51
|
Llorens-Giralt P, Camilleri-Robles C, Corominas M, Climent-Cantó P. Chromatin Organization and Function in Drosophila. Cells 2021; 10:cells10092362. [PMID: 34572010 PMCID: PMC8465611 DOI: 10.3390/cells10092362] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/03/2021] [Accepted: 09/06/2021] [Indexed: 12/25/2022] Open
Abstract
Eukaryotic genomes are packaged into high-order chromatin structures organized in discrete territories inside the cell nucleus, which is surrounded by the nuclear envelope acting as a barrier. This chromatin organization is complex and dynamic and, thus, determining the spatial and temporal distribution and folding of chromosomes within the nucleus is critical for understanding the role of chromatin topology in genome function. Primarily focusing on the regulation of gene expression, we review here how the genome of Drosophila melanogaster is organized into the cell nucleus, from small scale histone–DNA interactions to chromosome and lamina interactions in the nuclear space.
Collapse
|
52
|
Tamburri S, Conway E, Pasini D. Polycomb-dependent histone H2A ubiquitination links developmental disorders with cancer. Trends Genet 2021; 38:333-352. [PMID: 34426021 DOI: 10.1016/j.tig.2021.07.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/21/2021] [Accepted: 07/26/2021] [Indexed: 12/18/2022]
Abstract
Cell identity is tightly controlled by specific transcriptional programs which require post-translational modifications of histones. These histone modifications allow the establishment and maintenance of active and repressed chromatin domains. Histone H2A lysine 119 ubiquitination (H2AK119ub1) has an essential role in building repressive chromatin domains during development. It is regulated by the counteracting activities of the Polycomb repressive complex 1 (PRC1) and the Polycomb repressive-deubiquitinase (PR-DUB) complexes, two multi-subunit ensembles that write and erase this modification, respectively. We have catalogued the recurrent genetic alterations in subunits of the PRC1 and PR-DUB complexes in both neurodevelopmental disorders and cancer. These genetic lesions are often shared across disorders, and we highlight common mechanisms of H2AK119ub1 dysregulation and how they affect development in multiple disease contexts.
Collapse
Affiliation(s)
- Simone Tamburri
- European Institute of Oncology (IEO), Istituto Di Ricovero e Cura a Carattere Scientifico (IRCCS), Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy; University of Milan, Department of Health Sciences, Via Antonio di Rudinì 8, 20142 Milan, Italy.
| | - Eric Conway
- European Institute of Oncology (IEO), Istituto Di Ricovero e Cura a Carattere Scientifico (IRCCS), Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Diego Pasini
- European Institute of Oncology (IEO), Istituto Di Ricovero e Cura a Carattere Scientifico (IRCCS), Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy; University of Milan, Department of Health Sciences, Via Antonio di Rudinì 8, 20142 Milan, Italy.
| |
Collapse
|
53
|
Lee JH, Wang R, Xiong F, Krakowiak J, Liao Z, Nguyen PT, Moroz-Omori EV, Shao J, Zhu X, Bolt MJ, Wu H, Singh PK, Bi M, Shi CJ, Jamal N, Li G, Mistry R, Jung SY, Tsai KL, Ferreon JC, Stossi F, Caflisch A, Liu Z, Mancini MA, Li W. Enhancer RNA m6A methylation facilitates transcriptional condensate formation and gene activation. Mol Cell 2021; 81:3368-3385.e9. [PMID: 34375583 PMCID: PMC8383322 DOI: 10.1016/j.molcel.2021.07.024] [Citation(s) in RCA: 137] [Impact Index Per Article: 45.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 06/10/2021] [Accepted: 07/20/2021] [Indexed: 01/22/2023]
Abstract
The mechanistic understanding of nascent RNAs in transcriptional control remains limited. Here, by a high sensitivity method methylation-inscribed nascent transcripts sequencing (MINT-seq), we characterized the landscapes of N6-methyladenosine (m6A) on nascent RNAs. We uncover heavy but selective m6A deposition on nascent RNAs produced by transcription regulatory elements, including promoter upstream antisense RNAs and enhancer RNAs (eRNAs), which positively correlates with their length, inclusion of m6A motif, and RNA abundances. m6A-eRNAs mark highly active enhancers, where they recruit nuclear m6A reader YTHDC1 to phase separate into liquid-like condensates, in a manner dependent on its C terminus intrinsically disordered region and arginine residues. The m6A-eRNA/YTHDC1 condensate co-mixes with and facilitates the formation of BRD4 coactivator condensate. Consequently, YTHDC1 depletion diminished BRD4 condensate and its recruitment to enhancers, resulting in inhibited enhancer and gene activation. We propose that chemical modifications of eRNAs together with reader proteins play broad roles in enhancer activation and gene transcriptional control.
Collapse
Affiliation(s)
- Joo-Hyung Lee
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Ruoyu Wang
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center and UTHealth, Houston, TX 77030, USA
| | - Feng Xiong
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Joanna Krakowiak
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Zian Liao
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center and UTHealth, Houston, TX 77030, USA
| | - Phuoc T Nguyen
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center and UTHealth, Houston, TX 77030, USA
| | - Elena V Moroz-Omori
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Jiaofang Shao
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Xiaoyu Zhu
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Michael J Bolt
- Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, TX 77030, USA; Gulf Coast Consortia Center for Advanced Microscopy and Image Informatics, Houston, TX 77030, USA
| | - Haoyi Wu
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center and UTHealth, Houston, TX 77030, USA
| | - Pankaj K Singh
- Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, TX 77030, USA; Gulf Coast Consortia Center for Advanced Microscopy and Image Informatics, Houston, TX 77030, USA
| | - Mingjun Bi
- Department of Molecular Medicine, Mays Cancer Center, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Caleb J Shi
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Naadir Jamal
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Guojie Li
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Ragini Mistry
- Gulf Coast Consortia Center for Advanced Microscopy and Image Informatics, Houston, TX 77030, USA; Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sung Yun Jung
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Kuang-Lei Tsai
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Josephine C Ferreon
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Fabio Stossi
- Gulf Coast Consortia Center for Advanced Microscopy and Image Informatics, Houston, TX 77030, USA; Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Amedeo Caflisch
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Zhijie Liu
- Department of Molecular Medicine, Mays Cancer Center, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Michael A Mancini
- Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, TX 77030, USA; Gulf Coast Consortia Center for Advanced Microscopy and Image Informatics, Houston, TX 77030, USA; Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA
| | - Wenbo Li
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center and UTHealth, Houston, TX 77030, USA.
| |
Collapse
|
54
|
Brown K, Andrianakos H, Ingersoll S, Ren X. Single-molecule imaging of epigenetic complexes in living cells: insights from studies on Polycomb group proteins. Nucleic Acids Res 2021; 49:6621-6637. [PMID: 34009336 PMCID: PMC8266577 DOI: 10.1093/nar/gkab304] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 04/09/2021] [Accepted: 04/13/2021] [Indexed: 12/30/2022] Open
Abstract
Chromatin-associated factors must locate, bind to, and assemble on specific chromatin regions to execute chromatin-templated functions. These dynamic processes are essential for understanding how chromatin achieves regulation, but direct quantification in living mammalian cells remains challenging. Over the last few years, live-cell single-molecule tracking (SMT) has emerged as a new way to observe trajectories of individual chromatin-associated factors in living mammalian cells, providing new perspectives on chromatin-templated activities. Here, we discuss the relative merits of live-cell SMT techniques currently in use. We provide new insights into how Polycomb group (PcG) proteins, master regulators of development and cell differentiation, decipher genetic and epigenetic information to achieve binding stability and highlight that Polycomb condensates facilitate target-search efficiency. We provide perspectives on liquid-liquid phase separation in organizing Polycomb targets. We suggest that epigenetic complexes integrate genetic and epigenetic information for target binding and localization and achieve target-search efficiency through nuclear organization.
Collapse
Affiliation(s)
- Kyle Brown
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | | | - Steven Ingersoll
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Xiaojun Ren
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| |
Collapse
|
55
|
Oss-Ronen L, Cohen I. Epigenetic regulation and signalling pathways in Merkel cell development. Exp Dermatol 2021; 30:1051-1064. [PMID: 34152646 DOI: 10.1111/exd.14415] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 06/15/2021] [Accepted: 06/17/2021] [Indexed: 12/20/2022]
Abstract
Merkel cells are specialized epithelial cells connected to afferent nerve endings responsible for light-touch sensations, formed at specific locations in touch-sensitive regions of the mammalian skin. Although Merkel cells are descendants of the epidermal lineage, little is known about the mechanisms responsible for the development of these unique mechanosensory cells. Recent studies have highlighted that the Polycomb group (PcG) of proteins play a significant role in spatiotemporal regulation of Merkel cell formation. In addition, several of the major signalling pathways involved in skin development have been shown to regulate Merkel cell development as well. Here, we summarize the current understandings of the role of developmental regulators in Merkel cell formation, including the interplay between the epigenetic machinery and key signalling pathways, and the lineage-specific transcription factors involved in the regulation of Merkel cell development.
Collapse
Affiliation(s)
- Liat Oss-Ronen
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Science, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Idan Cohen
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Science, Ben-Gurion University of the Negev, Beer Sheva, Israel
| |
Collapse
|
56
|
Xu J, Zhao X, Mao F, Basrur V, Ueberheide B, Chait BT, Allis CD, Taverna SD, Gao S, Wang W, Liu Y. A Polycomb repressive complex is required for RNAi-mediated heterochromatin formation and dynamic distribution of nuclear bodies. Nucleic Acids Res 2021; 49:5407-5425. [PMID: 33412588 PMCID: PMC8191774 DOI: 10.1093/nar/gkaa1262] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 12/02/2020] [Accepted: 01/04/2021] [Indexed: 01/17/2023] Open
Abstract
Polycomb group (PcG) proteins are widely utilized for transcriptional repression in eukaryotes. Here, we characterize, in the protist Tetrahymena thermophila, the EZL1 (E(z)-like 1) complex, with components conserved in metazoan Polycomb Repressive Complexes 1 and 2 (PRC1 and PRC2). The EZL1 complex is required for histone H3 K27 and K9 methylation, heterochromatin formation, transposable element control, and programmed genome rearrangement. The EZL1 complex interacts with EMA1, a helicase required for RNA interference (RNAi). This interaction is implicated in co-transcriptional recruitment of the EZL1 complex. Binding of H3K27 and H3K9 methylation by PDD1-another PcG protein interacting with the EZL1 complex-reinforces its chromatin association. The EZL1 complex is an integral part of Polycomb bodies, which exhibit dynamic distribution in Tetrahymena development: Their dispersion is driven by chromatin association, while their coalescence by PDD1, likely via phase separation. Our results provide a molecular mechanism connecting RNAi and Polycomb repression, which coordinately regulate nuclear bodies and reorganize the genome.
Collapse
Affiliation(s)
- Jing Xu
- School of Life Science, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Xiaolu Zhao
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Fengbiao Mao
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Venkatesha Basrur
- Proteomics Resource Facility, Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Beatrix Ueberheide
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, the Rockefeller University, New York, NY 10065, USA
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, the Rockefeller University, New York, NY 10065, USA
| | - C David Allis
- Laboratory of Chromatin Biology and Epigenetics, the Rockefeller University, New York, NY 10065, USA
| | - Sean D Taverna
- Department of Pharmacology and Molecular Sciences and the Center for Epigenetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Shan Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Wei Wang
- School of Life Science, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Yifan Liu
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| |
Collapse
|
57
|
Guo Y, Zhao S, Wang GG. Polycomb Gene Silencing Mechanisms: PRC2 Chromatin Targeting, H3K27me3 'Readout', and Phase Separation-Based Compaction. Trends Genet 2021; 37:547-565. [PMID: 33494958 PMCID: PMC8119337 DOI: 10.1016/j.tig.2020.12.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 12/18/2020] [Accepted: 12/22/2020] [Indexed: 12/20/2022]
Abstract
Modulation of chromatin structure and/or modification by Polycomb repressive complexes (PRCs) provides an important means to partition the genome into functionally distinct subdomains and to regulate the activity of the underlying genes. Both the enzymatic activity of PRC2 and its chromatin recruitment, spreading, and eviction are exquisitely regulated via interactions with cofactors and DNA elements (such as unmethylated CpG islands), histones, RNA (nascent mRNA and long noncoding RNA), and R-loops. PRC2-catalyzed histone H3 lysine 27 trimethylation (H3K27me3) is recognized by distinct classes of effectors such as canonical PRC1 and BAH module-containing proteins (notably BAHCC1 in human). These effectors mediate gene silencing by different mechanisms including phase separation-related chromatin compaction and histone deacetylation. We discuss recent advances in understanding the structural architecture of PRC2, the regulation of its activity and chromatin recruitment, and the molecular mechanisms underlying Polycomb-mediated gene silencing. Because PRC deregulation is intimately associated with the development of diseases, a better appreciation of Polycomb-based (epi)genomic regulation will have far-reaching implications in biology and medicine.
Collapse
Affiliation(s)
- Yiran Guo
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA; Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Shuai Zhao
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Gang Greg Wang
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA; Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA.
| |
Collapse
|
58
|
Su D, Wang W, Hou Y, Wang L, Yi X, Cao C, Wang Y, Gao H, Wang Y, Yang C, Liu B, Chen X, Wu X, Wu J, Yan D, Wei S, Han L, Liu S, Wang Q, Shi L, Shan L. Bimodal regulation of the PRC2 complex by USP7 underlies tumorigenesis. Nucleic Acids Res 2021; 49:4421-4440. [PMID: 33849069 PMCID: PMC8096222 DOI: 10.1093/nar/gkab209] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/01/2021] [Indexed: 12/27/2022] Open
Abstract
Although overexpression of EZH2, a catalytic subunit of the polycomb repressive complex 2 (PRC2), is an eminent feature of various cancers, the regulation of its abundance and function remains insufficiently understood. We report here that the PRC2 complex is physically associated with ubiquitin-specific protease USP7 in cancer cells where USP7 acts to deubiquitinate and stabilize EZH2. Interestingly, we found that USP7-catalyzed H2BK120ub1 deubiquitination is a prerequisite for chromatin loading of PRC2 thus H3K27 trimethylation, and this process is not affected by H2AK119 ubiquitination catalyzed by PRC1. Genome-wide analysis of the transcriptional targets of the USP7/PRC2 complex identified a cohort of genes including FOXO1 that are involved in cell growth and proliferation. We demonstrated that the USP7/PRC2 complex drives cancer cell proliferation and tumorigenesis in vitro and in vivo. We showed that the expression of both USP7 and EZH2 elevates during tumor progression, corresponding to a diminished FOXO1 expression, and the level of the expression of USP7 and EZH2 strongly correlates with histological grades and prognosis of tumor patients. These results reveal a dual role for USP7 in the regulation of the abundance and function of EZH2, supporting the pursuit of USP7 as a therapeutic target for cancer intervention.
Collapse
Affiliation(s)
- Dongxue Su
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China.,State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Wenjuan Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Yongqiang Hou
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China.,Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Liyong Wang
- Core Facilities for Molecular Biology, Capital Medical University, Beijing 100069, China
| | - Xianfu Yi
- School of Biomedical Engineering, Tianjin Medical University, Tianjin 300070, China
| | - Cheng Cao
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Yuejiao Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Huan Gao
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Yue Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Chao Yang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Beibei Liu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Xing Chen
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Xiaodi Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Jiajing Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Dong Yan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Shuqi Wei
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Lulu Han
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Shumeng Liu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Qian Wang
- Tianjin Medical University Cancer Institute and Hospital, Tianjin Key Laboratory of Cancer Prevention and Therapy, National Clinical Research Center for Cancer, Tianjin 300060, China
| | - Lei Shi
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Lin Shan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| |
Collapse
|
59
|
Vodnala M, Choi EB, Fong YW. Low complexity domains, condensates, and stem cell pluripotency. World J Stem Cells 2021; 13:416-438. [PMID: 34136073 PMCID: PMC8176841 DOI: 10.4252/wjsc.v13.i5.416] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 04/20/2021] [Accepted: 04/28/2021] [Indexed: 02/06/2023] Open
Abstract
Biological reactions require self-assembly of factors in the complex cellular milieu. Recent evidence indicates that intrinsically disordered, low-complexity sequence domains (LCDs) found in regulatory factors mediate diverse cellular processes from gene expression to DNA repair to signal transduction, by enriching specific biomolecules in membraneless compartments or hubs that may undergo liquid-liquid phase separation (LLPS). In this review, we discuss how embryonic stem cells take advantage of LCD-driven interactions to promote cell-specific transcription, DNA damage response, and DNA repair. We propose that LCD-mediated interactions play key roles in stem cell maintenance and safeguarding genome integrity.
Collapse
Affiliation(s)
- Munender Vodnala
- Department of Medicine, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Eun-Bee Choi
- Department of Medicine, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Yick W Fong
- Department of Medicine, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
- Harvard Stem Cell Institute, Cambridge, MA 02138, United States.
| |
Collapse
|
60
|
Sidwell T, Rothenberg EV. Epigenetic Dynamics in the Function of T-Lineage Regulatory Factor Bcl11b. Front Immunol 2021; 12:669498. [PMID: 33936112 PMCID: PMC8079813 DOI: 10.3389/fimmu.2021.669498] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 03/23/2021] [Indexed: 11/18/2022] Open
Abstract
The transcription factor Bcl11b is critically required to support the development of diverse cell types, including T lymphocytes, type 2 innate lymphoid cells, neurons, craniofacial mesenchyme and keratinocytes. Although in T cell development its onset of expression is tightly linked to T-lymphoid lineage commitment, the Bcl11b protein in fact regulates substantially different sets of genes in different lymphocyte populations, playing strongly context-dependent roles. Somewhat unusually for lineage-defining transcription factors with site-specific DNA binding activity, much of the reported chromatin binding of Bcl11b appears to be indirect, or guided in large part by interactions with other transcription factors. We describe evidence suggesting that a further way in which Bcl11b exerts such distinct stage-dependent functions is by nucleating changes in regional suites of epigenetic modifications through recruitment of multiple families of chromatin-modifying enzyme complexes. Herein we explore what is - and what remains to be - understood of the roles of Bcl11b, its cofactors, and how it modifies the epigenetic state of the cell to enforce its diverse set of context-specific transcriptional and developmental programs.
Collapse
Affiliation(s)
- Tom Sidwell
- Division of Biology & Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - Ellen V Rothenberg
- Division of Biology & Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| |
Collapse
|
61
|
Baumann C, Zhang X, De La Fuente R. Loss of CBX2 induces genome instability and senescence-associated chromosomal rearrangements. J Cell Biol 2021; 219:152063. [PMID: 32870972 PMCID: PMC7594495 DOI: 10.1083/jcb.201910149] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 06/08/2020] [Accepted: 08/02/2020] [Indexed: 01/05/2023] Open
Abstract
The polycomb group protein CBX2 is an important epigenetic reader involved in cell proliferation and differentiation. While CBX2 overexpression occurs in a wide range of human tumors, targeted deletion results in homeotic transformation, proliferative defects, and premature senescence. However, its cellular function(s) and whether it plays a role in maintenance of genome stability remain to be determined. Here, we demonstrate that loss of CBX2 in mouse fibroblasts induces abnormal large-scale chromatin structure and chromosome instability. Integrative transcriptome analysis and ATAC-seq revealed a significant dysregulation of transcripts involved in DNA repair, chromocenter formation, and tumorigenesis in addition to changes in chromatin accessibility of genes involved in lateral sclerosis, basal transcription factors, and folate metabolism. Notably, Cbx2−/− cells exhibit prominent decondensation of satellite DNA sequences at metaphase and increased sister chromatid recombination events leading to rampant chromosome instability. The presence of extensive centromere and telomere defects suggests a prominent role for CBX2 in heterochromatin homeostasis and the regulation of nuclear architecture.
Collapse
Affiliation(s)
- Claudia Baumann
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA.,Regenerative Bioscience Center, University of Georgia, Athens, GA
| | - Xiangyu Zhang
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA.,Regenerative Bioscience Center, University of Georgia, Athens, GA
| | - Rabindranath De La Fuente
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA.,Regenerative Bioscience Center, University of Georgia, Athens, GA
| |
Collapse
|
62
|
Huseyin MK, Klose RJ. Live-cell single particle tracking of PRC1 reveals a highly dynamic system with low target site occupancy. Nat Commun 2021; 12:887. [PMID: 33563969 PMCID: PMC7873255 DOI: 10.1038/s41467-021-21130-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Accepted: 01/13/2021] [Indexed: 01/04/2023] Open
Abstract
Polycomb repressive complex 1 (PRC1) is an essential chromatin-based repressor of gene transcription. How PRC1 engages with chromatin to identify its target genes and achieve gene repression remains poorly defined, representing a major hurdle to our understanding of Polycomb system function. Here, we use genome engineering and single particle tracking to dissect how PRC1 binds to chromatin in live mouse embryonic stem cells. We observe that PRC1 is highly dynamic, with only a small fraction stably interacting with chromatin. By integrating subunit-specific dynamics, chromatin binding, and abundance measurements, we discover that PRC1 exhibits low occupancy at target sites. Furthermore, we employ perturbation approaches to uncover how specific components of PRC1 define its kinetics and chromatin binding. Together, these discoveries provide a quantitative understanding of chromatin binding by PRC1 in live cells, suggesting that chromatin modification, as opposed to PRC1 complex occupancy, is central to gene repression.
Collapse
Affiliation(s)
- Miles K Huseyin
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Robert J Klose
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
| |
Collapse
|
63
|
van Wijnen AJ, Bagheri L, Badreldin AA, Larson AN, Dudakovic A, Thaler R, Paradise CR, Wu Z. Biological functions of chromobox (CBX) proteins in stem cell self-renewal, lineage-commitment, cancer and development. Bone 2021; 143:115659. [PMID: 32979540 DOI: 10.1016/j.bone.2020.115659] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 09/02/2020] [Accepted: 09/21/2020] [Indexed: 02/06/2023]
Abstract
Epigenetic regulatory proteins support mammalian development, cancer, aging and tissue repair by controlling many cellular processes including stem cell self-renewal, lineage-commitment and senescence in both skeletal and non-skeletal tissues. We review here our knowledge of epigenetic regulatory protein complexes that support the formation of inaccessible heterochromatin and suppress expression of cell and tissue-type specific biomarkers during development. Maintenance and formation of heterochromatin critically depends on epigenetic regulators that recognize histone 3 lysine trimethylation at residues K9 and K27 (respectively, H3K9me3 and H3K27me3), which represent transcriptionally suppressive epigenetic marks. Three chromobox proteins (i.e., CBX1, CBX3 or CBX5) associated with the heterochromatin protein 1 (HP1) complex are methyl readers that interpret H3K9me3 marks which are mediated by H3K9 methyltransferases (i.e., SUV39H1 or SUV39H2). Other chromobox proteins (i.e., CBX2, CBX4, CBX6, CBX7 and CBX8) recognize H3K27me3, which is deposited by Polycomb Repressive Complex 2 (PRC2; a complex containing SUZ12, EED, RBAP46/48 and the methyl transferases EZH1 or EZH2). This second set of CBX proteins resides in PRC1, which has many subunits including other polycomb group factors (PCGF1, PCGF2, PCGF3, PCGF4, PCGF5, PCGF6), human polyhomeotic homologs (HPH1, HPH2, HPH3) and E3-ubiquitin ligases (RING1 or RING2). The latter enzymes catalyze the subsequent mono-ubiquitination of lysine 119 in H2A (H2AK119ub). We discuss biological, cellular and molecular functions of CBX proteins and their physiological and pathological activities in non-skeletal cells and tissues in anticipation of new discoveries on novel roles for CBX proteins in bone formation and skeletal development.
Collapse
Affiliation(s)
- Andre J van Wijnen
- Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America; Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America; Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, United States of America.
| | - Leila Bagheri
- Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America.
| | - Amr A Badreldin
- Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America.
| | - A Noelle Larson
- Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America.
| | - Amel Dudakovic
- Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America; Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America.
| | - Roman Thaler
- Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America.
| | - Christopher R Paradise
- Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, United States of America; Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, United States of America
| | - Zhong Wu
- Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, United States of America
| |
Collapse
|
64
|
Grau D, Zhang Y, Lee CH, Valencia-Sánchez M, Zhang J, Wang M, Holder M, Svetlov V, Tan D, Nudler E, Reinberg D, Walz T, Armache KJ. Structures of monomeric and dimeric PRC2:EZH1 reveal flexible modules involved in chromatin compaction. Nat Commun 2021; 12:714. [PMID: 33514705 PMCID: PMC7846606 DOI: 10.1038/s41467-020-20775-z] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 12/18/2020] [Indexed: 01/02/2023] Open
Abstract
Polycomb repressive complex 2 (PRC2) is a histone methyltransferase critical for maintaining gene silencing during eukaryotic development. In mammals, PRC2 activity is regulated in part by the selective incorporation of one of two paralogs of the catalytic subunit, EZH1 or EZH2. Each of these enzymes has specialized biological functions that may be partially explained by differences in the multivalent interactions they mediate with chromatin. Here, we present two cryo-EM structures of PRC2:EZH1, one as a monomer and a second one as a dimer bound to a nucleosome. When bound to nucleosome substrate, the PRC2:EZH1 dimer undergoes a dramatic conformational change. We demonstrate that mutation of a divergent EZH1/2 loop abrogates the nucleosome-binding and methyltransferase activities of PRC2:EZH1. Finally, we show that PRC2:EZH1 dimers are more effective than monomers at promoting chromatin compaction, and the divergent EZH1/2 loop is essential for this function, thereby tying together the methyltransferase, nucleosome-binding, and chromatin-compaction activities of PRC2:EZH1. We speculate that the conformational flexibility and the ability to dimerize enable PRC2 to act on the varied chromatin substrates it encounters in the cell. Polycomb Repressive Complex 2 (PRC2) is a histone methyltransferase whose silencing activity is regulated in part by the selective incorporation of its catalytic subunits EZH1 or EZH2. Here, the authors capture an EZH1-containing PRC2 dimer on a nucleosome, demonstrating significant conformational changes during the process.
Collapse
Affiliation(s)
- Daniel Grau
- Skirball Institute of Biomolecular Medicine, Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Yixiao Zhang
- Laboratory of Molecular Electron Microscopy, The Rockefeller University, New York, NY, USA
| | - Chul-Hwan Lee
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA.,Department of Pharmacology, Seoul National University, Seoul, Republic of Korea
| | - Marco Valencia-Sánchez
- Skirball Institute of Biomolecular Medicine, Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Jenny Zhang
- Skirball Institute of Biomolecular Medicine, Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Miao Wang
- Skirball Institute of Biomolecular Medicine, Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Marlene Holder
- Skirball Institute of Biomolecular Medicine, Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Vladimir Svetlov
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Dongyan Tan
- Department of Pharmacological Sciences, Stony Brook University Medical School, Stony Brook, NY, USA
| | - Evgeny Nudler
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Danny Reinberg
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Thomas Walz
- Laboratory of Molecular Electron Microscopy, The Rockefeller University, New York, NY, USA.
| | - Karim-Jean Armache
- Skirball Institute of Biomolecular Medicine, Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.
| |
Collapse
|
65
|
Genetische Grundlagen bei Varianten der Geschlechtsentwicklung. GYNAKOLOGISCHE ENDOKRINOLOGIE 2020. [DOI: 10.1007/s10304-020-00359-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
66
|
Structural basis for PRC2 engagement with chromatin. Curr Opin Struct Biol 2020; 67:135-144. [PMID: 33232890 DOI: 10.1016/j.sbi.2020.10.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 10/14/2020] [Accepted: 10/19/2020] [Indexed: 02/08/2023]
Abstract
The polycomb repressive complex 2 (PRC2) is a conserved multiprotein, repressive chromatin complex essential for development and maintenance of eukaryotic cellular identity. PRC2 comprises a trimeric core of SUZ12, EED and EZH1/2, which together with RBBP4/7 is sufficient to catalyse mono-methylation, di-methylation and tri-methylation of histone H3 at lysine 27 (H3K27me1/2/3). These histone methyltransferase activities of PRC2 are deregulated in several human cancers and certain developmental disorders, such as Weaver Syndrome. Core PRC2 associates with several accessory proteins, which organise to define two main subassemblies, PRC2.1 and PRC2.2. Here we review new biochemical and structural studies that are providing critical insights into how core and accessory PRC2 subunits coordinate the faithful deposition of H3K27 methylations genome-wide.
Collapse
|
67
|
Geng Z, Gao Z. Mammalian PRC1 Complexes: Compositional Complexity and Diverse Molecular Mechanisms. Int J Mol Sci 2020; 21:E8594. [PMID: 33202645 PMCID: PMC7697839 DOI: 10.3390/ijms21228594] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 11/04/2020] [Accepted: 11/05/2020] [Indexed: 12/13/2022] Open
Abstract
Polycomb group (PcG) proteins function as vital epigenetic regulators in various biological processes, including pluripotency, development, and carcinogenesis. PcG proteins form multicomponent complexes, and two major types of protein complexes have been identified in mammals to date, Polycomb Repressive Complexes 1 and 2 (PRC1 and PRC2). The PRC1 complexes are composed in a hierarchical manner in which the catalytic core, RING1A/B, exclusively interacts with one of six Polycomb group RING finger (PCGF) proteins. This association with specific PCGF proteins allows for PRC1 to be subdivided into six distinct groups, each with their own unique modes of action arising from the distinct set of associated proteins. Historically, PRC1 was considered to be a transcription repressor that deposited monoubiquitylation of histone H2A at lysine 119 (H2AK119ub1) and compacted local chromatin. More recently, there is increasing evidence that demonstrates the transcription activation role of PRC1. Moreover, studies on the higher-order chromatin structure have revealed a new function for PRC1 in mediating long-range interactions. This provides a different perspective regarding both the transcription activation and repression characteristics of PRC1. This review summarizes new advancements regarding the composition of mammalian PRC1 and accompanying explanations of how diverse PRC1-associated proteins participate in distinct transcription regulation mechanisms.
Collapse
Affiliation(s)
- Zhuangzhuang Geng
- Departments of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, PA 17033, USA;
| | - Zhonghua Gao
- Departments of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, PA 17033, USA;
- Penn State Hershey Cancer Institute, Hershey, PA 17033, USA
- The Stem Cell and Regenerative Biology Program, Penn State College of Medicine, Hershey, PA 17033, USA
| |
Collapse
|
68
|
Phillips RE, Soshnev AA, Allis CD. Epigenomic Reprogramming as a Driver of Malignant Glioma. Cancer Cell 2020; 38:647-660. [PMID: 32916125 PMCID: PMC8248764 DOI: 10.1016/j.ccell.2020.08.008] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/21/2020] [Accepted: 08/10/2020] [Indexed: 12/13/2022]
Abstract
Malignant gliomas are central nervous system tumors and remain among the most treatment-resistant cancers. Exome sequencing has revealed significant heterogeneity and important insights into the molecular pathogenesis of gliomas. Mutations in chromatin modifiers-proteins that shape the epigenomic landscape through remodeling and regulation of post-translational modifications on chromatin-are very frequent and often define specific glioma subtypes. This suggests that epigenomic reprogramming may be a fundamental driver of glioma. Here, we describe the key chromatin regulatory pathways disrupted in gliomas, delineating their physiological function and our current understanding of how their dysregulation may contribute to gliomagenesis.
Collapse
Affiliation(s)
- Richard E Phillips
- Department of Neurology and Brain Tumor Center, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Laboratory of Chromatin Biology and Epigenetics, The Rockefeller University, New York, NY 10065, USA.
| | - Alexey A Soshnev
- Laboratory of Chromatin Biology and Epigenetics, The Rockefeller University, New York, NY 10065, USA
| | - C David Allis
- Laboratory of Chromatin Biology and Epigenetics, The Rockefeller University, New York, NY 10065, USA.
| |
Collapse
|
69
|
Seif E, Kang JJ, Sasseville C, Senkovich O, Kaltashov A, Boulier EL, Kapur I, Kim CA, Francis NJ. Phase separation by the polyhomeotic sterile alpha motif compartmentalizes Polycomb Group proteins and enhances their activity. Nat Commun 2020; 11:5609. [PMID: 33154383 PMCID: PMC7644731 DOI: 10.1038/s41467-020-19435-z] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 10/08/2020] [Indexed: 02/07/2023] Open
Abstract
Polycomb Group (PcG) proteins organize chromatin at multiple scales to regulate gene expression. A conserved Sterile Alpha Motif (SAM) in the Polycomb Repressive Complex 1 (PRC1) subunit Polyhomeotic (Ph) has been shown to play an important role in chromatin compaction and large-scale chromatin organization. Ph SAM forms helical head to tail polymers, and SAM-SAM interactions between chromatin-bound Ph/PRC1 are believed to compact chromatin and mediate long-range interactions. To understand the underlying mechanism, here we analyze the effects of Ph SAM on chromatin in vitro. We find that incubation of chromatin or DNA with a truncated Ph protein containing the SAM results in formation of concentrated, phase-separated condensates. Ph SAM-dependent condensates can recruit PRC1 from extracts and enhance PRC1 ubiquitin ligase activity towards histone H2A. We show that overexpression of Ph with an intact SAM increases ubiquitylated H2A in cells. Thus, SAM-induced phase separation, in the context of Ph, can mediate large-scale compaction of chromatin into biochemical compartments that facilitate histone modification.
Collapse
Affiliation(s)
- Elias Seif
- Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC, H2W 1R7, Canada
| | - Jin Joo Kang
- Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC, H2W 1R7, Canada
- Division of Experimental Medicine, McGill University, 1001 Decarie Boulevard, Montreal, QC, H4A 3J1, Canada
| | - Charles Sasseville
- Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC, H2W 1R7, Canada
| | - Olga Senkovich
- Department of Biochemistry and Molecular Genetics, Midwestern University, 19555N. 59th St., Glendale, AZ, 85308, USA
| | - Alexander Kaltashov
- Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC, H2W 1R7, Canada
| | - Elodie L Boulier
- Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC, H2W 1R7, Canada
| | - Ibani Kapur
- Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC, H2W 1R7, Canada
- Division of Experimental Medicine, McGill University, 1001 Decarie Boulevard, Montreal, QC, H4A 3J1, Canada
| | - Chongwoo A Kim
- Department of Biochemistry and Molecular Genetics, Midwestern University, 19555N. 59th St., Glendale, AZ, 85308, USA
| | - Nicole J Francis
- Institut de recherches cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC, H2W 1R7, Canada.
- Division of Experimental Medicine, McGill University, 1001 Decarie Boulevard, Montreal, QC, H4A 3J1, Canada.
- Département de biochimie et médecine moléculaire Université de Montréal, 2900 Boulevard Edouard-Montpetit, Montréal, QC, H3T 1J4, Canada.
| |
Collapse
|
70
|
Kent S, Brown K, Yang CH, Alsaihati N, Tian C, Wang H, Ren X. Phase-Separated Transcriptional Condensates Accelerate Target-Search Process Revealed by Live-Cell Single-Molecule Imaging. Cell Rep 2020; 33:108248. [PMID: 33053359 PMCID: PMC7593837 DOI: 10.1016/j.celrep.2020.108248] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 08/07/2020] [Accepted: 09/17/2020] [Indexed: 12/11/2022] Open
Abstract
Compartmentalization by liquid-liquid phase separation is implicated in transcription. It remains unclear whether and how transcriptional condensates accelerate the search of transcriptional regulatory factors for their target sites. Furthermore, the molecular mechanisms by which regulatory factors nucleate on chromatin to assemble transcriptional condensates remain incompletely understood. The CBX-PRC1 complexes compartmentalize key developmental regulators for repression through phase-separated condensates driven by the chromobox 2 (CBX2) protein. Here, by using live-cell single-molecule imaging, we show that CBX2 nucleates on chromatin independently of H3K27me3 and CBX-PRC1. The interactions between CBX2 and DNA are essential for nucleating CBX-PRC1 on chromatin to assemble condensates. The assembled condensates shorten 3D diffusion time and reduce trials for finding specific sites through revisiting the same or adjacent sites repetitively, thereby accelerating CBX2 in searching for target sites. Overall, our data suggest a generic mechanism by which transcriptional regulatory factors nucleate to assemble condensates that accelerate their target-search process. Kent et al. demonstrate that CBX2 phase separates to assemble Polycomb condensates on chromatin through CBX2 interactions with DNA rather than H3K27me3. The assembled condensates accelerate the search of CBX2 for its cognate binding sites by revisiting the same or adjacent sites repetitively, thereby enhancing the genomic occupancy of CBX2.
Collapse
Affiliation(s)
- Samantha Kent
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Kyle Brown
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Chou-Hsun Yang
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Njood Alsaihati
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Christina Tian
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Haobin Wang
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Xiaojun Ren
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364, USA.
| |
Collapse
|
71
|
Abstract
Regeneration is the process by which organisms replace lost or damaged tissue, and regenerative capacity can vary greatly among species, tissues and life stages. Tissue regeneration shares certain hallmarks of embryonic development, in that lineage-specific factors can be repurposed upon injury to initiate morphogenesis; however, many differences exist between regeneration and embryogenesis. Recent studies of regenerating tissues in laboratory model organisms - such as acoel worms, frogs, fish and mice - have revealed that chromatin structure, dedicated enhancers and transcriptional networks are regulated in a context-specific manner to control key gene expression programmes. A deeper mechanistic understanding of the gene regulatory networks of regeneration pathways might ultimately enable their targeted reactivation as a means to treat human injuries and degenerative diseases. In this Review, we consider the regeneration of body parts across a range of tissues and species to explore common themes and potentially exploitable elements.
Collapse
Affiliation(s)
- Joseph A Goldman
- Department of Biological Chemistry and Pharmacology, Ohio State University, Columbus, OH, USA.
| | - Kenneth D Poss
- Regeneration Next, Duke University, Durham, NC, USA.
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA.
| |
Collapse
|
72
|
The genetic basis for PRC1 complex diversity emerged early in animal evolution. Proc Natl Acad Sci U S A 2020; 117:22880-22889. [PMID: 32868440 DOI: 10.1073/pnas.2005136117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Polycomb group proteins are essential regulators of developmental processes across animals. Despite their importance, studies on Polycomb are often restricted to classical model systems and, as such, little is known about the evolution of these important chromatin regulators. Here we focus on Polycomb Repressive Complex 1 (PRC1) and trace the evolution of core components of canonical and non-canonical PRC1 complexes in animals. Previous work suggested that a major expansion in the number of PRC1 complexes occurred in the vertebrate lineage. We show that the expansion of the Polycomb Group RING Finger (PCGF) protein family, an essential step for the establishment of the large diversity of PRC1 complexes found in vertebrates, predates the bilaterian-cnidarian ancestor. This means that the genetic repertoire necessary to form all major vertebrate PRC1 complexes emerged early in animal evolution, over 550 million years ago. We further show that PCGF5, a gene conserved in cnidarians and vertebrates but lost in all other studied groups, is expressed in the nervous system in the sea anemone Nematostella vectensis, similar to its mammalian counterpart. Together this work provides a framework for understanding the evolution of PRC1 complex diversity and it establishes Nematostella as a promising model system in which the functional ramifications of this diversification can be further explored.
Collapse
|
73
|
Giner-Laguarda N, Vidal M. Functions of Polycomb Proteins on Active Targets. EPIGENOMES 2020; 4:17. [PMID: 34968290 PMCID: PMC8594714 DOI: 10.3390/epigenomes4030017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 08/12/2020] [Accepted: 08/13/2020] [Indexed: 12/15/2022] Open
Abstract
Chromatin regulators of the Polycomb group of genes are well-known by their activities as transcriptional repressors. Characteristically, their presence at genomic sites occurs with specific histone modifications and sometimes high-order chromatin structures correlated with silencing of genes involved in cell differentiation. However, evidence gathered in recent years, on flies and mammals, shows that in addition to these sites, Polycomb products bind to a large number of active regulatory regions. Occupied sites include promoters and also intergenic regions, containing enhancers and super-enhancers. Contrasting with occupancies at repressed targets, characteristic histone modifications are low or undetectable. Functions on active targets are dual, restraining gene expression at some targets while promoting activity at others. Our aim here is to summarize the evidence available and discuss the convenience of broadening the scope of research to include Polycomb functions on active targets.
Collapse
Affiliation(s)
| | - Miguel Vidal
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas Margarita Salas, Ramiro de Maeztu 9, 28040 Madrid, Spain;
| |
Collapse
|
74
|
Perino M, van Mierlo G, Loh C, Wardle SMT, Zijlmans DW, Marks H, Veenstra GJC. Two Functional Axes of Feedback-Enforced PRC2 Recruitment in Mouse Embryonic Stem Cells. Stem Cell Reports 2020; 15:1287-1300. [PMID: 32763159 PMCID: PMC7724473 DOI: 10.1016/j.stemcr.2020.07.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 07/07/2020] [Accepted: 07/08/2020] [Indexed: 12/22/2022] Open
Abstract
Polycomb Repressive Complex 2 (PRC2) plays an essential role in gene repression during development, catalyzing H3 lysine 27 trimethylation (H3K27me3). MTF2 in the PRC2.1 sub-complex, and JARID2 in PRC2.2, are central in core PRC2 recruitment to target genes in mouse embryonic stem cells (mESCs). To investigate how PRC2.1 and PRC2.2 cooperate, we combined Polycomb mutant mESCs with chemical inhibition of binding to H3K27me3. We find that PRC2.1 and PRC2.2 mediate two distinct paths for recruitment, which are mutually reinforced. Whereas PRC2.1 recruitment is mediated by MTF2 binding to DNA, JARID2-containing PRC2.2 recruitment is more dependent on PRC1. Both recruitment axes are supported by core subunit EED binding to H3K27me3, but EED inhibition exhibits a more pronounced effect in Jarid2 null cells. Finally, we show that PRC1 and PRC2 enhance reciprocal binding. Together, these data disentangle the interdependent interactions that are important for PRC2 recruitment.
Collapse
Affiliation(s)
- Matteo Perino
- Department of Molecular Developmental Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, the Netherlands
| | - Guido van Mierlo
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, the Netherlands
| | - Chet Loh
- Department of Molecular Developmental Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, the Netherlands
| | - Sandra M T Wardle
- Department of Molecular Developmental Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, the Netherlands
| | - Dick W Zijlmans
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, the Netherlands
| | - Hendrik Marks
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, the Netherlands.
| | - Gert Jan C Veenstra
- Department of Molecular Developmental Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, the Netherlands.
| |
Collapse
|
75
|
Boyle S, Flyamer IM, Williamson I, Sengupta D, Bickmore WA, Illingworth RS. A central role for canonical PRC1 in shaping the 3D nuclear landscape. Genes Dev 2020; 34:931-949. [PMID: 32439634 PMCID: PMC7328521 DOI: 10.1101/gad.336487.120] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 04/13/2020] [Indexed: 02/04/2023]
Abstract
In this study from Boyle et al., the authors investigated the role of Polycomb-repressive complex 1 (PRC1) in shaping 3D genome organization in mouse embryonic stem cells. Using a combination of imaging and Hi-C analyses they show that PRC1-mediated long-range interactions are independent of CTCF and can bridge sites at a megabase scale, thus providing novel insights into the function of PRC1. Polycomb group (PcG) proteins silence gene expression by chemically and physically modifying chromatin. A subset of PcG target loci are compacted and cluster in the nucleus; a conformation that is thought to contribute to gene silencing. However, how these interactions influence gross nuclear organization and their relationship with transcription remains poorly understood. Here we examine the role of Polycomb-repressive complex 1 (PRC1) in shaping 3D genome organization in mouse embryonic stem cells (mESCs). Using a combination of imaging and Hi-C analyses, we show that PRC1-mediated long-range interactions are independent of CTCF and can bridge sites at a megabase scale. Impairment of PRC1 enzymatic activity does not directly disrupt these interactions. We demonstrate that PcG targets coalesce in vivo, and that developmentally induced expression of one of the target loci disrupts this spatial arrangement. Finally, we show that transcriptional activation and the loss of PRC1-mediated interactions are separable events. These findings provide important insights into the function of PRC1, while highlighting the complexity of this regulatory system.
Collapse
Affiliation(s)
- Shelagh Boyle
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Ilya M Flyamer
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Iain Williamson
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Dipta Sengupta
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Wendy A Bickmore
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Robert S Illingworth
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| |
Collapse
|
76
|
Pachano T, Crispatzu G, Rada-Iglesias A. Polycomb proteins as organizers of 3D genome architecture in embryonic stem cells. Brief Funct Genomics 2020; 18:358-366. [PMID: 31673701 DOI: 10.1093/bfgp/elz022] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Revised: 08/14/2019] [Accepted: 08/22/2019] [Indexed: 12/29/2022] Open
Abstract
Polycomb group proteins (PcGs) control the epigenetic and transcriptional state of developmental genes and regulatory elements during mammalian embryogenesis. Moreover, PcGs can also contribute to 3D genome organization, adding an additional layer of complexity to their regulatory functions. Understanding the mechanistic basis and the dynamics of PcG-dependent chromatin structures will help us untangle the full complexity of PcG function during development. Since most studies concerning the 3D organization of PcG-bound chromatin in mammals have been performed in embryonic stem cells (ESCs), here we will focus on this cell type characterized by its unique self-renewal and pluripotency properties. More specifically, we will highlight recent findings and discuss open questions regarding how PcG-dependent changes in 3D chromatin architecture control gene expression, cellular identity and differentiation potential in ESCs. We believe that this can serve to illustrate the diverse regulatory mechanisms by which PcG proteins control the proper execution of gene expression programs during mammalian embryogenesis.
Collapse
Affiliation(s)
- Tomas Pachano
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Germany
| | - Giuliano Crispatzu
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Germany.,Department II of Internal Medicine, University Hospital Cologne, Germany
| | - Alvaro Rada-Iglesias
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Germany.,Cluster of Excellence Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany.,Institute of Biomedicine and Biotechnology of Cantabria (IBBTEC), University of Cantabria, Spain
| |
Collapse
|
77
|
Liu Z, Tardat M, Gill ME, Royo H, Thierry R, Ozonov EA, Peters AH. SUMOylated PRC1 controls histone H3.3 deposition and genome integrity of embryonic heterochromatin. EMBO J 2020; 39:e103697. [PMID: 32395866 PMCID: PMC7327501 DOI: 10.15252/embj.2019103697] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 04/09/2020] [Accepted: 04/14/2020] [Indexed: 12/14/2022] Open
Abstract
Chromatin integrity is essential for cellular homeostasis. Polycomb group proteins modulate chromatin states and transcriptionally repress developmental genes to maintain cell identity. They also repress repetitive sequences such as major satellites and constitute an alternative state of pericentromeric constitutive heterochromatin at paternal chromosomes (pat‐PCH) in mouse pre‐implantation embryos. Remarkably, pat‐PCH contains the histone H3.3 variant, which is absent from canonical PCH at maternal chromosomes, which is marked by histone H3 lysine 9 trimethylation (H3K9me3), HP1, and ATRX proteins. Here, we show that SUMO2‐modified CBX2‐containing Polycomb Repressive Complex 1 (PRC1) recruits the H3.3‐specific chaperone DAXX to pat‐PCH, enabling H3.3 incorporation at these loci. Deficiency of Daxx or PRC1 components Ring1 and Rnf2 abrogates H3.3 incorporation, induces chromatin decompaction and breakage at PCH of exclusively paternal chromosomes, and causes their mis‐segregation. Complementation assays show that DAXX‐mediated H3.3 deposition is required for chromosome stability in early embryos. DAXX also regulates repression of PRC1 target genes during oogenesis and early embryogenesis. The study identifies a novel critical role for Polycomb in ensuring heterochromatin integrity and chromosome stability in mouse early development.
Collapse
Affiliation(s)
- Zichuan Liu
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Mathieu Tardat
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Mark E Gill
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Helene Royo
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Raphael Thierry
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Evgeniy A Ozonov
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Antoine Hfm Peters
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.,Faculty of Sciences, University of Basel, Basel, Switzerland
| |
Collapse
|
78
|
Cohen I, Bar C, Ezhkova E. Activity of PRC1 and Histone H2AK119 Monoubiquitination: Revising Popular Misconceptions. Bioessays 2020; 42:e1900192. [PMID: 32196702 PMCID: PMC7585675 DOI: 10.1002/bies.201900192] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 02/12/2020] [Indexed: 12/21/2022]
Abstract
Polycomb group proteins are evolutionary conserved chromatin-modifying complexes, essential for the regulation of developmental and cell-identity genes. Polycomb-mediated transcriptional regulation is provided by two multi-protein complexes known as Polycomb repressive complex 1 (PRC1) and 2 (PRC2). Recent studies positioned PRC1 as a foremost executer of Polycomb-mediated transcriptional control. Mammalian PRC1 complexes can form multiple sub-complexes that vary in their core and accessory subunit composition, leading to fascinating and diverse transcriptional regulatory mechanisms employed by PRC1 complexes. These mechanisms include PRC1-catalytic activity toward monoubiquitination of histone H2AK119, a well-established hallmark of PRC1 complexes, whose importance has been long debated. In this review, the central roles that PRC1-catalytic activity plays in transcriptional repression are emphasized and the recent evidence supporting a role for PRC1 complexes in gene activation is discussed.
Collapse
Affiliation(s)
- Idan Cohen
- The Shraga Segal Department of Microbiology, Immunology and Genetics; Faculty of Health Science; Ben-Gurion University of the Negev; Beer Sheva 84105; Israel
- These authors contributed equally to this work
| | - Carmit Bar
- Black Family Stem Cell Institute, Department of Cell, Developmental, and Regenerative Biology; Icahn School of Medicine at Mount Sinai; 1 Gustave L. Levy Place, New York, NY 10029; USA
- These authors contributed equally to this work
| | - Elena Ezhkova
- The Shraga Segal Department of Microbiology, Immunology and Genetics; Faculty of Health Science; Ben-Gurion University of the Negev; Beer Sheva 84105; Israel
| |
Collapse
|
79
|
Dunican DS, Mjoseng HK, Duthie L, Flyamer IM, Bickmore WA, Meehan RR. Bivalent promoter hypermethylation in cancer is linked to the H327me3/H3K4me3 ratio in embryonic stem cells. BMC Biol 2020; 18:25. [PMID: 32131813 PMCID: PMC7057567 DOI: 10.1186/s12915-020-0752-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 02/14/2020] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Thousands of mammalian promoters are defined by co-enrichment of the histone tail modifications H3K27me3 (repressive) and H3K4me3 (activating) and are thus termed bivalent. It was previously observed that bivalent genes in human ES cells (hESC) are frequent targets for hypermethylation in human cancers, and depletion of DNA methylation in mouse embryonic stem cells has a marked impact on H3K27me3 distribution at bivalent promoters. However, only a fraction of bivalent genes in stem cells are targets of hypermethylation in cancer, and it is currently unclear whether all bivalent promoters are equally sensitive to DNA hypomethylation and whether H3K4me3 levels play a role in the interplay between DNA methylation and H3K27me3. RESULTS We report the sub-classification of bivalent promoters into two groups-promoters with a high H3K27me3:H3K4me3 (hiBiv) ratio or promoters with a low H3K27me3:H3K4me3 ratio (loBiv). HiBiv are enriched in canonical Polycomb components, show a higher degree of local intrachromosomal contacts and are highly sensitive to DNA hypomethylation in terms of H3K27me3 depletion from broad Polycomb domains. In contrast, loBiv promoters are enriched in non-canonical Polycomb components, show lower intrachromosomal contacts and are less sensitive to DNA hypomethylation at the same genomic resolution. Multiple systems reveal that hiBiv promoters are more depleted of Polycomb complexes than loBiv promoters following a reduction in DNA methylation, and we demonstrate that H3K27me3 re-accumulates at promoters when DNA methylation is restored. In human cancer, we show that hiBiv promoters lose H3K27me3 and are more susceptible to DNA hypermethylation than loBiv promoters. CONCLUSION We conclude that bivalency as a general term to describe mammalian promoters is an over-simplification and our sub-classification has revealed novel insights into the interplay between the largely antagonistic presence of DNA methylation and Polycomb systems at bivalent promoters. This approach redefines molecular pathologies underlying disease in which global DNA methylation is aberrant or where Polycomb mutations are present.
Collapse
Affiliation(s)
- Donnchadh S. Dunican
- MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU Scotland
| | - Heidi K. Mjoseng
- MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU Scotland
| | - Leanne Duthie
- MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU Scotland
| | - Ilya M. Flyamer
- MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU Scotland
| | - Wendy A. Bickmore
- MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU Scotland
| | - Richard R. Meehan
- MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU Scotland
| |
Collapse
|
80
|
|
81
|
Johansen S, Gjerstorff MF. Interaction between Polycomb and SSX Proteins in Pericentromeric Heterochromatin Function and Its Implication in Cancer. Cells 2020; 9:cells9010226. [PMID: 31963307 PMCID: PMC7016822 DOI: 10.3390/cells9010226] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/13/2020] [Accepted: 01/14/2020] [Indexed: 01/10/2023] Open
Abstract
The stability of pericentromeric heterochromatin is maintained by repressive epigenetic control mechanisms, and failure to maintain this stability may cause severe diseases such as immune deficiency and cancer. Thus, deeper insight into the epigenetic regulation and deregulation of pericentromeric heterochromatin is of high priority. We and others have recently demonstrated that pericentromeric heterochromatin domains are often epigenetically reprogrammed by Polycomb proteins in premalignant and malignant cells to form large subnuclear structures known as Polycomb bodies. This may affect the regulation and stability of pericentromeric heterochromatin domains and/or the distribution of Polycomb factors to support tumorigeneses. Importantly, Polycomb bodies in cancer cells may be targeted by the cancer/testis-related SSX proteins to cause derepression and genomic instability of pericentromeric heterochromatin. This review will discuss the interplay between SSX and Polycomb factors in the repression and stability of pericentromeric heterochromatin and its possible implications for tumor biology.
Collapse
Affiliation(s)
- Simone Johansen
- Department of Cancer and Inflammation Research, Institute for Molecular Medicine, University of Southern Denmark, 5000 Odense, Denmark;
| | - Morten Frier Gjerstorff
- Department of Cancer and Inflammation Research, Institute for Molecular Medicine, University of Southern Denmark, 5000 Odense, Denmark;
- Department of Oncology, Odense University Hospital, 5000 Odense, Denmark
- Academy of Geriatric Cancer Research (AgeCare), Odense University Hospital, 5000 Odense, Denmark
- Correspondence: ; Tel.: +45-21261563
| |
Collapse
|
82
|
Kim J, Kingston RE. The CBX family of proteins in transcriptional repression and memory. J Biosci 2020; 45:16. [PMID: 31965994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
For mammals to develop properly, master regulatory genes must be repressed appropriately in a heritable manner. This review concerns the Polycomb Repressive Complex 1 (PRC1) family and the relationship between the establishment of repression and memory of the repressed state. The primary focus is on the CBX family of proteins in PRC1 complexes and their role in both chromatin compaction and phase separation. These two activities are linked and might contribute to both repression and memory.
Collapse
Affiliation(s)
- Jongmin Kim
- Department of Molecular Biology and MGH Research Institute, Massachusetts General Hospital, Boston, MA, USA
| | | |
Collapse
|
83
|
Jansz N, Nesterova T, Keniry A, Iminitoff M, Hickey PF, Pintacuda G, Masui O, Kobelke S, Geoghegan N, Breslin KA, Willson TA, Rogers K, Kay GF, Fox AH, Koseki H, Brockdorff N, Murphy JM, Blewitt ME. Smchd1 Targeting to the Inactive X Is Dependent on the Xist-HnrnpK-PRC1 Pathway. Cell Rep 2019; 25:1912-1923.e9. [PMID: 30428357 DOI: 10.1016/j.celrep.2018.10.044] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 09/06/2018] [Accepted: 10/11/2018] [Indexed: 01/08/2023] Open
Abstract
We and others have recently reported that the SMC protein Smchd1 is a regulator of chromosome conformation. Smchd1 is critical for the structure of the inactive X chromosome and at autosomal targets such as the Hox genes. However, it is unknown how Smchd1 is recruited to these sites. Here, we report that Smchd1 localizes to the inactive X via the Xist-HnrnpK-PRC1 (polycomb repressive complex 1) pathway. Contrary to previous reports, Smchd1 does not bind Xist or other RNA molecules with any specificity. Rather, the localization of Smchd1 to the inactive X is H2AK119ub dependent. Following perturbation of this interaction, Smchd1 is destabilized, which has consequences for gene silencing genome-wide. Our work adds Smchd1 to the PRC1 silencing pathway for X chromosome inactivation.
Collapse
Affiliation(s)
- Natasha Jansz
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Tatyana Nesterova
- Developmental Epigenetics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Andrew Keniry
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Megan Iminitoff
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia
| | - Peter F Hickey
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Greta Pintacuda
- Developmental Epigenetics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Osamu Masui
- Centre for Integrative Medical Sciences, RIKEN Yokohama Institute, 1-7-22, Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Simon Kobelke
- School of Human Sciences, The University of Western Australia, Crawley, WA 6009, Australia
| | - Niall Geoghegan
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Kelsey A Breslin
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia
| | - Tracy A Willson
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia
| | - Kelly Rogers
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Graham F Kay
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Archa H Fox
- School of Human Sciences, The University of Western Australia, Crawley, WA 6009, Australia
| | - Haruhiko Koseki
- Centre for Integrative Medical Sciences, RIKEN Yokohama Institute, 1-7-22, Suehiro-cho, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Neil Brockdorff
- Developmental Epigenetics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - James M Murphy
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Marnie E Blewitt
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3010, Australia; Department of Genetics, University of Melbourne, Melbourne, VIC 3010, Australia.
| |
Collapse
|
84
|
Cheutin T, Cavalli G. The multiscale effects of polycomb mechanisms on 3D chromatin folding. Crit Rev Biochem Mol Biol 2019; 54:399-417. [PMID: 31698957 DOI: 10.1080/10409238.2019.1679082] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 10/08/2019] [Accepted: 10/08/2019] [Indexed: 12/30/2022]
Abstract
Polycomb group (PcG) proteins silence master regulatory genes required to properly confer cell identity during the development of both Drosophila and mammals. They may act through chromatin compaction and higher-order folding of chromatin inside the cell nucleus. During the last decade, analysis on interphase chromosome architecture discovered self-interacting regions named topologically associated domains (TADs). TADs result from the 3D chromatin folding of a succession of transcribed and repressed epigenomic domains and from loop extrusion mediated by cohesin/CTCF in mammals. Polycomb silenced chromatin constitutes one type of repressed epigenomic domains which form compacted nano-compartments inside cell nuclei. Recruitment of canonical PcG proteins on chromatin relies on initial binding to discrete elements and further spreading into large chromatin domains covered with H3K27me3. Some of these discrete elements have a bivalent nature both in mammals and Drosophila and are dynamically regulated during development. Loops can occur between them, suggesting that their interaction plays both functional and structural roles. Formation of large chromatin domains covered by H3K27me3 seems crucial for PcG silencing and PcG proteins might exert their function through compaction of these domains in both mammals and flies, rather than by directly controlling the nucleosomal accessibility of discrete regulatory elements. In addition, PcG chromatin domains interact over long genomic distances, shaping a higher-order chromatin network. Therefore, PcG silencing might rely on multiscale chromatin folding to maintain cell identity during differentiation.
Collapse
Affiliation(s)
- Thierry Cheutin
- Institute of Human Genetics, CNRS and the University of Montpellier, Montpellier, France
| | - Giacomo Cavalli
- Institute of Human Genetics, CNRS and the University of Montpellier, Montpellier, France
| |
Collapse
|
85
|
Lamb KN, Bsteh D, Dishman SN, Moussa HF, Fan H, Stuckey JI, Norris JL, Cholensky SH, Li D, Wang J, Sagum C, Stanton BZ, Bedford MT, Pearce KH, Kenakin TP, Kireev DB, Wang GG, James LI, Bell O, Frye SV. Discovery and Characterization of a Cellular Potent Positive Allosteric Modulator of the Polycomb Repressive Complex 1 Chromodomain, CBX7. Cell Chem Biol 2019; 26:1365-1379.e22. [PMID: 31422906 DOI: 10.1016/j.chembiol.2019.07.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Revised: 06/08/2019] [Accepted: 07/25/2019] [Indexed: 12/13/2022]
Abstract
Polycomb-directed repression of gene expression is frequently misregulated in human diseases. A quantitative and target-specific cellular assay was utilized to discover the first potent positive allosteric modulator (PAM) peptidomimetic, UNC4976, of nucleic acid binding by CBX7, a chromodomain methyl-lysine reader of Polycomb repressive complex 1. The PAM activity of UNC4976 resulted in enhanced efficacy across three orthogonal cellular assays by simultaneously antagonizing H3K27me3-specific recruitment of CBX7 to target genes while increasing non-specific binding to DNA and RNA. PAM activity thereby reequilibrates PRC1 away from H3K27me3 target regions. Together, our discovery and characterization of UNC4976 not only revealed the most cellularly potent PRC1-specific chemical probe to date, but also uncovers a potential mechanism of Polycomb regulation with implications for non-histone lysine methylated interaction partners.
Collapse
Affiliation(s)
- Kelsey N Lamb
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Daniel Bsteh
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria; Department of Biochemistry and Molecular Medicine and Norris Comprehensive Cancer Center, Keck School of Medicine of the University of Southern California, Los Angeles, CA 90033, USA
| | - Sarah N Dishman
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Hagar F Moussa
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Huitao Fan
- Lineberger Comprehensive Cancer Center, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jacob I Stuckey
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jacqueline L Norris
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Stephanie H Cholensky
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dongxu Li
- Lineberger Comprehensive Cancer Center, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jingkui Wang
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Cari Sagum
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Benjamin Z Stanton
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences NIH, Rockville, MD 20850, USA
| | - Mark T Bedford
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Kenneth H Pearce
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Terry P Kenakin
- Department of Pharmacology, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dmitri B Kireev
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Gang Greg Wang
- Lineberger Comprehensive Cancer Center, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Lindsey I James
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Oliver Bell
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria; Department of Biochemistry and Molecular Medicine and Norris Comprehensive Cancer Center, Keck School of Medicine of the University of Southern California, Los Angeles, CA 90033, USA.
| | - Stephen V Frye
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| |
Collapse
|
86
|
Tsuboi M, Hirabayashi Y, Gotoh Y. Diverse gene regulatory mechanisms mediated by Polycomb group proteins during neural development. Curr Opin Neurobiol 2019; 59:164-173. [PMID: 31398486 DOI: 10.1016/j.conb.2019.07.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 07/07/2019] [Indexed: 12/26/2022]
Abstract
While all the developmental genes are temporarily repressed for future activation in the pluripotent stem cells, non-neural genes become persistently repressed in the course of commitment to the neuronal lineage. Although Polycomb group proteins (PcG) are key factors for both temporary and persistent repression of the developmental genes, how the same group of proteins can differentially repress target genes remains unclarified. The identification of a variety of PcG complexes and activities sheds light on these issues. In this review, based on the recent findings including those with the use of interactome and Chromosome Conformation Capture (3C)-type analyses, we summarize the molecular mechanisms of PcG-mediated gene regulation and discuss how PcG regulates cell fate specification during neural development.
Collapse
Affiliation(s)
- Masafumi Tsuboi
- Graduate School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan.
| | - Yusuke Hirabayashi
- Graduate School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yukiko Gotoh
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan; International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo 113-0033, Japan
| |
Collapse
|
87
|
Abstract
As the process that silences gene expression ensues during development, the stage is set for the activity of Polycomb-repressive complex 2 (PRC2) to maintain these repressed gene profiles. PRC2 catalyzes a specific histone posttranslational modification (hPTM) that fosters chromatin compaction. PRC2 also facilitates the inheritance of this hPTM through its self-contained "write and read" activities, key to preserving cellular identity during cell division. As these changes in gene expression occur without changes in DNA sequence and are inherited, the process is epigenetic in scope. Mutants of mammalian PRC2 or of its histone substrate contribute to the cancer process and other diseases, and research into these aberrant pathways is yielding viable candidates for therapeutic targeting. The effectiveness of PRC2 hinges on its being recruited to the proper chromatin sites; however, resolving the determinants to this process in the mammalian case was not straightforward and thus piqued the interest of many in the field. Here, we chronicle the latest advances toward exposing mammalian PRC2 and its high maintenance.
Collapse
Affiliation(s)
- Jia-Ray Yu
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Chul-Hwan Lee
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Ozgur Oksuz
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - James M Stafford
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Danny Reinberg
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| |
Collapse
|
88
|
Vidal M. Polycomb Assemblies Multitask to Regulate Transcription. EPIGENOMES 2019; 3:12. [PMID: 34968234 PMCID: PMC8594731 DOI: 10.3390/epigenomes3020012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 06/14/2019] [Accepted: 06/16/2019] [Indexed: 02/06/2023] Open
Abstract
The Polycomb system is made of an evolutionary ancient group of proteins, present throughout plants and animals. Known initially from developmental studies with the fly Drosophila melanogaster, they were associated with stable sustainment of gene repression and maintenance of cell identity. Acting as multiprotein assemblies with an ability to modify chromatin, through chemical additions to histones and organization of topological domains, they have been involved subsequently in control of developmental transitions and in cell homeostasis. Recent work has unveiled an association of Polycomb components with transcriptionally active loci and the promotion of gene expression, in clear contrast with conventional recognition as repressors. Focusing on mammalian models, I review here advances concerning roles in transcriptional control. Among new findings highlighted is the regulation of their catalytic properties, recruiting to targets, and activities in chromatin organization and compartmentalization. The need for a more integrated approach to the study of the Polycomb system, given its fundamental complexity and its adaptation to cell context, is discussed.
Collapse
Affiliation(s)
- Miguel Vidal
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas, Ramiro de Maeztu 9, 28040 Madrid, Spain
| |
Collapse
|
89
|
Plys AJ, Davis CP, Kim J, Rizki G, Keenen MM, Marr SK, Kingston RE. Phase separation of Polycomb-repressive complex 1 is governed by a charged disordered region of CBX2. Genes Dev 2019; 33:799-813. [PMID: 31171700 PMCID: PMC6601514 DOI: 10.1101/gad.326488.119] [Citation(s) in RCA: 224] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 05/08/2019] [Indexed: 12/15/2022]
Abstract
Here, Plys et al. demonstrate that reconstituted PRC1 readily phase-separates into droplets in vitro at low concentrations and physiological salt conditions, and this behavior is driven by the CBX2 subunit. Mammalian development requires effective mechanisms to repress genes whose expression would generate inappropriately specified cells. The Polycomb-repressive complex 1 (PRC1) family complexes are central to maintaining this repression. These include a set of canonical PRC1 complexes, each of which contains four core proteins, including one from the CBX family. These complexes have been shown previously to reside in membraneless organelles called Polycomb bodies, leading to speculation that canonical PRC1 might be found in a separate phase from the rest of the nucleus. We show here that reconstituted PRC1 readily phase-separates into droplets in vitro at low concentrations and physiological salt conditions. This behavior is driven by the CBX2 subunit. Point mutations in an internal domain of Cbx2 eliminate phase separation. These same point mutations eliminate the formation of puncta in cells and have been shown previously to eliminate nucleosome compaction in vitro and generate axial patterning defects in mice. Thus, the domain of CBX2 that is important for phase separation is the same domain shown previously to be important for chromatin compaction and proper development, raising the possibility of a mechanistic or evolutionary link between these activities.
Collapse
Affiliation(s)
- Aaron J Plys
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Christopher P Davis
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Jongmin Kim
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Gizem Rizki
- Department of Stem Cell and Regenerative Biology, Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Madeline M Keenen
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Sharon K Marr
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Robert E Kingston
- Department of Molecular Biology, Massachusetts General Hospital Research Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| |
Collapse
|
90
|
Fursova NA, Blackledge NP, Nakayama M, Ito S, Koseki Y, Farcas AM, King HW, Koseki H, Klose RJ. Synergy between Variant PRC1 Complexes Defines Polycomb-Mediated Gene Repression. Mol Cell 2019; 74:1020-1036.e8. [PMID: 31029541 PMCID: PMC6561741 DOI: 10.1016/j.molcel.2019.03.024] [Citation(s) in RCA: 159] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 02/04/2019] [Accepted: 03/21/2019] [Indexed: 01/30/2023]
Abstract
The Polycomb system modifies chromatin and plays an essential role in repressing gene expression to control normal mammalian development. However, the components and mechanisms that define how Polycomb protein complexes achieve this remain enigmatic. Here, we use combinatorial genetic perturbation coupled with quantitative genomics to discover the central determinants of Polycomb-mediated gene repression in mouse embryonic stem cells. We demonstrate that canonical Polycomb repressive complex 1 (PRC1), which mediates higher-order chromatin structures, contributes little to gene repression. Instead, we uncover an unexpectedly high degree of synergy between variant PRC1 complexes, which is fundamental to gene repression. We further demonstrate that variant PRC1 complexes are responsible for distinct pools of H2A monoubiquitylation that are associated with repression of Polycomb target genes and silencing during X chromosome inactivation. Together, these discoveries reveal a new variant PRC1-dependent logic for Polycomb-mediated gene repression.
Collapse
Affiliation(s)
- Nadezda A Fursova
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Neil P Blackledge
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Manabu Nakayama
- Laboratory of Medical Omics Research, Department of Frontier Research and Development, Kazusa DNA Research Institute, 2-6-7 Kazusa-Kamatari, Kisarazu, Chiba 292-0818, Japan
| | - Shinsuke Ito
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Yoko Koseki
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Anca M Farcas
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Hamish W King
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Haruhiko Koseki
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan; AMED-CREST, Japanese Agency for Medical Research and Development, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Robert J Klose
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
| |
Collapse
|
91
|
Bracken AP, Brien GL, Verrijzer CP. Dangerous liaisons: interplay between SWI/SNF, NuRD, and Polycomb in chromatin regulation and cancer. Genes Dev 2019; 33:936-959. [PMID: 31123059 PMCID: PMC6672049 DOI: 10.1101/gad.326066.119] [Citation(s) in RCA: 105] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In this review, Bracken et al. discuss the functional organization and biochemical activities of remodelers and Polycomb and explore how they work together to control cell differentiation and the maintenance of cell identity. They also discuss how mutations in the genes encoding these various chromatin regulators contribute to oncogenesis by disrupting the chromatin equilibrium. Changes in chromatin structure mediated by ATP-dependent nucleosome remodelers and histone modifying enzymes are integral to the process of gene regulation. Here, we review the roles of the SWI/SNF (switch/sucrose nonfermenting) and NuRD (nucleosome remodeling and deacetylase) and the Polycomb system in chromatin regulation and cancer. First, we discuss the basic molecular mechanism of nucleosome remodeling, and how this controls gene transcription. Next, we provide an overview of the functional organization and biochemical activities of SWI/SNF, NuRD, and Polycomb complexes. We describe how, in metazoans, the balance of these activities is central to the proper regulation of gene expression and cellular identity during development. Whereas SWI/SNF counteracts Polycomb, NuRD facilitates Polycomb repression on chromatin. Finally, we discuss how disruptions of this regulatory equilibrium contribute to oncogenesis, and how new insights into the biological functions of remodelers and Polycombs are opening avenues for therapeutic interventions on a broad range of cancer types.
Collapse
Affiliation(s)
- Adrian P Bracken
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
| | - Gerard L Brien
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
| | - C Peter Verrijzer
- Department of Biochemistry, Erasmus University Medical Center, 3000 DR Rotterdam, the Netherlands
| |
Collapse
|
92
|
Garcia-Moreno SA, Lin YT, Futtner CR, Salamone IM, Capel B, Maatouk DM. CBX2 is required to stabilize the testis pathway by repressing Wnt signaling. PLoS Genet 2019; 15:e1007895. [PMID: 31116734 PMCID: PMC6548405 DOI: 10.1371/journal.pgen.1007895] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 06/04/2019] [Accepted: 04/12/2019] [Indexed: 12/25/2022] Open
Abstract
XX and XY fetal gonads are initially bipotential, poised between the ovary and testis fate. Multiple lines of evidence suggest that commitment to testis fate requires the repression of genes associated with ovary fate. It was previously shown that loss of CBX2, the subunit of the Polycomb Repressive Complex 1 (PRC1) that binds H3K27me3 and mediates silencing, leads to ovary development in XY mice and humans. While it had been proposed that CBX2 is an activator of the testis-determining gene Sry, we investigated the alternative possibility that CBX2 has a direct role as a repressor of the antagonistic ovary-promoting pathway. To investigate this possibility, we developed a quantitative genome-wide profile of the repressive histone mark H3K27me3 and its active counterpart H3K4me3 in isolated XY and XX gonadal supporting cells before and after sex determination. We show that testis and ovary sex-determining (SD) genes are bivalent before sex determination, providing insight into how the bipotential state of the gonad is established at the epigenetic level. After sex determination, many SD genes of the alternate pathway remain bivalent, possibly contributing to the ability of these cells to transdifferentiate even in adults. The finding that many genes in the Wnt signaling pathway were targeted for H3K27me3-mediated repression in Sertoli cells led us to test whether deletion of Wnt4 could rescue testis development in Cbx2 mutants. We show that Sry expression and testis development were rescued in XY Cbx2-/-;Wnt4-/- mice. Furthermore, we show that CBX2 directly binds the downstream Wnt signaler Lef1, an ovary-promoting gene that remains bivalent in Sertoli cells. Our results suggest that stabilization of the testis fate requires CBX2-mediated repression of bivalent ovary-determining genes, which would otherwise block testis development. During development, the bipotential fetal gonad can commit to the testis fate or to the ovary fate. Mutation of the epigenetic regulator CBX2 leads to ovary development in XY embryos, suggesting a critical role for chromatin remodeling during sex determination. However, the epigenetic mechanisms that regulate the testis vs. ovary cell-fate decision in the mammalian bipotential gonad are poorly understood. In this study, we developed a genome-wide profile of two histone modifications that play critical roles during development: H3K27me3 (repressive) and H3K4me3 (active). We find that sex-determining genes that are initially co-expressed in XX and XY bipotential gonads are bivalent (marked by both H3K4me3 and H3K27me3) prior to sex determination, poised to engage either the testis or ovary fate. Remarkably, after sex determination, repressed genes that promote the alternate fate remain bivalent. We show that stabilization of the testis fate requires CBX2-mediated repression of bivalent ovary-determining genes, which would otherwise block testis development. Our study provides insight into how the bipotential state of the gonad is established at the epigenetic level, and how the testis fate is stabilized by repression of the ovary fate during sex determination.
Collapse
Affiliation(s)
- S. Alexandra Garcia-Moreno
- Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois, United States of America
| | - Yi-Tzu Lin
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Christopher R. Futtner
- Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois, United States of America
| | - Isabella M. Salamone
- Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois, United States of America
| | - Blanche Capel
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
| | - Danielle M. Maatouk
- Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois, United States of America
| |
Collapse
|
93
|
Colombo M, Pessey O, Marcia M. Topology and enzymatic properties of a canonical Polycomb repressive complex 1 isoform. FEBS Lett 2019; 593:1837-1848. [PMID: 31093962 PMCID: PMC6771824 DOI: 10.1002/1873-3468.13442] [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: 01/25/2019] [Revised: 05/10/2019] [Accepted: 05/13/2019] [Indexed: 11/28/2022]
Abstract
Polycomb repressive complex 1 (PRC1) catalyses monoubiquitination of histone H2A on Lys119, promoting gene silencing. Cells at different developmental stages and in different tissues express different PRC1 isoforms. The topology, subunit composition, structural architecture and molecular mechanism of most of these isoforms are still poorly characterized. Here, we have purified a PRC1 isoform comprising subunits RING1B, PCGF2, CBX2 and PHC2, two stable subcomplexes (RING1B‐PCGF2 and RING1B‐PHC2) and the catalytic subunit RING1B in isolation. By crosslinking mass spectrometry, we identified novel interactions between RING1B and the three non‐catalytic subunits. Biochemical, biophysical, and enzymatic data suggest that CBX2 and PHC2 play a structural role, whereas PCGF2 also modulates catalysis. Our data offer insights into the molecular architecture of PRC1 and its histone ubiquitination activity.
Collapse
Affiliation(s)
- Matteo Colombo
- European Molecular Biology Laboratory, Grenoble Outstation, Grenoble, France
| | - Ombeline Pessey
- European Molecular Biology Laboratory, Grenoble Outstation, Grenoble, France
| | - Marco Marcia
- European Molecular Biology Laboratory, Grenoble Outstation, Grenoble, France
| |
Collapse
|
94
|
Brand M, Nakka K, Zhu J, Dilworth FJ. Polycomb/Trithorax Antagonism: Cellular Memory in Stem Cell Fate and Function. Cell Stem Cell 2019; 24:518-533. [PMID: 30951661 PMCID: PMC6866673 DOI: 10.1016/j.stem.2019.03.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Stem cells are continuously challenged with the decision to either self-renew or adopt a new fate. Self-renewal is regulated by a system of cellular memory, which must be bypassed for differentiation. Previous studies have identified Polycomb group (PcG) and Trithorax group (TrxG) proteins as key modulators of cellular memory. In this Perspective, we draw from embryonic and adult stem cell studies to discuss the complex roles played by PcG and TrxG in maintaining cell identity while allowing for microenvironment-mediated alterations in cell fate. Finally, we discuss the potential for targeting these proteins as a therapeutic approach in cancer.
Collapse
Affiliation(s)
- Marjorie Brand
- Sprott Center for Stem Cell Research, Ottawa Hospital Research Institute, Ottawa, ON, Canada K1H 8L6; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8L6.
| | - Kiran Nakka
- Sprott Center for Stem Cell Research, Ottawa Hospital Research Institute, Ottawa, ON, Canada K1H 8L6; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8L6
| | - Jiayu Zhu
- Sprott Center for Stem Cell Research, Ottawa Hospital Research Institute, Ottawa, ON, Canada K1H 8L6; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8L6
| | - F Jeffrey Dilworth
- Sprott Center for Stem Cell Research, Ottawa Hospital Research Institute, Ottawa, ON, Canada K1H 8L6; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8L6.
| |
Collapse
|
95
|
Illingworth RS. Chromatin folding and nuclear architecture: PRC1 function in 3D. Curr Opin Genet Dev 2019; 55:82-90. [PMID: 31323466 PMCID: PMC6859790 DOI: 10.1016/j.gde.2019.06.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 12/20/2022]
Abstract
Embryonic development requires the intricate balance between the expansion and specialisation of defined cell types in time and space. The gene expression programmes that underpin this balance are regulated, in part, by modulating the chemical and structural state of chromatin. Polycomb repressive complexes (PRCs), a family of essential developmental regulators, operate at this level to stabilise or perpetuate a repressed but transcriptionally poised chromatin configuration. This dynamic state is required to control the timely initiation of productive gene transcription during embryonic development. The two major PRCs cooperate to target the genome, but it is PRC1 that appears to be the primary effector that controls gene expression. In this review I will discuss recent findings relating to how PRC1 alters chromatin accessibility, folding and global 3D nuclear organisation to control gene transcription.
Collapse
Affiliation(s)
- Robert S Illingworth
- MRC Centre for Regenerative Medicine, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh BioQuarter, 5 Little France Drive, Edinburgh, EH16 4UU, United Kingdom.
| |
Collapse
|
96
|
Stévant I, Nef S. Genetic Control of Gonadal Sex Determination and Development. Trends Genet 2019; 35:346-358. [PMID: 30902461 DOI: 10.1016/j.tig.2019.02.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 02/15/2019] [Accepted: 02/23/2019] [Indexed: 10/27/2022]
Abstract
Sex determination is the process by which the bipotential gonads develop as either testes or ovaries. With two distinct potential outcomes, the gonadal primordium offers a unique model for the study of cell fate specification and how distinct cell populations diverge from multipotent progenitors. This review focuses on recent advances in our understanding of the genetic programs and epigenetic mechanisms that regulate gonadal sex determination and the regulation of cell fate commitment in the bipotential gonads. We rely primarily on mouse data to illuminate the complex and dynamic genetic programs controlling cell fate decision and sex-specific cell differentiation during gonadal formation and gonadal sex determination.
Collapse
Affiliation(s)
- Isabelle Stévant
- Department of Genetic Medicine and Development, University of Geneva, 1211 Geneva, Switzerland; iGE3, Institute of Genetics and Genomics of Geneva, University of Geneva, 1211 Geneva, Switzerland; SIB, Swiss Institute of Bioinformatics, University of Geneva, 1211 Geneva, Switzerland
| | - Serge Nef
- Department of Genetic Medicine and Development, University of Geneva, 1211 Geneva, Switzerland; iGE3, Institute of Genetics and Genomics of Geneva, University of Geneva, 1211 Geneva, Switzerland.
| |
Collapse
|
97
|
Affiliation(s)
- Sandip De
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Judith A Kassis
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
98
|
Loubiere V, Martinez AM, Cavalli G. Cell Fate and Developmental Regulation Dynamics by Polycomb Proteins and 3D Genome Architecture. Bioessays 2019; 41:e1800222. [PMID: 30793782 DOI: 10.1002/bies.201800222] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/22/2018] [Indexed: 12/14/2022]
Abstract
Targeted transitions in chromatin states at thousands of genes are essential drivers of eukaryotic development. Therefore, understanding the in vivo dynamics of epigenetic regulators is crucial for deciphering the mechanisms underpinning cell fate decisions. This review illustrates how, in addition to its cell memory function, the Polycomb group of transcriptional regulators orchestrates temporal, cell and tissue-specific expression of master genes during development. These highly sophisticated developmental transitions are dependent on the context- and tissue-specific assembly of the different types of Polycomb Group (PcG) complexes, which regulates their targeting and/or activities on chromatin. Here, an overview is provided of how PcG complexes function at multiple scales to regulate transcription, local chromatin environment, and higher order structures that support normal differentiation and are perturbed in tumorigenesis.
Collapse
Affiliation(s)
- Vincent Loubiere
- Institute of Human Genetics, UMR 9002, CNRS and University of Montpellier, 34396, Montpellier, France
| | - Anne-Marie Martinez
- Institute of Human Genetics, UMR 9002, CNRS and University of Montpellier, 34396, Montpellier, France
| | - Giacomo Cavalli
- Institute of Human Genetics, UMR 9002, CNRS and University of Montpellier, 34396, Montpellier, France
| |
Collapse
|
99
|
Tatavosian R, Kent S, Brown K, Yao T, Duc HN, Huynh TN, Zhen CY, Ma B, Wang H, Ren X. Nuclear condensates of the Polycomb protein chromobox 2 (CBX2) assemble through phase separation. J Biol Chem 2018; 294:1451-1463. [PMID: 30514760 DOI: 10.1074/jbc.ra118.006620] [Citation(s) in RCA: 228] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 11/28/2018] [Indexed: 01/01/2023] Open
Abstract
Polycomb group (PcG) proteins repress master regulators of development and differentiation through organization of chromatin structure. Mutation and dysregulation of PcG genes cause developmental defects and cancer. PcG proteins form condensates in the cell nucleus, and these condensates are the physical sites of PcG-targeted gene silencing via formation of facultative heterochromatin. However, the physiochemical principles underlying the formation of PcG condensates remain unknown, and their determination could shed light on how these condensates compact chromatin. Using fluorescence live-cell imaging, we observed that the Polycomb repressive complex 1 (PRC1) protein chromobox 2 (CBX2), a member of the CBX protein family, undergoes phase separation to form condensates and that the CBX2 condensates exhibit liquid-like properties. Using site-directed mutagenesis, we demonstrated that the conserved residues of CBX2 within the intrinsically disordered region (IDR), which is the region for compaction of chromatin in vitro, promote the condensate formation both in vitro and in vivo We showed that the CBX2 condensates concentrate DNA and nucleosomes. Using genetic engineering, we report that trimethylation of Lys-27 at histone H3 (H3K27me3), a marker of heterochromatin formation produced by PRC2, had minimal effects on the CBX2 condensate formation. We further demonstrated that the CBX2 condensate formation does not require CBX2-PRC1 subunits; however, the condensate formation of CBX2-PRC1 subunits depends on CBX2, suggesting a mechanism underlying the assembly of CBX2-PRC1 condensates. In summary, our results reveal that PcG condensates assemble through liquid-liquid phase separation (LLPS) and suggest that phase-separated condensates can organize PcG-bound chromatin.
Collapse
Affiliation(s)
- Roubina Tatavosian
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Samantha Kent
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Kyle Brown
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Tingting Yao
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Huy Nguyen Duc
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Thao Ngoc Huynh
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Chao Yu Zhen
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Brian Ma
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Haobin Wang
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364
| | - Xiaojun Ren
- Department of Chemistry, University of Colorado, Denver, Colorado 80217-3364.
| |
Collapse
|
100
|
Cheutin T, Cavalli G. Loss of PRC1 induces higher-order opening of Hox loci independently of transcription during Drosophila embryogenesis. Nat Commun 2018; 9:3898. [PMID: 30254245 PMCID: PMC6156336 DOI: 10.1038/s41467-018-05945-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 07/30/2018] [Indexed: 12/14/2022] Open
Abstract
Polycomb-group proteins are conserved chromatin factors that maintain the silencing of key developmental genes, notably the Hox gene clusters, outside of their expression domains. Depletion of Polycomb repressive complex 1 (PRC1) proteins typically results in chromatin unfolding, as well as ectopic transcription. To disentangle these two phenomena, here we analyze the temporal function of two PRC1 proteins, Polyhomeotic (Ph) and Polycomb (Pc), on Hox gene clusters during Drosophila embryogenesis. We show that the absence of Ph or Pc affects the higher-order chromatin folding of Hox clusters prior to ectopic Hox gene transcription, demonstrating that PRC1 primary function during early embryogenesis is to compact its target chromatin. Moreover, the differential effects of Ph and Pc on Hox cluster folding match the differences in ectopic Hox gene expression observed in these two mutants. Our data suggest that PRC1 maintains gene silencing by folding chromatin domains and impose architectural layer to gene regulation. Loss of Polycomb repressive complex 1 (PRC1) proteins usually results in both chromatin unfolding and ectopic transcription. Here, the authors analyze the temporal function of two PRC1 proteins during Drosophila embryogenesis and provide evidence that PRC1 maintains gene silencing by folding chromatin domains.
Collapse
Affiliation(s)
- Thierry Cheutin
- Institute of Human Genetics, CNRS and the University of Montpellier, Montpellier, France.
| | - Giacomo Cavalli
- Institute of Human Genetics, CNRS and the University of Montpellier, Montpellier, France.
| |
Collapse
|