- Department of Biology, Brandeis University, Waltham, MA 02451, USA
| | | | - Ali Farhat
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Amanda Ames
- Department of Biology, Brandeis University, Waltham, MA 02451, USA
| | | | - Saikat Biswas
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Fengting Huang
- Department of Biology, Brandeis University, Waltham, MA 02451, USA
| | - Lydia Freddolino
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Julie S Biteen
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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4
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Acs-Szabo L, Papp LA, Miklos I. Understanding the molecular mechanisms of human diseases: the benefits of fission yeasts. MICROBIAL CELL (GRAZ, AUSTRIA) 2024; 11:288-311. [PMID: 39104724 PMCID: PMC11299203 DOI: 10.15698/mic2024.08.833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 07/04/2024] [Accepted: 07/10/2024] [Indexed: 08/07/2024]
Abstract
The role of model organisms such as yeasts in life science research is crucial. Although the baker's yeast (Saccharomyces cerevisiae) is the most popular model among yeasts, the contribution of the fission yeasts (Schizosaccharomyces) to life science is also indisputable. Since both types of yeasts share several thousands of common orthologous genes with humans, they provide a simple research platform to investigate many fundamental molecular mechanisms and functions, thereby contributing to the understanding of the background of human diseases. In this review, we would like to highlight the many advantages of fission yeasts over budding yeasts. The usefulness of fission yeasts in virus research is shown as an example, presenting the most important research results related to the Human Immunodeficiency Virus Type 1 (HIV-1) Vpr protein. Besides, the potential role of fission yeasts in the study of prion biology is also discussed. Furthermore, we are keen to promote the uprising model yeast Schizosaccharomyces japonicus, which is a dimorphic species in the fission yeast genus. We propose the hyphal growth of S. japonicus as an unusual opportunity as a model to study the invadopodia of human cancer cells since the two seemingly different cell types can be compared along fundamental features. Here we also collect the latest laboratory protocols and bioinformatics tools for the fission yeasts to highlight the many possibilities available to the research community. In addition, we present several limiting factors that everyone should be aware of when working with yeast models.
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Affiliation(s)
- Lajos Acs-Szabo
- Department of Genetics and Applied Microbiology, Faculty of Science and Technology, University of DebrecenDebrecen, 4032Hungary
| | - Laszlo Attila Papp
- Department of Genetics and Applied Microbiology, Faculty of Science and Technology, University of DebrecenDebrecen, 4032Hungary
| | - Ida Miklos
- Department of Genetics and Applied Microbiology, Faculty of Science and Technology, University of DebrecenDebrecen, 4032Hungary
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5
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Ames A, Seman M, Larkin A, Raiymbek G, Chen Z, Levashkevich A, Kim B, Biteen JS, Ragunathan K. Epigenetic memory is governed by an effector recruitment specificity toggle in Heterochromatin Protein 1. Nat Commun 2024; 15:6276. [PMID: 39054315 PMCID: PMC11272775 DOI: 10.1038/s41467-024-50538-z] [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: 11/28/2023] [Accepted: 07/10/2024] [Indexed: 07/27/2024] Open
Abstract
HP1 proteins are essential for establishing and maintaining transcriptionally silent heterochromatin. They dimerize, forming a binding interface to recruit diverse chromatin-associated factors. Although HP1 proteins are known to rapidly evolve, the extent of variation required to achieve functional specialization is unknown. To investigate how changes in amino acid sequence impacts heterochromatin formation, we performed a targeted mutagenesis screen of the S. pombe HP1 homolog, Swi6. Substitutions within an auxiliary surface adjacent to the HP1 dimerization interface produce Swi6 variants with divergent maintenance properties. Remarkably, substitutions at a single amino acid position lead to the persistent gain or loss of epigenetic inheritance. These substitutions increase Swi6 chromatin occupancy in vivo and altered Swi6-protein interactions that reprogram H3K9me maintenance. We show how relatively minor changes in Swi6 amino acid composition in an auxiliary surface can lead to profound changes in epigenetic inheritance providing a redundant mechanism to evolve HP1-effector specificity.
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Affiliation(s)
- Amanda Ames
- Department of Biology, Brandeis University, Waltham, MA, 02453, USA
| | - Melissa Seman
- Department of Biology, Brandeis University, Waltham, MA, 02453, USA
| | - Ajay Larkin
- Department of Biology, Brandeis University, Waltham, MA, 02453, USA
| | - Gulzhan Raiymbek
- 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
| | | | - Bokyung Kim
- Department of Biochemistry, Brandeis University, Waltham, MA, 02453, USA
| | - Julie Suzanne Biteen
- Department of Biophysics, University of Michigan, Ann Arbor, MI, 48104, USA
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48104, USA
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6
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Ayhan DH, Abbondante S, Martínez-Soto D, Milo S, Rickelton K, Sohrab V, Kotera S, Arie T, Marshall ME, Rocha MC, Haridas S, Grigoriev IV, Shlezinger N, Pearlman E, Ma LJ. The differential virulence of Fusarium strains causing corneal infections and plant diseases is associated with accessory chromosome composition. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.23.595639. [PMID: 38826335 PMCID: PMC11142239 DOI: 10.1101/2024.05.23.595639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Fusarium oxysporum is a cross-kingdom pathogen. While some strains cause disseminated fusariosis and blinding corneal infections in humans, others are responsible for devastating vascular wilt diseases in plants. To better understand the distinct adaptations of F. oxysporum to animal or plant hosts, we conducted a comparative phenotypic and genetic analysis of two strains: MRL8996 (isolated from a keratitis patient) and Fol4287 (isolated from a wilted tomato [Solanum lycopersicum]). In vivo infection of mouse corneas and tomato plants revealed that, while both strains cause symptoms in both hosts, MRL8996 caused more severe corneal ulceration and perforation in mice, whereas Fol4287 induced more pronounced wilting symptoms in tomato. In vitro assays using abiotic stress treatments revealed that the human pathogen MRL8996 was better adapted to elevated temperatures, whereas the plant pathogen Fol4287 was more tolerant of osmotic and cell wall stresses. Both strains displayed broad resistance to antifungal treatment, with MRL8996 exhibiting the paradoxical effect of increased tolerance to higher concentrations of the antifungal caspofungin. We identified a set of accessory chromosomes (ACs) and protein-encoding genes with distinct transposon profiles and functions, respectively, between MRL8996 and Fol4287. Interestingly, ACs from both genomes also encode proteins with shared functions, such as chromatin remodeling and post-translational protein modifications. Our phenotypic assays and comparative genomics analyses lay the foundation for future studies correlating genotype with phenotype and for developing targeted antifungals for agricultural and clinical uses.
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Affiliation(s)
- Dilay Hazal Ayhan
- Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
- Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Serena Abbondante
- Physiology and Biophysics and Ophthalmology, University of California, Irvine, USA University of Massachusetts Amherst, Amherst, MA, USA
| | - Domingo Martínez-Soto
- Department of Microbiology, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico
| | - Shira Milo
- Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Katherine Rickelton
- Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
- Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Vista Sohrab
- Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Shunsuke Kotera
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Tokyo, Japan
| | - Tsutomu Arie
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Tokyo, Japan
| | - Michaela Ellen Marshall
- Physiology and Biophysics and Ophthalmology, University of California, Irvine, USA University of Massachusetts Amherst, Amherst, MA, USA
| | - Marina Campos Rocha
- The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Sajeet Haridas
- US Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Igor V. Grigoriev
- US Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Neta Shlezinger
- The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Eric Pearlman
- Physiology and Biophysics and Ophthalmology, University of California, Irvine, USA University of Massachusetts Amherst, Amherst, MA, USA
| | - Li-Jun Ma
- Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
- Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
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7
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Ames A, Seman M, Larkin A, Raiymbek G, Chen Z, Levashkevich A, Kim B, Biteen JS, Ragunathan K. Epigenetic memory is governed by an effector recruitment specificity toggle in Heterochromatin Protein 1. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.28.569027. [PMID: 38077059 PMCID: PMC10705379 DOI: 10.1101/2023.11.28.569027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
HP1 proteins are essential for establishing and maintaining transcriptionally silent heterochromatin. They dimerize, forming a binding interface to recruit diverse chromatin-associated factors. HP1 proteins are specialized and rapidly evolve, but the extent of variation required to achieve functional specialization is unknown. To investigate how changes in amino acid sequence impacts epigenetic inheritance, we performed a targeted mutagenesis screen of the S. pombe HP1 homolog, Swi6. Substitutions within an auxiliary surface adjacent to the HP1 dimerization interface produced Swi6 variants with divergent maintenance properties. Remarkably, substitutions at a single amino acid position led to the persistent gain or loss of epigenetic inheritance. These substitutions increased Swi6 chromatin occupancy in vivo and altered Swi6-protein interactions that reprogram H3K9me maintenance. We show that relatively minor changes in Swi6 amino acid composition can lead to profound changes in epigenetic inheritance which provides a redundant mechanism to evolve novel effector specificity. .
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8
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Yuan AH, Moazed D. Minimal requirements for the epigenetic inheritance of engineered silent chromatin domains. Proc Natl Acad Sci U S A 2024; 121:e2318455121. [PMID: 38198529 PMCID: PMC10801849 DOI: 10.1073/pnas.2318455121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Accepted: 12/06/2023] [Indexed: 01/12/2024] Open
Abstract
Mechanisms enabling genetically identical cells to differentially regulate gene expression are complex and central to organismal development and evolution. While gene silencing pathways involving DNA sequence-specific recruitment of histone-modifying enzymes are prevalent in nature, examples of sequence-independent heritable gene silencing are scarce. Studies of the fission yeast Schizosaccharomyces pombe indicate that sequence-independent propagation of heterochromatin can occur but requires numerous multisubunit protein complexes and their diverse activities. Such complexity has so far precluded a coherent articulation of the minimal requirements for heritable gene silencing by conventional in vitro reconstitution approaches. Here, we take an unconventional approach to defining these requirements by engineering sequence-independent silent chromatin inheritance in budding yeast Saccharomyces cerevisiae cells. The mechanism conferring memory upon these cells is remarkably simple and requires only two proteins, one that recognizes histone H3 lysine 9 methylation (H3K9me) and catalyzes the deacetylation of histone H4 lysine 16 (H4K16), and another that recognizes deacetylated H4K16 and catalyzes H3K9me. Together, these bilingual "read-write" proteins form an interdependent positive feedback loop that is sufficient for the transmission of DNA sequence-independent silent information over multiple generations.
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Affiliation(s)
- Andy H. Yuan
- HHMI, Harvard Medical School, Boston, MA02115
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA02115
| | - Danesh Moazed
- HHMI, Harvard Medical School, Boston, MA02115
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA02115
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9
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Jiang N, Li W, Jiang S, Xie M, Liu R. Acetylation in pathogenesis: Revealing emerging mechanisms and therapeutic prospects. Biomed Pharmacother 2023; 167:115519. [PMID: 37729729 DOI: 10.1016/j.biopha.2023.115519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 09/08/2023] [Accepted: 09/14/2023] [Indexed: 09/22/2023] Open
Abstract
Protein acetylation modifications play a central and pivotal role in a myriad of biological processes, spanning cellular metabolism, proliferation, differentiation, apoptosis, and beyond, by effectively reshaping protein structure and function. The metabolic state of cells is intricately connected to epigenetic modifications, which in turn influence chromatin status and gene expression patterns. Notably, pathological alterations in protein acetylation modifications are frequently observed in diseases such as metabolic syndrome, cardiovascular disorders, and cancer. Such abnormalities can result in altered protein properties and loss of function, which are closely associated with developing and progressing related diseases. In recent years, the advancement of precision medicine has highlighted the potential value of protein acetylation in disease diagnosis, treatment, and prevention. This review includes provocative and thought-provoking papers outlining recent breakthroughs in acetylation modifications as they relate to cardiovascular disease, mitochondrial metabolic regulation, liver health, neurological health, obesity, diabetes, and cancer. Additionally, it covers the molecular mechanisms and research challenges in understanding the role of acetylation in disease regulation. By summarizing novel targets and prognostic markers for the treatment of related diseases, we aim to contribute to the field. Furthermore, we discuss current hot topics in acetylation research related to health regulation, including N4-acetylcytidine and liquid-liquid phase separation. The primary objective of this review is to provide insights into the functional diversity and underlying mechanisms by which acetylation regulates proteins in disease contexts.
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Affiliation(s)
- Nan Jiang
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing 210009, China
| | - Wenyong Li
- School of Biology and Food Engineering, Fuyang Normal University, Fuyang, Anhui 236037, China
| | - Shuanglin Jiang
- School of Biology and Food Engineering, Fuyang Normal University, Fuyang, Anhui 236037, China
| | - Ming Xie
- North China Petroleum Bureau General Hospital, Renqiu 062550, China.
| | - Ran Liu
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing 210009, China.
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10
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Chen Z, Seman M, Farhat A, Fyodorova Y, Biswas S, Levashkevich A, Freddolino PL, Biteen JS, Ragunathan K. Tracking live-cell single-molecule dynamics enables measurements of heterochromatinassociated protein-protein interactions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.08.531771. [PMID: 36945633 PMCID: PMC10028927 DOI: 10.1101/2023.03.08.531771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Visualizing and measuring molecular-scale interactions in living cells represents a major challenge, but recent advances in microscopy are bringing us closer to achieving this goal. Single-molecule super-resolution microscopy enables high-resolution and sensitive imaging of the positions and movement of molecules in living cells. HP1 proteins are important regulators of gene expression because they selectively bind and recognize H3K9 methylated (H3K9me) histones to form heterochromatin-associated protein complexes that silence gene expression. Here, we extended live-cell single-molecule tracking studies in fission yeast to determine how HP1 proteins interact with their binding partners in the nucleus. We measured how genetic perturbations that affect H3K9me alter the diffusive properties of HP1 proteins and each of their binding partners based on which we inferred their most likely interaction sites. Our results indicate that H3K9me promotes specific complex formation between HP1 proteins and their interactors in a spatially restricted manner, while attenuating their ability to form off-chromatin complexes. As opposed to being an inert platform or scaffold to direct HP1 binding, our studies propose a novel function for H3K9me as an active participant in enhancing HP1-associated complex formation in living cells.
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Affiliation(s)
- Ziyuan Chen
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104 USA
| | - Melissa Seman
- Department of Biology, Brandeis University, Waltham, MA 02451 USA
| | - Ali Farhat
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109 USA
| | | | - Saikat Biswas
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48104 USA
- Current address: Pacific Biosciences, Menlo Park, CA 94025, USA
| | | | - P. Lydia Freddolino
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48104 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
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11
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Rahayu AF, Hayashi A, Yoshimura Y, Nakagawa R, Arita K, Nakayama JI. Cooperative DNA-binding activities of Chp2 are critical for its function in heterochromatin assembly. J Biochem 2023; 174:371-382. [PMID: 37400983 DOI: 10.1093/jb/mvad050] [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: 06/13/2023] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 07/05/2023] Open
Abstract
Heterochromatin protein 1 (HP1) is an evolutionarily conserved protein that plays a critical role in heterochromatin assembly. HP1 proteins share a basic structure consisting of an N-terminal chromodomain (CD) and a C-terminal chromoshadow domain (CSD) linked by a disordered hinge region. The CD recognizes histone H3 lysine 9 methylation, a hallmark of heterochromatin, while the CSD forms a dimer to recruit other chromosomal proteins. HP1 proteins have been shown to bind DNA or RNA primarily through the hinge region. However, how DNA or RNA binding contributes to their function remains elusive. Here, we focus on Chp2, one of the two HP1 proteins in fission yeast, and investigate how Chp2's DNA-binding ability contributes to its function. Similar to other HP1 proteins, the Chp2 hinge exhibits clear DNA-binding activity. Interestingly, the Chp2 CSD also shows robust DNA-binding activity. Mutational analysis revealed that basic residues in the Chp2 hinge and at the N-terminus of the CSD are essential for DNA binding, and the combined amino acid substitutions of these residues alter Chp2 stability, impair Chp2 heterochromatin localization and lead to a silencing defect. These results demonstrate that the cooperative DNA-binding activities of Chp2 play an important role in heterochromatin assembly in fission yeast.
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Affiliation(s)
- Anisa Fitri Rahayu
- Division of Chromatin Regulation, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
- Department of Basic Biology, School of Life Science, The Graduate University for Advanced Studies, SOKENDAI, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
| | - Aki Hayashi
- Division of Chromatin Regulation, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
| | - Yuriko Yoshimura
- Division of Chromatin Regulation, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
| | - Reiko Nakagawa
- Laboratory for Cell-Free Protein Synthesis, RIKEN Center for Biosystems Dynamics Research, 6-7-1 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
| | - Kyohei Arita
- Graduate School of Medical Life Science, Yokohama City University, 1-7-29, Suehiro-cho, Tsurumi-ku, Kanagawa 230-0045, Japan
| | - Jun-Ichi Nakayama
- Division of Chromatin Regulation, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
- Department of Basic Biology, School of Life Science, The Graduate University for Advanced Studies, SOKENDAI, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
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12
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Deacetylation induced nuclear condensation of HP1γ promotes multiple myeloma drug resistance. Nat Commun 2023; 14:1290. [PMID: 36894562 PMCID: PMC9998874 DOI: 10.1038/s41467-023-37013-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 02/24/2023] [Indexed: 03/11/2023] Open
Abstract
Acquired chemoresistance to proteasome inhibitors is a major obstacle in managing multiple myeloma but key regulators and underlying mechanisms still remain to be explored. We find that high level of HP1γ is associated with low acetylation modification in the bortezomib-resistant myeloma cells using SILAC-based acetyl-proteomics assay, and higher HP1γ level is positively correlated with poorer outcomes in the clinic. Mechanistically, elevated HDAC1 in the bortezomib-resistant myeloma cells deacetylates HP1γ at lysine 5 and consequently alleviates the ubiquitin-mediated protein degradation, as well as the aberrant DNA repair capacity. HP1γ interacts with the MDC1 to induce DNA repair, and simultaneously the deacetylation modification and the interaction with MDC1 enhance the nuclear condensation of HP1γ protein and the chromatin accessibility of its target genes governing sensitivity to proteasome inhibitors, such as CD40, FOS and JUN. Thus, targeting HP1γ stability by using HDAC1 inhibitor re-sensitizes bortezomib-resistant myeloma cells to proteasome inhibitors treatment in vitro and in vivo. Our findings elucidate a previously unrecognized role of HP1γ in inducing drug resistance to proteasome inhibitors of myeloma cells and suggest that targeting HP1γ may be efficacious for overcoming drug resistance in refractory or relapsed multiple myeloma patients.
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Opposing Roles of FACT for Euchromatin and Heterochromatin in Yeast. Biomolecules 2023; 13:biom13020377. [PMID: 36830746 PMCID: PMC9953268 DOI: 10.3390/biom13020377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/14/2023] [Accepted: 02/15/2023] [Indexed: 02/19/2023] Open
Abstract
DNA is stored in the nucleus of a cell in a folded state; however, only the necessary genetic information is extracted from the required group of genes. The key to extracting genetic information is chromatin ambivalence. Depending on the chromosomal region, chromatin is characterized into low-density "euchromatin" and high-density "heterochromatin", with various factors being involved in its regulation. Here, we focus on chromatin regulation and gene expression by the yeast FACT complex, which functions in both euchromatin and heterochromatin. FACT is known as a histone H2A/H2B chaperone and was initially reported as an elongation factor associated with RNA polymerase II. In budding yeast, FACT activates promoter chromatin by interacting with the transcriptional activators SBF/MBF via the regulation of G1/S cell cycle genes. In fission yeast, FACT plays an important role in the formation of higher-order chromatin structures and transcriptional repression by binding to Swi6, an HP1 family protein, at heterochromatin. This FACT property, which refers to the alternate chromatin-regulation depending on the binding partner, is an interesting phenomenon. Further analysis of nucleosome regulation within heterochromatin is expected in future studies.
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Zofall M, Sandhu R, Holla S, Wheeler D, Grewal SIS. Histone deacetylation primes self-propagation of heterochromatin domains to promote epigenetic inheritance. Nat Struct Mol Biol 2022; 29:898-909. [PMID: 36064597 DOI: 10.1038/s41594-022-00830-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 07/29/2022] [Indexed: 11/09/2022]
Abstract
Heterochromatin assembly, involving histone H3 lysine-9 methylation (H3K9me), is nucleated at specific genomic sites but can self-propagate across extended domains and, indeed, generations. Self-propagation requires Clr4/Suv39h methyltransferase recruitment by pre-existing H3K9 tri-methylation (H3K9me3) to perpetuate H3K9me deposition and is dramatically affected by chromatin context. However, the mechanism priming self-propagation of heterochromatin remains undefined. We show that robust chromatin association of fission yeast class II histone deacetylase Clr3 is necessary and sufficient to support heterochromatin propagation in different chromosomal contexts. Efficient targeting of Clr3, which suppresses histone turnover and maintains H3K9me3, enables self-propagation of an ectopic heterochromatin domain via the Clr4/Suv39h read-write mechanism requiring methylated histones. The deacetylase activity of Clr3 is necessary and, when inactivated, heterochromatin propagation can be recapitulated by removing two major histone acetyltransferases. Our results show that histone deacetylation, a conserved heterochromatin feature, preserves H3K9me3 that transmits epigenetic memory for stable propagation of silenced chromatin domains through multiple generations.
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Affiliation(s)
- Martin Zofall
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Rima Sandhu
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Sahana Holla
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - David Wheeler
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Shiv I S Grewal
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
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15
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Li Y, Song Z, Wang E, Dong L, Bai J, Wang D, Zhu J, Zhang C. Potential antifungal targets based on histones post-translational modifications against invasive aspergillosis. Front Microbiol 2022; 13:980615. [PMID: 36016791 PMCID: PMC9395700 DOI: 10.3389/fmicb.2022.980615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 07/27/2022] [Indexed: 11/17/2022] Open
Abstract
As a primary cause of death in patients with hematological malignancies and transplant recipients, invasive aspergillosis (IA) is a condition that warrants attention. IA infections have been increasing, which remains a significant cause of morbidity and mortality in immunocompromised patients. During the past decade, antifungal drug resistance has emerged, which is especially concerning for management given the limited options for treating azole-resistant infections and the possibility of failure of prophylaxis in those high-risk patients. Histone posttranslational modifications (HPTMs), mainly including acetylation, methylation, ubiquitination and phosphorylation, are crucial epigenetic mechanisms regulating various biological events, which could modify the conformation of histone and influence chromatin-associated nuclear processes to regulate development, cellular responsiveness, and biological phenotype without affecting the underlying genetic sequence. In recent years, fungi have become important model organisms for studying epigenetic regulation. HPTMs involves in growth and development, secondary metabolite biosynthesis and virulence in Aspergillus. This review mainly aims at summarizing the acetylation, deacetylation, methylation, demethylation, and sumoylation of histones in IA and connect this knowledge to possible HPTMs-based antifungal drugs. We hope this research could provide a reference for exploring new drug targets and developing low-toxic and high-efficiency antifungal strategies.
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Affiliation(s)
- Yiman Li
- Department of Pharmacy, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Zhihui Song
- Department of Pharmacy, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Ente Wang
- Department of Pharmacy, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Liming Dong
- Department of Pharmacy, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Jie Bai
- Department of Pharmacy, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Dong Wang
- Department of Pharmacy, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Jinyan Zhu
- Department of Hematology, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Chao Zhang
- Department of Pharmacy, Beijing Tongren Hospital, Capital Medical University, Beijing, China
- *Correspondence: Chao Zhang,
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16
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Stirpe A, Guidotti N, Northall SJ, Kilic S, Hainard A, Vadas O, Fierz B, Schalch T. SUV39 SET domains mediate crosstalk of heterochromatic histone marks. eLife 2021; 10:62682. [PMID: 34524082 PMCID: PMC8443253 DOI: 10.7554/elife.62682] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 08/31/2021] [Indexed: 12/21/2022] Open
Abstract
The SUV39 class of methyltransferase enzymes deposits histone H3 lysine 9 di- and trimethylation (H3K9me2/3), the hallmark of constitutive heterochromatin. How these enzymes are regulated to mark specific genomic regions as heterochromatic is poorly understood. Clr4 is the sole H3K9me2/3 methyltransferase in the fission yeast Schizosaccharomyces pombe, and recent evidence suggests that ubiquitination of lysine 14 on histone H3 (H3K14ub) plays a key role in H3K9 methylation. However, the molecular mechanism of this regulation and its role in heterochromatin formation remain to be determined. Our structure-function approach shows that the H3K14ub substrate binds specifically and tightly to the catalytic domain of Clr4, and thereby stimulates the enzyme by over 250-fold. Mutations that disrupt this mechanism lead to a loss of H3K9me2/3 and abolish heterochromatin silencing similar to clr4 deletion. Comparison with mammalian SET domain proteins suggests that the Clr4 SET domain harbors a conserved sensor for H3K14ub, which mediates licensing of heterochromatin formation.
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Affiliation(s)
- Alessandro Stirpe
- Department of Molecular Biology, Faculty of Science, University of Geneva, Geneva, Switzerland
| | - Nora Guidotti
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Sarah J Northall
- Leicester Institute for Structural and Chemical Biology, University of Leicester, Leicester, United Kingdom.,Department of Molecular and Cell Biology, University of Leicester, Leicester, United Kingdom
| | - Sinan Kilic
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Alexandre Hainard
- University Medical Center, University of Geneva, Geneva, Switzerland
| | - Oscar Vadas
- School of Pharmaceutical Sciences, Faculty of Science, University of Geneva, Geneva, Switzerland
| | - Beat Fierz
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Thomas Schalch
- Department of Molecular Biology, Faculty of Science, University of Geneva, Geneva, Switzerland.,Leicester Institute for Structural and Chemical Biology, University of Leicester, Leicester, United Kingdom.,Department of Molecular and Cell Biology, University of Leicester, Leicester, United Kingdom
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Breakers and amplifiers in chromatin circuitry: acetylation and ubiquitination control the heterochromatin machinery. Curr Opin Struct Biol 2021; 71:156-163. [PMID: 34303934 PMCID: PMC8667873 DOI: 10.1016/j.sbi.2021.06.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 06/06/2021] [Accepted: 06/13/2021] [Indexed: 11/30/2022]
Abstract
Eukaryotic genomes are segregated into active euchromatic and repressed heterochromatic compartments. Gene regulatory networks, chromosomal structures, and genome integrity rely on the timely and locus-specific establishment of active and silent states to protect the genome and provide the basis for cell division and specification of cellular identity. Here, we focus on the mechanisms and molecular machinery that establish heterochromatin in Schizosaccharomyces pombe and compare it with Saccharomyces cerevisiae and the mammalian polycomb system. We present recent structural and mechanistic evidence, which suggests that histone acetylation protects active transcription by disrupting the positive feedback loops used by the heterochromatin machinery and that H2A and H3 monoubiquitination actively drives heterochromatin, whereas H2B monoubiquitination mobilizes the defenses to quench heterochromatin. Heterochromatin-associated complexes are attracted and repelled by histone marks. Acetylation of specific lysine residues protects euchromatin from silencing. Methylation of histone H3 lysine 9 and 27 amplifies heterochromatin. Nucleosome ubiquitination licences and enforces feedback loops.
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18
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Abstract
Methylation of histone H3K9 is a hallmark of epigenetic silencing in eukaryotes. Nucleosome modifications often rely on positive feedback where enzymes are recruited by modified nucleosomes. A combination of local and global feedbacks has been proposed to account for some dynamic properties of heterochromatin, but the range at which the global feedbacks operate and the exact mode of heterochromatin propagation are not known. We investigated these questions in fission yeast. Guided by mathematical modeling, we incrementally increased the size of the mating-type region and profiled heterochromatin establishment over time. We observed exponential decays in the proportion of cells with active reporters, with rates that decreased with domain size. Establishment periods varied from a few generations in wild type to >200 generations in the longest region examined, and highly correlated silencing of two reporters located outside the nucleation center was observed. On a chromatin level, this indicates that individual regions are silenced in sudden bursts. Mathematical modeling accounts for these bursts if heterochromatic nucleosomes facilitate a deacetylation or methylation reaction at long range, in a distance-independent manner. A likely effector of three-dimensional interactions is the evolutionarily conserved Swi6HP1 H3K9me reader, indicating the bursting behavior might be a general mode of heterochromatin propagation.
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19
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Feng Y, Wang Y, Wang X, He X, Yang C, Naseri A, Pederson T, Zheng J, Zhang S, Xiao X, Xie W, Ma H. Simultaneous epigenetic perturbation and genome imaging reveal distinct roles of H3K9me3 in chromatin architecture and transcription. Genome Biol 2020; 21:296. [PMID: 33292531 PMCID: PMC7722448 DOI: 10.1186/s13059-020-02201-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 11/09/2020] [Indexed: 12/15/2022] Open
Abstract
INTRODUCTION Despite the long-observed correlation between H3K9me3, chromatin architecture, and transcriptional repression, how H3K9me3 regulates genome higher-order organization and transcriptional activity in living cells remains unclear. RESULT Here, we develop EpiGo (Epigenetic perturbation induced Genome organization)-KRAB to introduce H3K9me3 at hundreds of loci spanning megabases on human chromosome 19 and simultaneously track genome organization. EpiGo-KRAB is sufficient to induce genomic clustering and de novo heterochromatin-like domain formation, which requires SETDB1, a methyltransferase of H3K9me3. Unexpectedly, EpiGo-KRAB-induced heterochromatin-like domain does not result in widespread gene repression except a small set of genes with concurrent loss of H3K4me3 and H3K27ac. Ectopic H3K9me3 appears to spread in inactive regions but is largely restricted from transcriptional initiation sites in active regions. Finally, Hi-C analysis showed that EpiGo-KRAB reshapes existing compartments mainly at compartment boundaries. CONCLUSIONS These results reveal the role of H3K9me3 in genome organization could be partially separated from its function in gene repression.
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Affiliation(s)
- Ying Feng
- School of Biotechnology, East China University of Science and Technology, Shanghai, China; School of Life Science and Technology, ShanghaiTech University,, Shanghai, China
| | - Yao Wang
- Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Xiangnan Wang
- School of Life Science and Technology, ShanghaiTech University,, Beijing, China
| | - Xiaohui He
- School of Life Science and Technology, ShanghaiTech University,, Beijing, China
| | - Chen Yang
- School of Pharmacy, East China University of Science and Technology, Shanghai, China
| | - Ardalan Naseri
- Department of Computer Science, University of Central Florida, Orlando, FL, USA
| | - Thoru Pederson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jing Zheng
- School of Pharmacy, East China University of Science and Technology, Shanghai, China
| | - Shaojie Zhang
- Department of Computer Science, University of Central Florida, Orlando, FL, USA
| | - Xiao Xiao
- School of Biotechnology, East China University of Science and Technology,, Shanghai, China
| | - Wei Xie
- Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing, China.
- Tsinghua-Peking Center for Life Sciences, Beijing, China.
| | - Hanhui Ma
- School of Life Science and Technology, ShanghaiTech University,, Beijing, China.
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20
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Georgescu PR, Capella M, Fischer-Burkart S, Braun S. The euchromatic histone mark H3K36me3 preserves heterochromatin through sequestration of an acetyltransferase complex in fission yeast. MICROBIAL CELL 2020; 7:80-92. [PMID: 32161768 PMCID: PMC7052950 DOI: 10.15698/mic2020.03.711] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Maintaining the identity of chromatin states requires mechanisms that ensure their structural integrity through the concerted actions of histone modifiers, readers, and erasers. Histone H3K9me and H3K27me are hallmarks of repressed heterochromatin, whereas H3K4me and H3K36me are associated with actively transcribed euchromatin. Paradoxically, several studies have reported that loss of Set2, the methyltransferase responsible for H3K36me, causes de-repression of heterochromatin. Here we show that unconstrained activity of the acetyltransferase complex Mst2C, which antagonizes heterochromatin, is the main cause of the silencing defects observed in Set2-deficient cells. As previously shown, Mst2C is sequestered to actively transcribed chromatin via binding to H3K36me3 that is recognized by the PWWP domain protein Pdp3. We demonstrate that combining deletions of set2+ and pdp3+ results in an epistatic silencing phenotype. In contrast, deleting mst2+, or other members of Mst2C, fully restores silencing in Set2-deficient cells. Suppression of the silencing defect in set2Δ cells is specific for pericentromeres and subtelomeres, which are marked by H3K9me, but is not seen for loci that lack genuine heterochromatin. Mst2 is known to acetylate histone H3K14 redundantly with the HAT Gnc5. Further, it is involved in the acetylation of the non-histone substrate and E3 ubiquitin ligase Brl1, resulting in increased H2B-K119 ubiquitylation at euchromatin. However, we reveal that none of these mechanisms are responsible for the Set2-dependent silencing pathway, implying that Mst2 targets another, unknown substrate critical for heterochromatin silencing. Our findings demonstrate that maintenance of chromatin states requires spatial constraint of opposing chromatin activities.
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Affiliation(s)
- Paula R Georgescu
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
| | - Matías Capella
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
| | - Sabine Fischer-Burkart
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
| | - Sigurd Braun
- Department of Physiological Chemistry, BioMedical Center (BMC), Ludwig-Maximilians-Universität München, Martinsried, Germany
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