1
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Tamburri S, Rustichelli S, Amato S, Pasini D. Navigating the complexity of Polycomb repression: Enzymatic cores and regulatory modules. Mol Cell 2024:S1097-2765(24)00628-2. [PMID: 39178860 DOI: 10.1016/j.molcel.2024.07.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2024] [Revised: 07/12/2024] [Accepted: 07/30/2024] [Indexed: 08/26/2024]
Abstract
Polycomb proteins are a fundamental repressive system that plays crucial developmental roles by orchestrating cell-type-specific transcription programs that govern cell identity. Direct alterations of Polycomb activity are indeed implicated in human pathologies, including developmental disorders and cancer. General Polycomb repression is coordinated by three distinct activities that regulate the deposition of two histone post-translational modifications: tri-methylation of histone H3 lysine 27 (H3K27me3) and histone H2A at lysine 119 (H2AK119ub1). These activities exist in large and heterogeneous multiprotein ensembles consisting of common enzymatic cores regulated by heterogeneous non-catalytic modules composed of a large number of accessory proteins with diverse biochemical properties. Here, we have analyzed the current molecular knowledge, focusing on the functional interaction between the core enzymatic activities and their regulation mediated by distinct accessory modules. This provides a comprehensive analysis of the molecular details that control the establishment and maintenance of Polycomb repression, examining their underlying coordination and highlighting missing information and emerging new features of Polycomb-mediated transcriptional control.
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Affiliation(s)
- Simone Tamburri
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy; University of Milan, Department of Health Sciences, Via A. di Rudinì 8, 20142 Milan, Italy.
| | - Samantha Rustichelli
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Simona Amato
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Diego Pasini
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy; University of Milan, Department of Health Sciences, Via A. di Rudinì 8, 20142 Milan, Italy.
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2
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Shi TH, Sugishita H, Gotoh Y. Crosstalk within and beyond the Polycomb repressive system. J Cell Biol 2024; 223:e202311021. [PMID: 38506728 PMCID: PMC10955045 DOI: 10.1083/jcb.202311021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 03/01/2024] [Accepted: 03/04/2024] [Indexed: 03/21/2024] Open
Abstract
The development of multicellular organisms depends on spatiotemporally controlled differentiation of numerous cell types and their maintenance. To generate such diversity based on the invariant genetic information stored in DNA, epigenetic mechanisms, which are heritable changes in gene function that do not involve alterations to the underlying DNA sequence, are required to establish and maintain unique gene expression programs. Polycomb repressive complexes represent a paradigm of epigenetic regulation of developmentally regulated genes, and the roles of these complexes as well as the epigenetic marks they deposit, namely H3K27me3 and H2AK119ub, have been extensively studied. However, an emerging theme from recent studies is that not only the autonomous functions of the Polycomb repressive system, but also crosstalks of Polycomb with other epigenetic modifications, are important for gene regulation. In this review, we summarize how these crosstalk mechanisms have improved our understanding of Polycomb biology and how such knowledge could help with the design of cancer treatments that target the dysregulated epigenome.
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Affiliation(s)
- Tianyi Hideyuki Shi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Hiroki Sugishita
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- International Research Center for Neurointelligence, The University of Tokyo, Tokyo, Japan
| | - Yukiko Gotoh
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- International Research Center for Neurointelligence, The University of Tokyo, Tokyo, Japan
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3
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Veronezi GMB, Ramachandran S. Nucleation and spreading maintain Polycomb domains every cell cycle. Cell Rep 2024; 43:114090. [PMID: 38607915 PMCID: PMC11179494 DOI: 10.1016/j.celrep.2024.114090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 02/07/2024] [Accepted: 03/26/2024] [Indexed: 04/14/2024] Open
Abstract
Gene repression by the Polycomb pathway is essential for metazoan development. Polycomb domains, characterized by trimethylation of histone H3 lysine 27 (H3K27me3), carry the memory of repression and hence need to be maintained to counter the dilution of parental H3K27me3 with unmodified H3 during replication. Yet, how locus-specific H3K27me3 is maintained through replication is unclear. To understand H3K27me3 recovery post-replication, we first define nucleation sites within each Polycomb domain in mouse embryonic stem cells. To map dynamics of H3K27me3 domains across the cell cycle, we develop CUT&Flow (coupling cleavage under target and tagmentation with flow cytometry). We show that post-replication recovery of Polycomb domains occurs by nucleation and spreading, using the same nucleation sites used during de novo domain formation. By using Polycomb repressive complex 2 (PRC2) subunit-specific inhibitors, we find that PRC2 targets nucleation sites post-replication independent of pre-existing H3K27me3. Thus, competition between H3K27me3 deposition and nucleosome turnover drives both de novo domain formation and maintenance during every cell cycle.
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Affiliation(s)
- Giovana M B Veronezi
- Molecular Biology Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Srinivas Ramachandran
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; RNA Bioscience Initiative, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
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4
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Camellato BR, Brosh R, Ashe HJ, Maurano MT, Boeke JD. Synthetic reversed sequences reveal default genomic states. Nature 2024; 628:373-380. [PMID: 38448583 PMCID: PMC11006607 DOI: 10.1038/s41586-024-07128-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 01/29/2024] [Indexed: 03/08/2024]
Abstract
Pervasive transcriptional activity is observed across diverse species. The genomes of extant organisms have undergone billions of years of evolution, making it unclear whether these genomic activities represent effects of selection or 'noise'1-4. Characterizing default genome states could help understand whether pervasive transcriptional activity has biological meaning. Here we addressed this question by introducing a synthetic 101-kb locus into the genomes of Saccharomyces cerevisiae and Mus musculus and characterizing genomic activity. The locus was designed by reversing but not complementing human HPRT1, including its flanking regions, thus retaining basic features of the natural sequence but ablating evolved coding or regulatory information. We observed widespread activity of both reversed and native HPRT1 loci in yeast, despite the lack of evolved yeast promoters. By contrast, the reversed locus displayed no activity at all in mouse embryonic stem cells, and instead exhibited repressive chromatin signatures. The repressive signature was alleviated in a locus variant lacking CpG dinucleotides; nevertheless, this variant was also transcriptionally inactive. These results show that synthetic genomic sequences that lack coding information are active in yeast, but inactive in mouse embryonic stem cells, consistent with a major difference in 'default genomic states' between these two divergent eukaryotic cell types, with implications for understanding pervasive transcription, horizontal transfer of genetic information and the birth of new genes.
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Affiliation(s)
| | - Ran Brosh
- Institute for Systems Genetics, NYU Langone Health, New York, NY, USA
| | - Hannah J Ashe
- Institute for Systems Genetics, NYU Langone Health, New York, NY, USA
| | - Matthew T Maurano
- Institute for Systems Genetics, NYU Langone Health, New York, NY, USA
- Department of Pathology, NYU Langone Health, New York, NY, USA
| | - Jef D Boeke
- Institute for Systems Genetics, NYU Langone Health, New York, NY, USA.
- Department of Biochemistry and Molecular Pharmacology, NYU Langone Health, New York, NY, USA.
- Department of Biomedical Engineering, NYU Tandon School of Engineering, New York, NY, USA.
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5
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Glancy E, Choy N, Eckersley-Maslin MA. Bivalent chromatin: a developmental balancing act tipped in cancer. Biochem Soc Trans 2024; 52:217-229. [PMID: 38385532 PMCID: PMC10903468 DOI: 10.1042/bst20230426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/23/2024]
Abstract
Bivalent chromatin is defined by the co-occurrence of otherwise opposing H3K4me3 and H3K27me3 modifications and is typically located at unmethylated promoters of lowly transcribed genes. In embryonic stem cells, bivalent chromatin has been proposed to poise developmental genes for future activation, silencing or stable repression upon lineage commitment. Normally, bivalent chromatin is kept in tight balance in cells, in part through the activity of the MLL/COMPASS-like and Polycomb repressive complexes that deposit the H3K4me3 and H3K27me3 modifications, respectively, but also emerging novel regulators including DPPA2/4, QSER1, BEND3, TET1 and METTL14. In cancers, both the deregulation of existing domains and the creation of de novo bivalent states is associated with either the activation or silencing of transcriptional programmes. This may facilitate diverse aspects of cancer pathology including epithelial-to-mesenchymal plasticity, chemoresistance and immune evasion. Here, we review current methods for detecting bivalent chromatin and discuss the factors involved in the formation and fine-tuning of bivalent domains. Finally, we examine how the deregulation of chromatin bivalency in the context of cancer could facilitate and/or reflect cancer cell adaptation. We propose a model in which bivalent chromatin represents a dynamic balance between otherwise opposing states, where the underlying DNA sequence is primed for the future activation or repression. Shifting this balance in any direction disrupts the tight equilibrium and tips cells into an altered epigenetic and phenotypic space, facilitating both developmental and cancer processes.
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Affiliation(s)
- Eleanor Glancy
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Natalie Choy
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Melanie A. Eckersley-Maslin
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
- Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria 3010, Australia
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6
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Ito S, Umehara T, Koseki H. Polycomb-mediated histone modifications and gene regulation. Biochem Soc Trans 2024; 52:151-161. [PMID: 38288743 DOI: 10.1042/bst20230336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 01/03/2024] [Accepted: 01/05/2024] [Indexed: 02/29/2024]
Abstract
Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) are transcriptional repressor complexes that play a fundamental role in epigenomic regulation and the cell-fate decision; these complexes are widely conserved in multicellular organisms. PRC1 is an E3 ubiquitin (ub) ligase that generates histone H2A ubiquitinated at lysine (K) 119 (H2AK119ub1), whereas PRC2 is a histone methyltransferase that specifically catalyzes tri-methylation of histone H3K27 (H3K27me3). Genome-wide analyses have confirmed that these two key epigenetic marks highly overlap across the genome and contribute to gene repression. We are now beginning to understand the molecular mechanisms that enable PRC1 and PRC2 to identify their target sites in the genome and communicate through feedback mechanisms to create Polycomb chromatin domains. Recently, it has become apparent that PRC1-induced H2AK119ub1 not only serves as a docking site for PRC2 but also affects the dynamics of the H3 tail, both of which enhance PRC2 activity, suggesting that trans-tail communication between H2A and H3 facilitates the formation of the Polycomb chromatin domain. In this review, we discuss the emerging principles that define how PRC1 and PRC2 establish the Polycomb chromatin domain and regulate gene expression in mammals.
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Affiliation(s)
- Shinsuke Ito
- Laboratory of Developmental Genetics, RIKEN Center for Integrative Medical Sciences, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Takashi Umehara
- Laboratory of Developmental Genetics, RIKEN Center for Integrative Medical Sciences, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
- Laboratory for Epigenetics Drug Discovery, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Haruhiko Koseki
- Laboratory of Developmental Genetics, RIKEN Center for Integrative Medical Sciences, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
- Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan
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7
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Li H, Playter C, Das P, McCord RP. Chromosome compartmentalization: causes, changes, consequences, and conundrums. Trends Cell Biol 2024:S0962-8924(24)00021-7. [PMID: 38395734 PMCID: PMC11339242 DOI: 10.1016/j.tcb.2024.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/12/2024] [Accepted: 01/22/2024] [Indexed: 02/25/2024]
Abstract
The spatial segregation of the genome into compartments is a major feature of 3D genome organization. New data on mammalian chromosome organization across different conditions reveal important information about how and why these compartments form and change. A combination of epigenetic state, nuclear body tethering, physical forces, gene expression, and replication timing (RT) can all influence the establishment and alteration of chromosome compartments. We review the causes and implications of genomic regions undergoing a 'compartment switch' that changes their physical associations and spatial location in the nucleus. About 20-30% of genomic regions change compartment during cell differentiation or cancer progression, whereas alterations in response to a stimulus within a cell type are usually much more limited. However, even a change in 1-2% of genomic bins may have biologically relevant implications. Finally, we review the effects of compartment changes on gene regulation, DNA damage repair, replication, and the physical state of the cell.
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Affiliation(s)
- Heng Li
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA
| | - Christopher Playter
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA
| | - Priyojit Das
- University of Tennessee-Oak Ridge National Laboratory (UT-ORNL) Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN, USA
| | - Rachel Patton McCord
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA.
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8
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Marie C, Scherman D. Antibiotic-Free Gene Vectors: A 25-Year Journey to Clinical Trials. Genes (Basel) 2024; 15:261. [PMID: 38540320 PMCID: PMC10970329 DOI: 10.3390/genes15030261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 02/07/2024] [Accepted: 02/15/2024] [Indexed: 06/15/2024] Open
Abstract
Until very recently, the major use, for gene therapy, specifically of linear or circular DNA, such as plasmids, was as ancillary products for viral vectors' production or as a genetic template for mRNA production. Thanks to targeted and more efficient physical or chemical delivery techniques and to the refinement of their structure, non-viral plasmid DNA are now under intensive consideration as pharmaceutical drugs. Plasmids traditionally carry an antibiotic resistance gene for providing the selection pressure necessary for maintenance in a bacterial host. Nearly a dozen different antibiotic-free gene vectors have now been developed and are currently assessed in preclinical assays and phase I/II clinical trials. Their reduced size leads to increased transfection efficiency and prolonged transgene expression. In addition, associating non-viral gene vectors and DNA transposons, which mediate transgene integration into the host genome, circumvents plasmid dilution in dividing eukaryotic cells which generate a loss of the therapeutic gene. Combining these novel molecular tools allowed a significantly higher yield of genetically engineered T and Natural Killer cells for adoptive immunotherapies due to a reduced cytotoxicity and increased transposition rate. This review describes the main progresses accomplished for safer, more efficient and cost-effective gene and cell therapies using non-viral approaches and antibiotic-free gene vectors.
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Affiliation(s)
- Corinne Marie
- Université Paris Cité, CNRS, Inserm, UTCBS, 75006 Paris, France;
- Chimie ParisTech, Université PSL, 75005 Paris, France
| | - Daniel Scherman
- Université Paris Cité, CNRS, Inserm, UTCBS, 75006 Paris, France;
- Fondation Maladies Rares, 75014 Paris, France
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9
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Del Vecchio A, Mulé P, Fernández-Pérez D, Amato S, Lattanzi G, Zanotti M, Rustichelli S, Pivetti S, Oldani P, Mariani A, Iommazzo F, Koseki H, Facciotti F, Tamburri S, Ferrari KJ, Pasini D. PCGF6 controls murine Tuft cell differentiation via H3K9me2 modification independently of Polycomb repression. Dev Cell 2024; 59:368-383.e7. [PMID: 38228142 DOI: 10.1016/j.devcel.2023.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 10/01/2023] [Accepted: 12/21/2023] [Indexed: 01/18/2024]
Abstract
Cell fate is determined by specific transcription programs that are essential for tissue homeostasis and regeneration. The E3-ligases RING1A and B represent the core activity of the Polycomb repressive complex 1 (PRC1) that deposits repressive histone H2AK119 mono-ubiquitination (H2AK119ub1), which is essential for mouse intestinal homeostasis by preserving stem cell functions. However, the specific role of different PRC1 forms, which are defined by the six distinct PCGF1-6 paralogs, remains largely unexplored in vivo. We report that PCGF6 regulates mouse intestinal Tuft cell differentiation independently of H2AK119ub1 deposition. We show that PCGF6 chromatin occupancy expands outside Polycomb repressive domains, associating with unique promoter and distal regulatory elements. This occurs in the absence of RING1A/B and involves MGA-mediated E-BOX recognition and specific H3K9me2 promoter deposition. PCGF6 inactivation induces an epithelial autonomous accumulation of Tuft cells that was not phenocopied by RING1A/B loss. This involves direct PCGF6 association with a Tuft cell differentiation program that identified Polycomb-independent properties of PCGF6 in adult tissues homeostasis.
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Affiliation(s)
- Annachiara Del Vecchio
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Patrizia Mulé
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Daniel Fernández-Pérez
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Simona Amato
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Georgia Lattanzi
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Marika Zanotti
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Samantha Rustichelli
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Silvia Pivetti
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Paola Oldani
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Andrea Mariani
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Fabiola Iommazzo
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Haruhiko Koseki
- RIKEN Centre for Integrative Medical Sciences, Laboratory for Developmental Genetics, 1-7-22 Suehiuro-cho, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Federica Facciotti
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy; University of Milano-Bicocca, Department of Biotechnology and Biosciences, Piazza della Scienza, 2, 20126 Milan, Italy
| | - Simone Tamburri
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy; University of Milan, Department of Health Sciences, Via A. di Rudinì 8, 20142 Milan, Italy
| | - Karin J Ferrari
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Diego Pasini
- IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Via Adamello 16, 20139 Milan, Italy; University of Milan, Department of Health Sciences, Via A. di Rudinì 8, 20142 Milan, Italy.
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10
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Liu J, Fan H, Liang X, Chen Y. Polycomb repressor complex: Its function in human cancer and therapeutic target strategy. Biomed Pharmacother 2023; 169:115897. [PMID: 37981459 DOI: 10.1016/j.biopha.2023.115897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/07/2023] [Accepted: 11/13/2023] [Indexed: 11/21/2023] Open
Abstract
The Polycomb Repressor Complex (PRC) plays a pivotal role in gene regulation during development and disease, with dysregulation contributing significantly to various human cancers. The intricate interplay between PRC and cellular signaling pathways sheds light on cancer complexity. PRC presents promising therapeutic opportunities, with inhibitors undergoing rigorous evaluation in preclinical and clinical studies. In this review, we emphasize the critical role of PRC complex in gene regulation, particularly PcG proteins mediated chromatin compaction through phase separation. We also highlight the pathological implications of PRC complex dysregulation in various tumors, elucidating underlying mechanisms driving cancer progression. The burgeoning field of therapeutic strategies targeting PRC complexes, notably EZH2 inhibitors, has advanced significantly. However, we explore the need for combination therapies to enhance PRC targeted treatments efficacy, providing a glimpse into the future of cancer therapeutics.
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Affiliation(s)
- Jingrong Liu
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China
| | - Hongjie Fan
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China
| | - Xinmiao Liang
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China; CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
| | - Yang Chen
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China; CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
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11
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Barrasa JI, Kahn TG, Lundkvist MJ, Schwartz YB. DNA elements tether canonical Polycomb Repressive Complex 1 to human genes. Nucleic Acids Res 2023; 51:11613-11633. [PMID: 37855680 PMCID: PMC10681801 DOI: 10.1093/nar/gkad889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 09/25/2023] [Accepted: 10/11/2023] [Indexed: 10/20/2023] Open
Abstract
Development of multicellular animals requires epigenetic repression by Polycomb group proteins. The latter assemble in multi-subunit complexes, of which two kinds, Polycomb Repressive Complex 1 (PRC1) and Polycomb Repressive Complex 2 (PRC2), act together to repress key developmental genes. How PRC1 and PRC2 recognize specific genes remains an open question. Here we report the identification of several hundreds of DNA elements that tether canonical PRC1 to human developmental genes. We use the term tether to describe a process leading to a prominent presence of canonical PRC1 at certain genomic sites, although the complex is unlikely to interact with DNA directly. Detailed analysis indicates that sequence features associated with PRC1 tethering differ from those that favour PRC2 binding. Throughout the genome, the two kinds of sequence features mix in different proportions to yield a gamut of DNA elements that range from those tethering predominantly PRC1 or PRC2 to ones capable of tethering both complexes. The emerging picture is similar to the paradigmatic targeting of Polycomb complexes by Polycomb Response Elements (PREs) of Drosophila but providing for greater plasticity.
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Affiliation(s)
- Juan I Barrasa
- Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden
| | - Tatyana G Kahn
- Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden
| | - Moa J Lundkvist
- Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden
| | - Yuri B Schwartz
- Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden
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12
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Hamali B, Amine AAA, Al-Sady B. Regulation of the heterochromatin spreading reaction by trans-acting factors. Open Biol 2023; 13:230271. [PMID: 37935357 PMCID: PMC10645111 DOI: 10.1098/rsob.230271] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 10/03/2023] [Indexed: 11/09/2023] Open
Abstract
Heterochromatin is a gene-repressive protein-nucleic acid ultrastructure that is initially nucleated by DNA sequences. However, following nucleation, heterochromatin can then propagate along the chromatin template in a sequence-independent manner in a reaction termed spreading. At the heart of this process are enzymes that deposit chemical information on chromatin, which attracts the factors that execute chromatin compaction and transcriptional or co/post-transcriptional gene silencing. Given that these enzymes deposit guiding chemical information on chromatin they are commonly termed 'writers'. While the processes of nucleation and central actions of writers have been extensively studied and reviewed, less is understood about how the spreading process is regulated. We discuss how the chromatin substrate is prepared for heterochromatic spreading, and how trans-acting factors beyond writer enzymes regulate it. We examine mechanisms by which trans-acting factors in Suv39, PRC2, SETDB1 and SIR writer systems regulate spreading of the respective heterochromatic marks across chromatin. While these systems are in some cases evolutionarily and mechanistically quite distant, common mechanisms emerge which these trans-acting factors exploit to tune the spreading reaction.
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Affiliation(s)
- Bulut Hamali
- Department of Microbiology and Immunology, University of California San Francisco, San Francisco, CA 94143, USA
- The G. W. Hooper Foundation, San Francisco, CA 94143, USA
- College of Dentistry, The Ohio State University, Columbus, OH, USA
| | - Ahmed A A Amine
- Department of Microbiology and Immunology, University of California San Francisco, San Francisco, CA 94143, USA
- The G. W. Hooper Foundation, San Francisco, CA 94143, USA
| | - Bassem Al-Sady
- Department of Microbiology and Immunology, University of California San Francisco, San Francisco, CA 94143, USA
- The G. W. Hooper Foundation, San Francisco, CA 94143, USA
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13
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Liu C, Wang Z, Wang J, Liu C, Wang M, Ngo V, Wang W. Predicting regional somatic mutation rates using DNA motifs. PLoS Comput Biol 2023; 19:e1011536. [PMID: 37782656 PMCID: PMC10569533 DOI: 10.1371/journal.pcbi.1011536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 10/12/2023] [Accepted: 09/20/2023] [Indexed: 10/04/2023] Open
Abstract
How the locus-specificity of epigenetic modifications is regulated remains an unanswered question. A contributing mechanism is that epigenetic enzymes are recruited to specific loci by DNA binding factors recognizing particular sequence motifs (referred to as epi-motifs). Using these motifs to predict biological outputs depending on local epigenetic state such as somatic mutation rates would confirm their functionality. Here, we used DNA motifs including known TF motifs and epi-motifs as a surrogate of epigenetic signals to predict somatic mutation rates in 13 cancers at an average 23kbp resolution. We implemented an interpretable neural network model, called contextual regression, to successfully learn the universal relationship between mutations and DNA motifs, and uncovered motifs that are most impactful on the regional mutation rates such as TP53 and epi-motifs associated with H3K9me3. Furthermore, we identified genomic regions with significantly higher mutation rates than the expected values in each individual tumor and demonstrated that such cancer-related regions can accurately predict cancer types. Interestingly, we found that the same mutation signatures often have different contributions to cancer-related and cancer-independent regions, and we also identified the motifs with the most contribution to each mutation signature.
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Affiliation(s)
- Cong Liu
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Zengmiao Wang
- State Key Laboratory of Remote Sensing Science, Center for Global Change and Public Health, Faculty of Geographical Science, Beijing Normal University, Beijing, China
| | - Jun Wang
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Chengyu Liu
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Mengchi Wang
- Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, California, United States of America
| | - Vu Ngo
- Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, California, United States of America
| | - Wei Wang
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
- Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, California, United States of America
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, United States of America
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14
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Sakamoto M, Abe S, Miki Y, Miyanari Y, Sasaki H, Ishiuchi T. Dynamic nucleosome remodeling mediated by YY1 underlies early mouse development. Genes Dev 2023; 37:590-604. [PMID: 37532472 PMCID: PMC10499016 DOI: 10.1101/gad.350376.122] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 07/12/2023] [Indexed: 08/04/2023]
Abstract
Nucleosome positioning can alter the accessibility of DNA-binding proteins to their cognate DNA elements, and thus its precise control is essential for cell identity and function. Mammalian preimplantation embryos undergo temporal changes in gene expression and cell potency, suggesting the involvement of dynamic epigenetic control during this developmental phase. However, the dynamics of nucleosome organization during early development are poorly understood. In this study, using a low-input MNase-seq method, we show that nucleosome positioning is globally obscure in zygotes but becomes well defined during subsequent development. Down-regulation of the chromatin assembly in embryonic stem cells can partially reverse nucleosome organization into a zygote-like pattern, suggesting a possible link between the chromatin assembly pathway and fuzzy nucleosomes in zygotes. We also reveal that YY1, a zinc finger-containing transcription factor expressed upon zygotic genome activation, regulates the de novo formation of well-positioned nucleosome arrays at the regulatory elements through identifying YY1-binding sites in eight-cell embryos. The YY1-binding regions acquire H3K27ac enrichment around the eight-cell and morula stages, and YY1 depletion impairs the morula-to-blastocyst transition. Thus, our study delineates the remodeling of nucleosome organization and its underlying mechanism during early mouse development.
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Affiliation(s)
- Mizuki Sakamoto
- Faculty of Life and Environmental Sciences, University of Yamanashi, Yamanashi 400-8510, Japan
| | - Shusaku Abe
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Yuka Miki
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Yusuke Miyanari
- NanoLSI, Cancer Research Institute, Kanazawa University, Kanazawa 920-1192, Japan
| | - Hiroyuki Sasaki
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Takashi Ishiuchi
- Faculty of Life and Environmental Sciences, University of Yamanashi, Yamanashi 400-8510, Japan;
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15
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Fischer S, Liefke R. Polycomb-like Proteins in Gene Regulation and Cancer. Genes (Basel) 2023; 14:genes14040938. [PMID: 37107696 PMCID: PMC10137883 DOI: 10.3390/genes14040938] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 04/14/2023] [Accepted: 04/17/2023] [Indexed: 04/29/2023] Open
Abstract
Polycomb-like proteins (PCLs) are a crucial group of proteins associated with the Polycomb repressive complex 2 (PRC2) and are responsible for setting up the PRC2.1 subcomplex. In the vertebrate system, three homologous PCLs exist: PHF1 (PCL1), MTF2 (PCL2), and PHF19 (PCL3). Although the PCLs share a similar domain composition, they differ significantly in their primary sequence. PCLs play a critical role in targeting PRC2.1 to its genomic targets and regulating the functionality of PRC2. However, they also have PRC2-independent functions. In addition to their physiological roles, their dysregulation has been associated with various human cancers. In this review, we summarize the current understanding of the molecular mechanisms of the PCLs and how alterations in their functionality contribute to cancer development. We particularly highlight the nonoverlapping and partially opposing roles of the three PCLs in human cancer. Our review provides important insights into the biological significance of the PCLs and their potential as therapeutic targets for cancer treatment.
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Affiliation(s)
- Sabrina Fischer
- Institute of Molecular Biology and Tumor Research (IMT), Philipps University of Marburg, 35043 Marburg, Germany
| | - Robert Liefke
- Institute of Molecular Biology and Tumor Research (IMT), Philipps University of Marburg, 35043 Marburg, Germany
- Department of Hematology, Oncology and Immunology, University Hospital Giessen and Marburg, 35043 Marburg, Germany
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16
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Komata Y, Kanai A, Maeda T, Inaba T, Yokoyama A. MOZ/ENL complex is a recruiting factor of leukemic AF10 fusion proteins. Nat Commun 2023; 14:1979. [PMID: 37031220 PMCID: PMC10082848 DOI: 10.1038/s41467-023-37712-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 03/22/2023] [Indexed: 04/10/2023] Open
Abstract
Changes in the transcriptional machinery cause aberrant self-renewal of non-stem hematopoietic progenitors. AF10 fusions, such as CALM-AF10, are generated via chromosomal translocations, causing malignant leukemia. In this study, we demonstrate that AF10 fusion proteins cause aberrant self-renewal via ENL, which binds to MOZ/MORF lysine acetyltransferases (KATs). The interaction of ENL with MOZ, via its YEATS domain, is critical for CALM-AF10-mediated leukemic transformation. The MOZ/ENL complex recruits DOT1L/AF10 fusion complexes and maintains their chromatin retention via KAT activity. Therefore, inhibitors of MOZ/MORF KATs directly suppress the functions of AF10 fusion proteins, thereby exhibiting strong antitumor effects on AF10 translocation-induced leukemia. Combinatorial inhibition of MOZ/MORF and DOT1L cooperatively induces differentiation of CALM-AF10-leukemia cells. These results reveal roles for the MOZ/ENL complex as an essential recruiting factor of the AF10 fusion/DOT1L complex, providing a rationale for using MOZ/MORF KAT inhibitors in AF10 translocation-induced leukemia.
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Affiliation(s)
- Yosuke Komata
- Tsuruoka Metabolomics Laboratory, National Cancer Center, Tsuruoka, Yamagata, 997-0052, Japan
| | - Akinori Kanai
- Laboratory of Systems Genomics, Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, the University of Tokyo, Kashiwa, Chiba, 277-0882, Japan
- Department of Molecular Oncology and Leukemia Program Project, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Hiroshima, 734-8553, Japan
| | - Takahiro Maeda
- Division of Precision Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka, Fukuoka, 812-8582, Japan
| | - Toshiya Inaba
- Department of Molecular Oncology and Leukemia Program Project, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Hiroshima, 734-8553, Japan
| | - Akihiko Yokoyama
- Tsuruoka Metabolomics Laboratory, National Cancer Center, Tsuruoka, Yamagata, 997-0052, Japan.
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17
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Fukushima HS, Takeda H, Nakamura R. Incomplete erasure of histone marks during epigenetic reprogramming in medaka early development. Genome Res 2023; 33:572-586. [PMID: 37117034 PMCID: PMC10234297 DOI: 10.1101/gr.277577.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 03/29/2023] [Indexed: 04/30/2023]
Abstract
Epigenetic modifications undergo drastic erasure and reestablishment after fertilization. This reprogramming is required for proper embryonic development and cell differentiation. In mammals, some histone modifications are not completely reprogrammed and play critical roles in later development. In contrast, in nonmammalian vertebrates, most histone modifications are thought to be more intensively erased and reestablished by the stage of zygotic genome activation (ZGA). However, histone modifications that escape reprogramming in nonmammalian vertebrates and their potential functional roles remain unknown. Here, we quantitatively and comprehensively analyzed histone modification dynamics during epigenetic reprogramming in Japanese killifish, medaka (Oryzias latipes) embryos. Our data revealed that H3K27ac, H3K27me3, and H3K9me3 escape complete reprogramming, whereas H3K4 methylation is completely erased during cleavage stage. Furthermore, we experimentally showed the functional roles of such retained modifications at early stages: (i) H3K27ac premarks promoters during the cleavage stage, and inhibition of histone acetyltransferases disrupts proper patterning of H3K4 and H3K27 methylation at CpG-dense promoters, but does not affect chromatin accessibility after ZGA; (ii) H3K9me3 is globally erased but specifically retained at telomeric regions, which is required for maintenance of genomic stability during the cleavage stage. These results expand the understanding of diversity and conservation of reprogramming in vertebrates, and unveil previously uncharacterized functions of histone modifications retained during epigenetic reprogramming.
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Affiliation(s)
- Hiroto S Fukushima
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hiroyuki Takeda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Ryohei Nakamura
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
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18
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Sparbier CE, Gillespie A, Gomez J, Kumari N, Motazedian A, Chan KL, Bell CC, Gilan O, Chan YC, Popp S, Gough DJ, Eckersley-Maslin MA, Dawson SJ, Lehner PJ, Sutherland KD, Ernst P, McGeehan GM, Lam EYN, Burr ML, Dawson MA. Targeting Menin disrupts the KMT2A/B and polycomb balance to paradoxically activate bivalent genes. Nat Cell Biol 2023; 25:258-272. [PMID: 36635503 PMCID: PMC7614190 DOI: 10.1038/s41556-022-01056-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/15/2022] [Indexed: 01/14/2023]
Abstract
Precise control of activating H3K4me3 and repressive H3K27me3 histone modifications at bivalent promoters is essential for normal development and frequently corrupted in cancer. By coupling a cell surface readout of bivalent MHC class I gene expression with whole-genome CRISPR-Cas9 screens, we identify specific roles for MTF2-PRC2.1, PCGF1-PRC1.1 and Menin-KMT2A/B complexes in maintaining bivalency. Genetic loss or pharmacological inhibition of Menin unexpectedly phenocopies the effects of polycomb disruption, resulting in derepression of bivalent genes in both cancer cells and pluripotent stem cells. While Menin and KMT2A/B contribute to H3K4me3 at active genes, a separate Menin-independent function of KMT2A/B maintains H3K4me3 and opposes polycomb-mediated repression at bivalent genes. Release of KMT2A from active genes following Menin targeting alters the balance of polycomb and KMT2A at bivalent genes, facilitating gene activation. This functional partitioning of Menin-KMT2A/B complex components reveals therapeutic opportunities that can be leveraged through inhibition of Menin.
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Affiliation(s)
- Christina E Sparbier
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Andrea Gillespie
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Juliana Gomez
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Nishi Kumari
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Ali Motazedian
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Kah Lok Chan
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
- Department of Clinical Haematology, Peter MacCallum Cancer Centre and Royal Melbourne Hospital, Melbourne, Victoria, Australia
| | - Charles C Bell
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Omer Gilan
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Australian Centre for Blood Diseases, Monash University, Melbourne, Victoria, Australia
| | - Yih-Chih Chan
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Sarah Popp
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Daniel J Gough
- Department of Molecular Translational Science, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Victoria, Australia
- Centre for Cancer Research, Hudson Institute of Medical Research, Clayton, Victoria, Australia
| | - Melanie A Eckersley-Maslin
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Sarah-Jane Dawson
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
- Centre for Cancer Research, University of Melbourne, Melbourne, Victoria, Australia
| | - Paul J Lehner
- Cambridge Institute of Therapeutic Immunology and Infectious Disease, Jeffrey Cheah Biomedical Centre, Cambridge Biomedical Campus, Cambridge, UK
| | - Kate D Sutherland
- ACRF Cancer Biology and Stem Cells Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Patricia Ernst
- Section of Hematology, Oncology and Bone Marrow Transplant, Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | | | - Enid Y N Lam
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Marian L Burr
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia.
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
- Department of Anatomical Pathology, ACT Pathology, Canberra Health Services, Canberra, Australian Capital Territory, Australia.
| | - Mark A Dawson
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia.
- Department of Clinical Haematology, Peter MacCallum Cancer Centre and Royal Melbourne Hospital, Melbourne, Victoria, Australia.
- Centre for Cancer Research, University of Melbourne, Melbourne, Victoria, Australia.
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19
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scChIX-seq infers dynamic relationships between histone modifications in single cells. Nat Biotechnol 2023:10.1038/s41587-022-01560-3. [PMID: 36593403 DOI: 10.1038/s41587-022-01560-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 10/12/2022] [Indexed: 01/03/2023]
Abstract
Regulation of chromatin states involves the dynamic interplay between different histone modifications to control gene expression. Recent advances have enabled mapping of histone marks in single cells, but most methods are constrained to profile only one histone mark per cell. Here, we present an integrated experimental and computational framework, scChIX-seq (single-cell chromatin immunocleavage and unmixing sequencing), to map several histone marks in single cells. scChIX-seq multiplexes two histone marks together in single cells, then computationally deconvolves the signal using training data from respective histone mark profiles. This framework learns the cell-type-specific correlation structure between histone marks, and therefore does not require a priori assumptions of their genomic distributions. Using scChIX-seq, we demonstrate multimodal analysis of histone marks in single cells across a range of mark combinations. Modeling dynamics of in vitro macrophage differentiation enables integrated analysis of chromatin velocity. Overall, scChIX-seq unlocks systematic interrogation of the interplay between histone modifications in single cells.
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20
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Regulation, functions and transmission of bivalent chromatin during mammalian development. Nat Rev Mol Cell Biol 2023; 24:6-26. [PMID: 36028557 DOI: 10.1038/s41580-022-00518-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/05/2022] [Indexed: 12/25/2022]
Abstract
Cells differentiate and progress through development guided by a dynamic chromatin landscape that mediates gene expression programmes. During development, mammalian cells display a paradoxical chromatin state: histone modifications associated with gene activation (trimethylated histone H3 Lys4 (H3K4me3)) and with gene repression (trimethylated H3 Lys27 (H3K27me3)) co-occur at promoters of developmental genes. This bivalent chromatin modification state is thought to poise important regulatory genes for expression or repression during cell-lineage specification. In this Review, we discuss recent work that has expanded our understanding of the molecular basis of bivalent chromatin and its contributions to mammalian development. We describe the factors that establish bivalency, especially histone-lysine N-methyltransferase 2B (KMT2B) and Polycomb repressive complex 2 (PRC2), and consider evidence indicating that PRC1 shapes bivalency and may contribute to its transmission between generations. We posit that bivalency is a key feature of germline and embryonic stem cells, as well as other types of stem and progenitor cells. Finally, we discuss the relevance of bivalent chromtin to human development and cancer, and outline avenues of future research.
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21
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Kim JJ, Kingston RE. Context-specific Polycomb mechanisms in development. Nat Rev Genet 2022; 23:680-695. [PMID: 35681061 PMCID: PMC9933872 DOI: 10.1038/s41576-022-00499-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/11/2022] [Indexed: 12/11/2022]
Abstract
Polycomb group (PcG) proteins are crucial chromatin regulators that maintain repression of lineage-inappropriate genes and are therefore required for stable cell fate. Recent advances show that PcG proteins form distinct multi-protein complexes in various cellular environments, such as in early development, adult tissue maintenance and cancer. This surprising compositional diversity provides the basis for mechanistic diversity. Understanding this complexity deepens and refines the principles of PcG complex recruitment, target-gene repression and inheritance of memory. We review how the core molecular mechanism of Polycomb complexes operates in diverse developmental settings and propose that context-dependent changes in composition and mechanism are essential for proper epigenetic regulation in development.
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Affiliation(s)
- Jongmin J. Kim
- Department of Molecular Biology and MGH Research Institute, Massachusetts General Hospital, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Robert E. Kingston
- Department of Molecular Biology and MGH Research Institute, Massachusetts General Hospital, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA.,
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22
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Scholl A, De S. Epigenetic Regulation by Polycomb Complexes from Drosophila to Human and Its Relation to Communicable Disease Pathogenesis. Int J Mol Sci 2022; 23:ijms232012285. [PMID: 36293135 PMCID: PMC9603650 DOI: 10.3390/ijms232012285] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 10/04/2022] [Accepted: 10/10/2022] [Indexed: 12/05/2022] Open
Abstract
Although all cells in the human body are made of the same DNA, these cells undergo differentiation and behave differently during development, through integration of external and internal stimuli via 'specific mechanisms.' Epigenetics is one such mechanism that comprises DNA/RNA, histone modifications, and non-coding RNAs that regulate transcription without changing the genetic code. The discovery of the first Polycomb mutant phenotype in Drosophila started the study of epigenetics more than 80 years ago. Since then, a considerable number of Polycomb Group (PcG) genes in Drosophila have been discovered to be preserved in mammals, including humans. PcG proteins exert their influence through gene repression by acting in complexes, modifying histones, and compacting the chromatin within the nucleus. In this article, we discuss how our knowledge of the PcG repression mechanism in Drosophila translates to human communicable disease research.
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23
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German B, Ellis L. Polycomb Directed Cell Fate Decisions in Development and Cancer. EPIGENOMES 2022; 6:28. [PMID: 36135315 PMCID: PMC9497807 DOI: 10.3390/epigenomes6030028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/01/2022] [Accepted: 09/01/2022] [Indexed: 11/16/2022] Open
Abstract
The polycomb group (PcG) proteins are a subset of transcription regulators highly conserved throughout evolution. Their principal role is to epigenetically modify chromatin landscapes and control the expression of master transcriptional programs to determine cellular identity. The two mayor PcG protein complexes that have been identified in mammals to date are Polycomb Repressive Complex 1 (PRC1) and 2 (PRC2). These protein complexes selectively repress gene expression via the induction of covalent post-translational histone modifications, promoting chromatin structure stabilization. PRC2 catalyzes the histone H3 methylation at lysine 27 (H3K27me1/2/3), inducing heterochromatin structures. This activity is controlled by the formation of a multi-subunit complex, which includes enhancer of zeste (EZH2), embryonic ectoderm development protein (EED), and suppressor of zeste 12 (SUZ12). This review will summarize the latest insights into how PRC2 in mammalian cells regulates transcription to orchestrate the temporal and tissue-specific expression of genes to determine cell identity and cell-fate decisions. We will specifically describe how PRC2 dysregulation in different cell types can promote phenotypic plasticity and/or non-mutational epigenetic reprogramming, inducing the development of highly aggressive epithelial neuroendocrine carcinomas, including prostate, small cell lung, and Merkel cell cancer. With this, EZH2 has emerged as an important actionable therapeutic target in such cancers.
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Affiliation(s)
- Beatriz German
- Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Leigh Ellis
- Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
- Cedars-Sinai Samuel Oschin Comprehensive Cancer Institute, Los Angeles, CA 90048, USA
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
- Center for Bioinformatics and Functional Genomics, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
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24
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Haq ZU, Saleem A, Khan AA, Dar MA, Ganaie AM, Beigh YA, Hamadani H, Ahmad SM. Nutrigenomics in livestock sector and its human-animal interface-a review. Vet Anim Sci 2022; 17:100262. [PMID: 35856004 PMCID: PMC9287789 DOI: 10.1016/j.vas.2022.100262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Nutrigenomics unfolds the link between nutrition and gene expression for productivity.expression profile of intramuscular. Nutrigenomics helps scientists discover genes and DNA in each animal's cell or tissue by assisting them in selecting nutrients. It brings out the importance of micronutrition for increasing animal production. Nutrigenomics integrates nutrition, molecular biology, genomics, bioinformatics, molecular medicine, and epidemiology.
Noncommunicable diseases such as cardiovascular disease, obesity, diabetes, and cancer now outnumber all other health ailments in humans globally due to abrupt changes in lifestyle following the industrial revolution. The industrial revolution has also intensified livestock farming, resulting in an increased demand for productivity and stressed animals. The livestock industry faces significant challenges from a projected sharp increase in global food and high animal protein demand. Nutrition genomics holds great promise for the future as its advances have opened up a whole new world of disease understanding and prevention. Nutrigenomics is the study of the interactions between genes and diet. It investigates molecular relationships between nutrients and genes to identify how even minor modifications could potentially alter animal and human health/performance by using techniques like proteomics, transcriptomics, metabolomics, and lipidomics. Dietary modifications mostly studied in livestock focus mainly on health and production traits through protein, fat, mineral, and vitamin supplementation changes. Nutrigenomics meticulously selects nutrients for fine-tuning the expression of genes that match animal/human genotypes for better health, productivity, and the environment. As a step forward, nutrigenomics integrates nutrition, molecular biology, genomics, bioinformatics, molecular medicine, and epidemiology to better understand the role of food as an epigenetic factor in the occurrence of these diseases. This review aims to provide a comprehensive overview of the fundamental concepts, latest advances, and studies in the field of nutrigenomics, emphasizing the interaction of diet with gene expression, and how it relates to human and animal health along with its human-animal interphase.
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25
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Verma A, Arya R, Brahmachari V. Identification of a polycomb responsive region in human HoxA cluster and its long-range interaction with polycomb enriched genomic regions. Gene 2022; 845:146832. [PMID: 36007803 DOI: 10.1016/j.gene.2022.146832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 08/15/2022] [Accepted: 08/18/2022] [Indexed: 11/04/2022]
Abstract
Polycomb and Trithorax group proteins (PcG, TrxG) epigenetically regulate developmental genes. These proteins bind with specific DNA elements, the Polycomb Response Element (PRE). Apart from mutations in polycomb/ trithorax proteins, altered cis-elements like PRE underlie the modified function and thus disease etiology. PREs are well studied in Drosophila, while only a few human PREs have been reported. We have identified a polycomb responsive DNA element, hPRE-HoxA3, in the intron of the HoxA3 gene. The hPRE-HoxA3 represses luciferase reporter activity in a PcG-dependent manner. The endogenous hPRE-HoxA3 element recruits PcG proteins and is enriched with repressive H3K27me3 marks, demonstrating that hPRE-HoxA3 is a part of the PcG-dependent gene regulatory network. Furthermore, it interacts with D11-12, the well-known PRE in the human Hox cluster. hPRE-Hox3 is a part of the 3-dimensional chromosomal domain organization as it is involved in the long-range interaction with other PcG enriched regions of Hox A, B, C, and D clusters.
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Affiliation(s)
- Akanksha Verma
- Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi-110007, India.
| | - Richa Arya
- Current address- Cytogenetics Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
| | - Vani Brahmachari
- Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi-110007, India
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26
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De Novo Polycomb Recruitment and Repressive Domain Formation. EPIGENOMES 2022; 6:epigenomes6030025. [PMID: 35997371 PMCID: PMC9397058 DOI: 10.3390/epigenomes6030025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 08/15/2022] [Accepted: 08/18/2022] [Indexed: 11/29/2022] Open
Abstract
Every cell of an organism shares the same genome; even so, each cellular lineage owns a different transcriptome and proteome. The Polycomb group proteins (PcG) are essential regulators of gene repression patterning during development and homeostasis. However, it is unknown how the repressive complexes, PRC1 and PRC2, identify their targets and elicit new Polycomb domains during cell differentiation. Classical recruitment models consider the pre-existence of repressive histone marks; still, de novo target binding overcomes the absence of both H3K27me3 and H2AK119ub. The CpG islands (CGIs), non-core proteins, and RNA molecules are involved in Polycomb recruitment. Nonetheless, it is unclear how de novo targets are identified depending on the physiological context and developmental stage and which are the leading players stabilizing Polycomb complexes at domain nucleation sites. Here, we examine the features of de novo sites and the accessory elements bridging its recruitment and discuss the first steps of Polycomb domain formation and transcriptional regulation, comprehended by the experimental reconstruction of the repressive domains through time-resolved genomic analyses in mammals.
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27
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Ng WS, Sielaff H, Zhao ZW. Phase Separation-Mediated Chromatin Organization and Dynamics: From Imaging-Based Quantitative Characterizations to Functional Implications. Int J Mol Sci 2022; 23:ijms23148039. [PMID: 35887384 PMCID: PMC9316379 DOI: 10.3390/ijms23148039] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 12/14/2022] Open
Abstract
As an effective and versatile strategy to compartmentalize cellular components without the need for lipid membranes, phase separation has been found to underpin a wide range of intranuclear processes, particularly those involving chromatin. Many of the unique physico-chemical properties of chromatin-based phase condensates are harnessed by the cell to accomplish complex regulatory functions in a spatially and temporally controlled manner. Here, we survey key recent findings on the mechanistic roles of phase separation in regulating the organization and dynamics of chromatin-based molecular processes across length scales, packing states and intranuclear functions, with a particular emphasis on quantitative characterizations of these condensates enabled by advanced imaging-based approaches. By illuminating the complex interplay between chromatin and various chromatin-interacting molecular species mediated by phase separation, this review sheds light on an emerging multi-scale, multi-modal and multi-faceted landscape that hierarchically regulates the genome within the highly crowded and dynamic nuclear space. Moreover, deficiencies in existing studies also highlight the need for mechanism-specific criteria and multi-parametric approaches for the characterization of chromatin-based phase separation using complementary techniques and call for greater efforts to correlate the quantitative features of these condensates with their functional consequences in close-to-native cellular contexts.
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Affiliation(s)
- Woei Shyuan Ng
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore 119543, Singapore; (W.S.N.); (H.S.)
- Centre for BioImaging Sciences (CBIS), Faculty of Science, National University of Singapore, Singapore 117557, Singapore
| | - Hendrik Sielaff
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore 119543, Singapore; (W.S.N.); (H.S.)
- Centre for BioImaging Sciences (CBIS), Faculty of Science, National University of Singapore, Singapore 117557, Singapore
| | - Ziqing Winston Zhao
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore 119543, Singapore; (W.S.N.); (H.S.)
- Centre for BioImaging Sciences (CBIS), Faculty of Science, National University of Singapore, Singapore 117557, Singapore
- Mechanobiology Institute (MBI), National University of Singapore, Singapore 117411, Singapore
- Correspondence:
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28
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Liu X, Liu X. PRC2, Chromatin Regulation, and Human Disease: Insights From Molecular Structure and Function. Front Oncol 2022; 12:894585. [PMID: 35800061 PMCID: PMC9255955 DOI: 10.3389/fonc.2022.894585] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 05/17/2022] [Indexed: 01/25/2023] Open
Abstract
Polycomb repressive complex 2 (PRC2) is a multisubunit histone-modifying enzyme complex that mediates methylation of histone H3 lysine 27 (H3K27). Trimethylated H3K27 (H3K27me3) is an epigenetic hallmark of gene silencing. PRC2 plays a crucial role in a plethora of fundamental biological processes, and PRC2 dysregulation has been repeatedly implicated in cancers and developmental disorders. Here, we review the current knowledge on mechanisms of cellular regulation of PRC2 function, particularly regarding H3K27 methylation and chromatin targeting. PRC2-related disease mechanisms are also discussed. The mode of action of PRC2 in gene regulation is summarized, which includes competition between H3K27 methylation and acetylation, crosstalk with transcription machinery, and formation of high-order chromatin structure. Recent progress in the structural biology of PRC2 is highlighted from the aspects of complex assembly, enzyme catalysis, and chromatin recruitment, which together provide valuable insights into PRC2 function in close-to-atomic detail. Future studies on the molecular function and structure of PRC2 in the context of native chromatin and in the presence of other regulators like RNAs will continue to deepen our understanding of the stability and plasticity of developmental transcriptional programs broadly impacted by PRC2.
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29
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Lowe MG, Yen MR, Hsu FM, Hosohama L, Hu Z, Chitiashvili T, Hunt TJ, Gorgy I, Bernard M, Wamaitha SE, Chen PY, Clark AT. EED is required for mouse primordial germ cell differentiation in the embryonic gonad. Dev Cell 2022; 57:1482-1495.e5. [PMID: 35679863 DOI: 10.1016/j.devcel.2022.05.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 12/14/2021] [Accepted: 05/16/2022] [Indexed: 11/18/2022]
Abstract
Development of primordial germ cells (PGCs) is required for reproduction. During PGC development in mammals, major epigenetic remodeling occurs, which is hypothesized to establish an epigenetic landscape for sex-specific germ cell differentiation and gametogenesis. In order to address the role of embryonic ectoderm development (EED) and histone 3 lysine 27 trimethylation (H3K27me3) in this process, we created an EED conditional knockout mouse and show that EED is essential for regulating the timing of sex-specific PGC differentiation in both ovaries and testes, as well as X chromosome dosage decompensation in testes. Integrating chromatin and whole genome bisulfite sequencing of epiblast and PGCs, we identified a poised repressive signature of H3K27me3/DNA methylation that we propose is established in the epiblast where EED and DNMT1 interact. Thus, EED joins DNMT1 in regulating the timing of sex-specific PGC differentiation during the critical window when the gonadal niche cells specialize into an ovary or testis.
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Affiliation(s)
- Matthew G Lowe
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA 90095, USA
| | - Ming-Ren Yen
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Fei-Man Hsu
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA 90095, USA
| | - Linzi Hosohama
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | - Zhongxun Hu
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | - Tsotne Chitiashvili
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA; Department of Biological Chemistry, University of California, Los Angeles, CA 90095, USA
| | - Timothy J Hunt
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | - Isaac Gorgy
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | - Matthew Bernard
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Sissy E Wamaitha
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | - Pao-Yang Chen
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Amander T Clark
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA 90095, USA; Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA 90095, USA.
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30
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Kraft K, Yost KE, Murphy SE, Magg A, Long Y, Corces MR, Granja JM, Wittler L, Mundlos S, Cech TR, Boettiger AN, Chang HY. Polycomb-mediated genome architecture enables long-range spreading of H3K27 methylation. Proc Natl Acad Sci U S A 2022; 119:e2201883119. [PMID: 35617427 PMCID: PMC9295753 DOI: 10.1073/pnas.2201883119] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 03/31/2022] [Indexed: 02/07/2023] Open
Abstract
Polycomb-group proteins play critical roles in gene silencing through the deposition of histone H3 lysine 27 trimethylation (H3K27me3) and chromatin compaction. This process is essential for embryonic stem cell (ESC) pluripotency, differentiation, and development. Polycomb repressive complex 2 (PRC2) can both read and write H3K27me3, enabling progressive spreading of H3K27me3 on the linear genome. Long-range Polycomb-associated DNA contacts have also been described, but their regulation and role in gene silencing remain unclear. Here, we apply H3K27me3 HiChIP, a protein-directed chromosome conformation method, and optical reconstruction of chromatin architecture to profile long-range Polycomb-associated DNA loops that span tens to hundreds of megabases across multiple topological associated domains in mouse ESCs and human induced pluripotent stem cells. We find that H3K27me3 loop anchors are enriched for Polycomb nucleation points and coincide with key developmental genes. Genetic deletion of H3K27me3 loop anchors results in disruption of spatial contact between distant loci and altered H3K27me3 in cis, both locally and megabases away on the same chromosome. In mouse embryos, loop anchor deletion leads to ectopic activation of the partner gene, suggesting that Polycomb-associated loops control gene silencing during development. Further, we find that alterations in PRC2 occupancy resulting from an RNA binding–deficient EZH2 mutant are accompanied by loss of Polycomb-associated DNA looping. Together, these results suggest PRC2 uses RNA binding to enhance long-range chromosome folding and H3K27me3 spreading. Developmental gene loci have unique roles in Polycomb spreading, emerging as important architectural elements of the epigenome.
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Affiliation(s)
- Katerina Kraft
- Center for Personal Dynamic Regulomes, Stanford University School of Medicine, Stanford, CA 94305
| | - Kathryn E. Yost
- Center for Personal Dynamic Regulomes, Stanford University School of Medicine, Stanford, CA 94305
| | | | - Andreas Magg
- Research Group of Development and Disease, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
- Institute for Medical and Human Genetics, Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Yicheng Long
- HHMI, University of Colorado, Boulder, CO 80309
- Department of Biochemistry, University of Colorado, Boulder, CO 80309
- BioFrontiers Institute, University of Colorado, Boulder, CO 80309
| | - M. Ryan Corces
- Center for Personal Dynamic Regulomes, Stanford University School of Medicine, Stanford, CA 94305
| | - Jeffrey M. Granja
- Center for Personal Dynamic Regulomes, Stanford University School of Medicine, Stanford, CA 94305
- Department of Genetics, Stanford University, Stanford, CA 94305
| | - Lars Wittler
- Department of Developmental Genetics, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Stefan Mundlos
- Research Group of Development and Disease, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
- Institute for Medical and Human Genetics, Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Thomas R. Cech
- HHMI, University of Colorado, Boulder, CO 80309
- Department of Biochemistry, University of Colorado, Boulder, CO 80309
- BioFrontiers Institute, University of Colorado, Boulder, CO 80309
| | | | - Howard Y. Chang
- Center for Personal Dynamic Regulomes, Stanford University School of Medicine, Stanford, CA 94305
- HHMI, Stanford University School of Medicine, Stanford, CA 94305
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31
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Tian H, He Y, Xue Y, Gao YQ. Expression regulation of genes is linked to their CpG density distributions around transcription start sites. Life Sci Alliance 2022; 5:5/9/e202101302. [PMID: 35580989 PMCID: PMC9113945 DOI: 10.26508/lsa.202101302] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 05/07/2022] [Accepted: 05/09/2022] [Indexed: 11/24/2022] Open
Abstract
The CpG dinucleotide and its methylation behaviors play vital roles in gene regulation. Previous studies have divided genes into several categories based on the CpG intensity around transcription starting sites and found that housekeeping genes tend to possess high CpG density, whereas tissue-specific genes are generally characterized by low CpG density. In this study, we investigated how the CpG density distribution of a gene affects its transcription and regulation pattern. Based on the CpG density distribution around transcription starting site, by means of a semi-supervised neural network we designed, which took data augmentation into account, we divided the human genes into three categories, and genes within each cluster shared similar CpG density distribution. Not only sequence properties, these different clusters exhibited distinctly different structural features, regulatory mechanisms, correlation patterns between the expression level and CpG/TpG density, and expression and epigenetic mark variations during tumorigenesis. For instance, the activation of cluster 3 genes relies more on 3D genome reorganization, compared with cluster 1 and 2 genes, whereas cluster 2 genes showed the strongest correlation between gene expression and H3K27me3. Genes exhibiting uncoupled correlation between gene regulation and histone modifications are mainly in cluster 3. These results emphasized that the usage of epigenetic marks in gene regulation is partially rooted in the sequence property of genes such as their CpG density distribution and explained to some extent why the relation between epigenetic marks and gene expression is controversial.
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Affiliation(s)
- Hao Tian
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Yueying He
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Yue Xue
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Yi Qin Gao
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China .,Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing, China.,Beijing Advanced Innovation Center for Genomics (ICG), Peking University, Beijing, China
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32
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Kori Y, Lund PJ, Trovato M, Sidoli S, Yuan ZF, Noh KM, Garcia BA. Multi-omic profiling of histone variant H3.3 lysine 27 methylation reveals a distinct role from canonical H3 in stem cell differentiation. Mol Omics 2022; 18:296-314. [PMID: 35044400 PMCID: PMC9098674 DOI: 10.1039/d1mo00352f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Histone variants, such as histone H3.3, replace canonical histones within the nucleosome to alter chromatin accessibility and gene expression. Although the biological roles of selected histone post-translational modifications (PTMs) have been extensively characterized, the potential differences in the function of a given PTM on different histone variants is almost always elusive. By applying proteomics and genomics techniques, we investigate the role of lysine 27 tri-methylation specifically on the histone variant H3.3 (H3.3K27me3) in the context of mouse embryonic stem cell pluripotency and differentiation as a model system for development. We demonstrate that while the steady state overall levels of methylation on both H3K27 and H3.3K27 decrease during differentiation, methylation dynamics studies indicate that methylation on H3.3K27 is maintained more than on H3K27. Using a custom-made antibody, we identify a unique enrichment of H3.3K27me3 at lineage-specific genes, such as olfactory receptor genes, and at binding motifs for the transcription factors FOXJ2/3. REST, a predicted FOXJ2/3 target that acts as a transcriptional repressor of terminal neuronal genes, was identified with H3.3K27me3 at its promoter region. H3.3K27A mutant cells confirmed an upregulation of FOXJ2/3 targets upon the loss of methylation at H3.3K27. Thus, while canonical H3K27me3 has been characterized to regulate the expression of transcription factors that play a general role in differentiation, our work suggests H3.3K27me3 is essential for regulating distinct terminal differentiation genes. This work highlights the importance of understanding the effects of PTMs not only on canonical histones but also on specific histone variants, as they may exhibit distinct roles.
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Affiliation(s)
- Yekaterina Kori
- Epigenetics Institute, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Peder J Lund
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
| | - Matteo Trovato
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
- Collaboration for Joint PhD Degree between EMBL and Heidelberg University, Faculty of Biosciences, Heidelberg, Germany
| | - Simone Sidoli
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Zuo-Fei Yuan
- Center for Proteomics and Metabolomics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Kyung-Min Noh
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Benjamin A Garcia
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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33
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Owen BM, Davidovich C. DNA binding by polycomb-group proteins: searching for the link to CpG islands. Nucleic Acids Res 2022; 50:4813-4839. [PMID: 35489059 PMCID: PMC9122586 DOI: 10.1093/nar/gkac290] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/25/2022] [Accepted: 04/25/2022] [Indexed: 11/13/2022] Open
Abstract
Polycomb group proteins predominantly exist in polycomb repressive complexes (PRCs) that cooperate to maintain the repressed state of thousands of cell-type-specific genes. Targeting PRCs to the correct sites in chromatin is essential for their function. However, the mechanisms by which PRCs are recruited to their target genes in mammals are multifactorial and complex. Here we review DNA binding by polycomb group proteins. There is strong evidence that the DNA-binding subunits of PRCs and their DNA-binding activities are required for chromatin binding and CpG targeting in cells. In vitro, CpG-specific binding was observed for truncated proteins externally to the context of their PRCs. Yet, the mere DNA sequence cannot fully explain the subset of CpG islands that are targeted by PRCs in any given cell type. At this time we find very little structural and biophysical evidence to support a model where sequence-specific DNA-binding activity is required or sufficient for the targeting of CpG-dinucleotide sequences by polycomb group proteins while they are within the context of their respective PRCs, either PRC1 or PRC2. We discuss the current knowledge and open questions on how the DNA-binding activities of polycomb group proteins facilitate the targeting of PRCs to chromatin.
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Affiliation(s)
- Brady M Owen
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia
| | - Chen Davidovich
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia.,EMBL-Australia, Clayton, VIC, Australia
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34
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O’Geen H, Tomkova M, Combs JA, Tilley EK, Segal D. Determinants of heritable gene silencing for KRAB-dCas9 + DNMT3 and Ezh2-dCas9 + DNMT3 hit-and-run epigenome editing. Nucleic Acids Res 2022; 50:3239-3253. [PMID: 35234927 PMCID: PMC8989539 DOI: 10.1093/nar/gkac123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 02/01/2022] [Accepted: 02/08/2022] [Indexed: 11/12/2022] Open
Abstract
Precision epigenome editing has gained significant attention as a method to modulate gene expression without altering genetic information. However, a major limiting factor has been that the gene expression changes are often transient, unlike the life-long epigenetic changes that occur frequently in nature. Here, we systematically interrogate the ability of CRISPR/dCas9-based epigenome editors (Epi-dCas9) to engineer persistent epigenetic silencing. We elucidated cis regulatory features that contribute to the differential stability of epigenetic reprogramming, such as the active transcription histone marks H3K36me3 and H3K27ac strongly correlating with resistance to short-term repression and resistance to long-term silencing, respectively. H3K27ac inversely correlates with increased DNA methylation. Interestingly, the dependance on H3K27ac was only observed when a combination of KRAB-dCas9 and targetable DNA methyltransferases (DNMT3A-dCas9 + DNMT3L) was used, but not when KRAB was replaced with the targetable H3K27 histone methyltransferase Ezh2. In addition, programmable Ezh2/DNMT3A + L treatment demonstrated enhanced engineering of localized DNA methylation and was not sensitive to a divergent chromatin state. Our results highlight the importance of local chromatin features for heritability of programmable silencing and the differential response to KRAB- and Ezh2-based epigenetic editing platforms. The information gained in this study provides fundamental insights into understanding contextual cues to more predictably engineer persistent silencing.
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Affiliation(s)
| | - Marketa Tomkova
- Genome Center, University of California, Davis, CA 95616, USA
| | | | - Emma K Tilley
- Genome Center, University of California, Davis, CA 95616, USA
| | - David J Segal
- Genome Center, University of California, Davis, CA 95616, USA
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616, USA
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35
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Parreno V, Martinez AM, Cavalli G. Mechanisms of Polycomb group protein function in cancer. Cell Res 2022; 32:231-253. [PMID: 35046519 PMCID: PMC8888700 DOI: 10.1038/s41422-021-00606-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 12/10/2021] [Indexed: 02/01/2023] Open
Abstract
Cancer arises from a multitude of disorders resulting in loss of differentiation and a stem cell-like phenotype characterized by uncontrolled growth. Polycomb Group (PcG) proteins are members of multiprotein complexes that are highly conserved throughout evolution. Historically, they have been described as essential for maintaining epigenetic cellular memory by locking homeotic genes in a transcriptionally repressed state. What was initially thought to be a function restricted to a few target genes, subsequently turned out to be of much broader relevance, since the main role of PcG complexes is to ensure a dynamically choregraphed spatio-temporal regulation of their numerous target genes during development. Their ability to modify chromatin landscapes and refine the expression of master genes controlling major switches in cellular decisions under physiological conditions is often misregulated in tumors. Surprisingly, their functional implication in the initiation and progression of cancer may be either dependent on Polycomb complexes, or specific for a subunit that acts independently of other PcG members. In this review, we describe how misregulated Polycomb proteins play a pleiotropic role in cancer by altering a broad spectrum of biological processes such as the proliferation-differentiation balance, metabolism and the immune response, all of which are crucial in tumor progression. We also illustrate how interfering with PcG functions can provide a powerful strategy to counter tumor progression.
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Affiliation(s)
- Victoria Parreno
- Institute of Human Genetics, UMR 9002, CNRS-University of Montpellier, Montpellier, France
| | - Anne-Marie Martinez
- Institute of Human Genetics, UMR 9002, CNRS-University of Montpellier, Montpellier, France.
| | - Giacomo Cavalli
- Institute of Human Genetics, UMR 9002, CNRS-University of Montpellier, Montpellier, France.
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36
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Fischer S, Weber LM, Liefke R. Evolutionary adaptation of the Polycomb repressive complex 2. Epigenetics Chromatin 2022; 15:7. [PMID: 35193659 PMCID: PMC8864842 DOI: 10.1186/s13072-022-00439-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Accepted: 02/08/2022] [Indexed: 12/31/2022] Open
Abstract
The Polycomb repressive complex 2 (PRC2) is an essential chromatin regulatory complex involved in repressing the transcription of diverse developmental genes. PRC2 consists of a core complex; possessing H3K27 methyltransferase activity and various associated factors that are important to modulate its function. During evolution, the composition of PRC2 and the functionality of PRC2 components have changed considerably. Here, we compare the PRC2 complex members of Drosophila and mammals and describe their adaptation to altered biological needs. We also highlight how the PRC2.1 subcomplex has gained multiple novel functions and discuss the implications of these changes for the function of PRC2 in chromatin regulation.
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Affiliation(s)
- Sabrina Fischer
- Institute of Molecular Biology and Tumor Research (IMT), Philipps University of Marburg, 35043, Marburg, Germany
| | - Lisa Marie Weber
- Institute of Molecular Biology and Tumor Research (IMT), Philipps University of Marburg, 35043, Marburg, Germany
| | - Robert Liefke
- Institute of Molecular Biology and Tumor Research (IMT), Philipps University of Marburg, 35043, Marburg, Germany. .,Department of Hematology, Oncology, and Immunology, University Hospital Giessen and Marburg, 35043, Marburg, Germany.
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37
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Du Y, Qian C. Non‐canonical bivalent H3K4me3K9me3 recognition by Spindlin1/C11orf84 complex. Bioessays 2022; 44:e2100229. [DOI: 10.1002/bies.202100229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 01/14/2022] [Accepted: 01/17/2022] [Indexed: 11/10/2022]
Affiliation(s)
- Yongming Du
- School of Biomedical Sciences The University of Hong Kong Pok Fu Lam Hong Kong
| | - Chengmin Qian
- School of Biomedical Sciences The University of Hong Kong Pok Fu Lam Hong Kong
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38
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Vijayanathan M, Trejo-Arellano MG, Mozgová I. Polycomb Repressive Complex 2 in Eukaryotes-An Evolutionary Perspective. EPIGENOMES 2022; 6:3. [PMID: 35076495 PMCID: PMC8788455 DOI: 10.3390/epigenomes6010003] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 01/12/2022] [Accepted: 01/12/2022] [Indexed: 12/23/2022] Open
Abstract
Polycomb repressive complex 2 (PRC2) represents a group of evolutionarily conserved multi-subunit complexes that repress gene transcription by introducing trimethylation of lysine 27 on histone 3 (H3K27me3). PRC2 activity is of key importance for cell identity specification and developmental phase transitions in animals and plants. The composition, biochemistry, and developmental function of PRC2 in animal and flowering plant model species are relatively well described. Recent evidence demonstrates the presence of PRC2 complexes in various eukaryotic supergroups, suggesting conservation of the complex and its function. Here, we provide an overview of the current understanding of PRC2-mediated repression in different representatives of eukaryotic supergroups with a focus on the green lineage. By comparison of PRC2 in different eukaryotes, we highlight the possible common and diverged features suggesting evolutionary implications and outline emerging questions and directions for future research of polycomb repression and its evolution.
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Affiliation(s)
- Mallika Vijayanathan
- Biology Centre, Institute of Plant Molecular Biology, Czech Academy of Sciences, 370 05 Ceske Budejovice, Czech Republic; (M.V.); (M.G.T.-A.)
| | - María Guadalupe Trejo-Arellano
- Biology Centre, Institute of Plant Molecular Biology, Czech Academy of Sciences, 370 05 Ceske Budejovice, Czech Republic; (M.V.); (M.G.T.-A.)
| | - Iva Mozgová
- Biology Centre, Institute of Plant Molecular Biology, Czech Academy of Sciences, 370 05 Ceske Budejovice, Czech Republic; (M.V.); (M.G.T.-A.)
- Faculty of Science, University of South Bohemia, 370 05 Ceske Budejovice, Czech Republic
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39
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Raposo AC, Casanova M, Gendrel AV, da Rocha ST. The tandem repeat modules of Xist lncRNA: a swiss army knife for the control of X-chromosome inactivation. Biochem Soc Trans 2021; 49:2549-2560. [PMID: 34882219 PMCID: PMC8786293 DOI: 10.1042/bst20210253] [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: 10/20/2021] [Revised: 11/19/2021] [Accepted: 11/23/2021] [Indexed: 12/16/2022]
Abstract
X-inactive-specific transcript (Xist) is a long non-coding RNA (lncRNA) essential for X-chromosome inactivation (XCI) in female placental mammals. Thirty years after its discovery, it is still puzzling how this lncRNA triggers major structural and transcriptional changes leading to the stable silencing of an entire chromosome. Recently, a series of studies in mouse cells have uncovered domains of functional specialization within Xist mapping to conserved tandem repeat regions, known as Repeats A-to-F. These functional domains interact with various RNA binding proteins (RBPs) and fold into distinct RNA structures to execute specific tasks in a synergistic and coordinated manner during the inactivation process. This modular organization of Xist is mostly conserved in humans, but recent data point towards differences regarding functional specialization of the tandem repeats between the two species. In this review, we summarize the recent progress on understanding the role of Xist repetitive blocks and their involvement in the molecular mechanisms underlying XCI. We also discuss these findings in the light of the similarities and differences between mouse and human Xist.
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Affiliation(s)
- Ana Cláudia Raposo
- Departamento de Bioengenharia e Instituto de Bioengenharia e Biociências, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Miguel Casanova
- Departamento de Bioengenharia e Instituto de Bioengenharia e Biociências, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Anne-Valerie Gendrel
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Simão Teixeira da Rocha
- Departamento de Bioengenharia e Instituto de Bioengenharia e Biociências, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
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40
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Kumar D, Cinghu S, Oldfield AJ, Yang P, Jothi R. Decoding the function of bivalent chromatin in development and cancer. Genome Res 2021; 31:2170-2184. [PMID: 34667120 PMCID: PMC8647824 DOI: 10.1101/gr.275736.121] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 10/15/2021] [Indexed: 12/12/2022]
Abstract
Bivalent chromatin is characterized by the simultaneous presence of H3K4me3 and H3K27me3, histone modifications generally associated with transcriptionally active and repressed chromatin, respectively. Prevalent in embryonic stem cells (ESCs), bivalency is postulated to poise/prime lineage-controlling developmental genes for rapid activation during embryogenesis while maintaining a transcriptionally repressed state in the absence of activation cues; however, this hypothesis remains to be directly tested. Most gene promoters DNA hypermethylated in adult human cancers are bivalently marked in ESCs, and it was speculated that bivalency predisposes them for aberrant de novo DNA methylation and irreversible silencing in cancer, but evidence supporting this model is largely lacking. Here, we show that bivalent chromatin does not poise genes for rapid activation but protects promoters from de novo DNA methylation. Genome-wide studies in differentiating ESCs reveal that activation of bivalent genes is no more rapid than that of other transcriptionally silent genes, challenging the premise that H3K4me3 is instructive for transcription. H3K4me3 at bivalent promoters-a product of the underlying DNA sequence-persists in nearly all cell types irrespective of gene expression and confers protection from de novo DNA methylation. Bivalent genes in ESCs that are frequent targets of aberrant hypermethylation in cancer are particularly strongly associated with loss of H3K4me3/bivalency in cancer. Altogether, our findings suggest that bivalency protects reversibly repressed genes from irreversible silencing and that loss of H3K4me3 may make them more susceptible to aberrant DNA methylation in diseases such as cancer. Bivalency may thus represent a distinct regulatory mechanism for maintaining epigenetic plasticity.
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Affiliation(s)
- Dhirendra Kumar
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | - Senthilkumar Cinghu
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | - Andrew J Oldfield
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | - Pengyi Yang
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | - Raja Jothi
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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41
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Blackledge NP, Klose RJ. The molecular principles of gene regulation by Polycomb repressive complexes. Nat Rev Mol Cell Biol 2021; 22:815-833. [PMID: 34400841 PMCID: PMC7612013 DOI: 10.1038/s41580-021-00398-y] [Citation(s) in RCA: 181] [Impact Index Per Article: 60.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2021] [Indexed: 12/12/2022]
Abstract
Precise control of gene expression is fundamental to cell function and development. Although ultimately gene expression relies on DNA-binding transcription factors to guide the activity of the transcription machinery to genes, it has also become clear that chromatin and histone post-translational modification have fundamental roles in gene regulation. Polycomb repressive complexes represent a paradigm of chromatin-based gene regulation in animals. The Polycomb repressive system comprises two central protein complexes, Polycomb repressive complex 1 (PRC1) and PRC2, which are essential for normal gene regulation and development. Our early understanding of Polycomb function relied on studies in simple model organisms, but more recently it has become apparent that this system has expanded and diverged in mammals. Detailed studies are now uncovering the molecular mechanisms that enable mammalian PRC1 and PRC2 to identify their target sites in the genome, communicate through feedback mechanisms to create Polycomb chromatin domains and control transcription to regulate gene expression. In this Review, we discuss and contextualize the emerging principles that define how this fascinating chromatin-based system regulates gene expression in mammals.
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Affiliation(s)
| | - Robert J Klose
- Department of Biochemistry, University of Oxford, Oxford, UK.
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42
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Holoch D, Wassef M, Lövkvist C, Zielinski D, Aflaki S, Lombard B, Héry T, Loew D, Howard M, Margueron R. A cis-acting mechanism mediates transcriptional memory at Polycomb target genes in mammals. Nat Genet 2021; 53:1686-1697. [PMID: 34782763 DOI: 10.1038/s41588-021-00964-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 10/05/2021] [Indexed: 11/09/2022]
Abstract
Epigenetic inheritance of gene expression states enables a single genome to maintain distinct cellular identities. How histone modifications contribute to this process remains unclear. Using global chromatin perturbations and local, time-controlled modulation of transcription, we establish the existence of epigenetic memory of transcriptional activation for genes that can be silenced by the Polycomb group. This property emerges during cell differentiation and allows genes to be stably switched after a transient transcriptional stimulus. This transcriptional memory state at Polycomb targets operates in cis; however, rather than relying solely on read-and-write propagation of histone modifications, the memory is also linked to the strength of activating inputs opposing Polycomb proteins, and therefore varies with the cellular context. Our data and computational simulations suggest a model whereby transcriptional memory arises from double-negative feedback between Polycomb-mediated silencing and active transcription. Transcriptional memory at Polycomb targets thus depends not only on histone modifications but also on the gene-regulatory network and underlying identity of a cell.
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Affiliation(s)
- Daniel Holoch
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Michel Wassef
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Cecilia Lövkvist
- John Innes Centre, Norwich Research Park, Norwich, UK. .,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
| | - Dina Zielinski
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France.,INSERM U900, Mines ParisTech, Paris, France
| | - Setareh Aflaki
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Bérangère Lombard
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,Proteomics Mass Spectrometry Laboratory, Paris, France
| | - Tiphaine Héry
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Damarys Loew
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,Proteomics Mass Spectrometry Laboratory, Paris, France
| | - Martin Howard
- John Innes Centre, Norwich Research Park, Norwich, UK
| | - Raphaël Margueron
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France. .,INSERM U934/CNRS UMR 3215, Paris, France.
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43
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Sex-specific chromatin remodelling safeguards transcription in germ cells. Nature 2021; 600:737-742. [PMID: 34880491 DOI: 10.1038/s41586-021-04208-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 11/01/2021] [Indexed: 11/08/2022]
Abstract
Stability of the epigenetic landscape underpins maintenance of the cell-type-specific transcriptional profile. As one of the main repressive epigenetic systems, DNA methylation has been shown to be important for long-term gene silencing; its loss leads to ectopic and aberrant transcription in differentiated cells and cancer1. The developing mouse germ line endures global changes in DNA methylation in the absence of widespread transcriptional activation. Here, using an ultra-low-input native chromatin immunoprecipitation approach, we show that following DNA demethylation the gonadal primordial germ cells undergo remodelling of repressive histone modifications, resulting in a sex-specific signature in mice. We further demonstrate that Polycomb has a central role in transcriptional control in the newly hypomethylated germline genome as the genetic loss of Ezh2 leads to aberrant transcriptional activation, retrotransposon derepression and dramatic loss of developing female germ cells. This sex-specific effect of Ezh2 deletion is explained by the distinct landscape of repressive modifications observed in male and female germ cells. Overall, our study provides insight into the dynamic interplay between repressive chromatin modifications in the context of a developmental reprogramming system.
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44
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Structural insights into the interactions of Polycomb Repressive Complex 2 with chromatin. Biochem Soc Trans 2021; 49:2639-2653. [PMID: 34747969 DOI: 10.1042/bst20210450] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/21/2021] [Accepted: 10/18/2021] [Indexed: 12/12/2022]
Abstract
Polycomb repressive complexes are a family of chromatin modifier enzymes which are critical for regulating gene expression and maintaining cell-type identity. The reversible chemical modifications of histone H3 and H2A by the Polycomb proteins are central to its ability to function as a gene silencer. PRC2 is both a reader and writer of the tri-methylation of histone H3 lysine 27 (H3K27me3) which serves as a marker for transcription repression, and heterochromatin boundaries. Over the last few years, several studies have provided key insights into the mechanisms regulating the recruitment and activation of PRC2 at Polycomb target genes. In this review, we highlight the recent structural studies which have elucidated the roles played by Polycomb cofactor proteins in mediating crosstalk between histone post-translational modifications and the recruitment of PRC2 and the stimulation of PRC2 methyltransferase activity.
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45
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Park SH, Fong KW, Mong E, Martin MC, Schiltz GE, Yu J. Going beyond Polycomb: EZH2 functions in prostate cancer. Oncogene 2021; 40:5788-5798. [PMID: 34349243 PMCID: PMC8487936 DOI: 10.1038/s41388-021-01982-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 07/20/2021] [Accepted: 07/22/2021] [Indexed: 02/07/2023]
Abstract
The Polycomb group (PcG) protein Enhancer of Zeste Homolog 2 (EZH2) is one of the three core subunits of the Polycomb Repressive Complex 2 (PRC2). It harbors histone methyltransferase activity (MTase) that specifically catalyze histone 3 lysine 27 (H3K27) methylation on target gene promoters. As such, PRC2 are epigenetic silencers that play important roles in cellular identity and embryonic stem cell maintenance. In the past two decades, mounting evidence supports EZH2 mutations and/or over-expression in a wide array of hematological cancers and solid tumors, including prostate cancer. Further, EZH2 is among the most upregulated genes in neuroendocrine prostate cancers, which become abundant due to the clinical use of high-affinity androgen receptor pathway inhibitors. While numerous studies have reported epigenetic functions of EZH2 that inhibit tumor suppressor genes and promote tumorigenesis, discordance between EZH2 and H3K27 methylation has been reported. Further, enzymatic EZH2 inhibitors have shown limited efficacy in prostate cancer, warranting a more comprehensive understanding of EZH2 functions. Here we first review how canonical functions of EZH2 as a histone MTase are regulated and describe the various mechanisms of PRC2 recruitment to the chromatin. We further outline non-histone substrates of EZH2 and discuss post-translational modifications to EZH2 itself that may affect substrate preference. Lastly, we summarize non-canonical functions of EZH2, beyond its MTase activity and/or PRC2, as a transcriptional cofactor and discuss prospects of its therapeutic targeting in prostate cancer.
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Affiliation(s)
- Su H Park
- Division of Hematology/Oncology, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Ka-Wing Fong
- Division of Hematology/Oncology, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, KY, USA
| | - Ezinne Mong
- Division of Hematology/Oncology, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - M Cynthia Martin
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Gary E Schiltz
- Department of Chemistry, Northwestern University, Evanston, IL, USA
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL, USA
| | - Jindan Yu
- Division of Hematology/Oncology, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL, USA.
- Department of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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46
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Baile F, Merini W, Hidalgo I, Calonje M. EAR domain-containing transcription factors trigger PRC2-mediated chromatin marking in Arabidopsis. THE PLANT CELL 2021; 33:2701-2715. [PMID: 34003929 PMCID: PMC8408475 DOI: 10.1093/plcell/koab139] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 05/14/2021] [Indexed: 05/22/2023]
Abstract
Polycomb group (PcG) complexes ensure that every cell in an organism expresses the genes needed at a particular stage, time, or condition. However, it is still not fully understood how PcG complexes PcG-repressive complex 1 (PRC1) and PRC2 are recruited to target genes in plants. Recent findings in Arabidopsis thaliana support the notion that PRC2 recruitment is mediated by different transcription factors (TFs). However, it is unclear how all these TFs interact with PRC2 and whether they also recruit PRC1 activity. Here, by using a system to bind selected TFs to a synthetic promoter lacking the complexity of PcG target promoters in vivo, we show that while binding of the TF VIVIPAROUS1/ABSCISIC ACID-INSENSITIVE3-LIKE1 recapitulates PRC1 and PRC2 marking, the binding of other TFs only renders PRC2 marking. Interestingly, all these TFs contain an Ethylene-responsive element binding factor-associated Amphiphilic Repression (EAR) domain that triggers both HISTONE DEACETYLASE COMPLEX and PRC2 activities, connecting two different repressive mechanisms. Furthermore, we show that different TFs can have an additive effect on PRC2 activity, which may be required to maintain long-term repression of gene expression.
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Affiliation(s)
- Fernando Baile
- Institute of Plant Biochemistry and Photosynthesis (IBVF-CSIC-US), Avenida Américo Vespucio 49, 41092, Seville, Spain
| | - Wiam Merini
- Institute of Plant Biochemistry and Photosynthesis (IBVF-CSIC-US), Avenida Américo Vespucio 49, 41092, Seville, Spain
| | - Inés Hidalgo
- Institute of Plant Biochemistry and Photosynthesis (IBVF-CSIC-US), Avenida Américo Vespucio 49, 41092, Seville, Spain
| | - Myriam Calonje
- Institute of Plant Biochemistry and Photosynthesis (IBVF-CSIC-US), Avenida Américo Vespucio 49, 41092, Seville, Spain
- Author for correspondence:
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47
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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.
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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.
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48
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Zhang C, Macchi F, Magnani E, Sadler KC. Chromatin states shaped by an epigenetic code confer regenerative potential to the mouse liver. Nat Commun 2021; 12:4110. [PMID: 34226551 PMCID: PMC8257577 DOI: 10.1038/s41467-021-24466-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 06/10/2021] [Indexed: 02/06/2023] Open
Abstract
We hypothesized that the highly controlled pattern of gene expression that is essential for liver regeneration is encoded by an epigenetic code set in quiescent hepatocytes. Here we report that epigenetic and transcriptomic profiling of quiescent and regenerating mouse livers define chromatin states that dictate gene expression and transposon repression. We integrate ATACseq and DNA methylation profiling with ChIPseq for the histone marks H3K4me3, H3K27me3 and H3K9me3 and the histone variant H2AZ to identify 6 chromatin states with distinct functional characteristics. We show that genes involved in proliferation reside in active states, but are marked with H3K27me3 and silenced in quiescent livers. We find that during regeneration, H3K27me3 is depleted from their promoters, facilitating their dynamic expression. These findings demonstrate that hepatic chromatin states in quiescent livers predict gene expression and that pro-regenerative genes are maintained in active chromatin states, but are restrained by H3K27me3, permitting a rapid and synchronized response during regeneration.
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Affiliation(s)
- Chi Zhang
- grid.440573.1Biology Program, NYU Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Filippo Macchi
- grid.440573.1Biology Program, NYU Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Elena Magnani
- grid.440573.1Biology Program, NYU Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Kirsten C. Sadler
- grid.440573.1Biology Program, NYU Abu Dhabi, Abu Dhabi, United Arab Emirates
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49
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Lambrot R, Chan D, Shao X, Aarabi M, Kwan T, Bourque G, Moskovtsev S, Librach C, Trasler J, Dumeaux V, Kimmins S. Whole-genome sequencing of H3K4me3 and DNA methylation in human sperm reveals regions of overlap linked to fertility and development. Cell Rep 2021; 36:109418. [PMID: 34289352 DOI: 10.1016/j.celrep.2021.109418] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 02/12/2021] [Accepted: 06/28/2021] [Indexed: 12/19/2022] Open
Abstract
The paternal environment has been linked to infertility and negative outcomes. Such effects may be transmitted via sperm through histone modifications. To date, in-depth profiling of the sperm chromatin in men has been limited. Here, we use deep sequencing to characterize the sperm profiles of histone H3 lysine 4 tri-methylation (H3K4me3) and DNA methylation in a representative reference population of 37 men. Our analysis reveals that H3K4me3 is localized throughout the genome and at genes for fertility and development. Remarkably, enrichment is also found at regions that escape epigenetic reprogramming in primordial germ cells, embryonic enhancers, and short-interspersed nuclear elements (SINEs). There is significant overlap in H3K4me3 and DNA methylation throughout the genome, suggesting a potential interplay between these marks previously reported to be mutually exclusive in sperm. Comparisons made between H3K4me3 marked regions in sperm and the embryonic transcriptome suggest an influence of paternal chromatin on embryonic gene expression.
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Affiliation(s)
- Romain Lambrot
- Department of Animal Science, McGill University, Montreal, QC, Canada
| | - Donovan Chan
- Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Xiaojian Shao
- Digital Technologies Research Centre, National Research Council, Ottawa, ON, Canada
| | - Mahmoud Aarabi
- Department of Laboratory Medicine and Pathobiology, North York General Hospital, University of Toronto, Toronto, ON, Canada; Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Tony Kwan
- Human Genetics, McGill University, Montreal, QC, Canada
| | | | - Sergey Moskovtsev
- CReATe Fertility Centre, Toronto, ON, Canada; Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON, Canada
| | - Clifford Librach
- CReATe Fertility Centre, Toronto, ON, Canada; Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON, Canada
| | - Jacquetta Trasler
- Research Institute of the McGill University Health Centre, Montreal, QC, Canada; Human Genetics, McGill University, Montreal, QC, Canada; Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada; Department of Pediatrics, McGill University, Montreal, QC, Canada
| | - Vanessa Dumeaux
- PERFORM Center, Concordia University, Montreal, QC, Canada; Department of Biology, Concordia University, Montreal, QC, Canada.
| | - Sarah Kimmins
- Department of Animal Science, McGill University, Montreal, QC, Canada; Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada.
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50
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Ghotbi E, Ye P, Ervin T, Kum A, Benes J, Jones RS. Polycomb-group recruitment to a Drosophila target gene is the default state that is inhibited by a transcriptional activator. SCIENCE ADVANCES 2021; 7:7/29/eabg1556. [PMID: 34272248 PMCID: PMC8284896 DOI: 10.1126/sciadv.abg1556] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 05/25/2021] [Indexed: 06/13/2023]
Abstract
Polycomb-group (PcG) proteins are epigenetic regulators that maintain the transcriptional repression of target genes following their initial repression by transcription factors. PcG target genes are repressed in some cells, but active in others. Therefore, a mechanism must exist by which PcG proteins distinguish between the repressed and active states and only assemble repressive chromatin environments at target genes that are repressed. Here, we present experimental evidence that the repressed state of a Drosophila PcG target gene, giant (gt), is not identified by the presence of a repressor. Rather, de novo establishment of PcG-mediated silencing at gt is the default state that is prevented by the presence of an activator or coactivator, which may inhibit the catalytic activity of Polycomb-repressive complex 2 (PRC2).
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Affiliation(s)
- Elnaz Ghotbi
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Piao Ye
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Taylor Ervin
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Anni Kum
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Judith Benes
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Richard S Jones
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA.
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