1
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Lv J, Chen Q, Wang J, Guo N, Fang Y, Guo Q, Li J, Ma X, Zhan H, Chen W, Wang L, Yan Q, Tong J, Wang Z. Downregulation of MLF1 safeguards cardiomyocytes against senescence-associated chromatin opening. Nucleic Acids Res 2024:gkae1176. [PMID: 39657728 DOI: 10.1093/nar/gkae1176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 10/21/2024] [Accepted: 11/12/2024] [Indexed: 12/12/2024] Open
Abstract
Aging-associated cardiac hypertrophy (AACH) increases susceptibility to heart failure in the elderly. Chromatin remodeling contributes to the gene reprogramming in AACH; however, the intrinsic regulations remain elusive. We performed a transcriptome analysis for AACH in comparison with pressure-overload-induced pathological cardiac hypertrophy in mice and identified myeloid leukemia factor 1 (MLF1) as an aging-sensitive factor whose expression was reduced during aging but could be reversed by anti-aging administrations. In human AC16 cardiomyocytes, silencing MLF1 suppressed H2O2-induced cell senescence while the phenotype was exacerbated by MLF1 overexpression. RNA-seq analysis revealed that MLF1 functioned as a transcription activator, regulating genomic-clustered genes that mainly involved in inflammation and development. ATAC-seq analysis showed a prominent reduction in chromatin accessibility at the promoter regions of senescence effectors, like IL1B and p21, after MLF1 knockdown. Despite a potential interaction of MLF1 with the histone methyltransferase PRC2, its inhibition failed to reverse the impact of MLF1 knockdown. Instead, MLF1-mediated regulation was blunted by inhibiting the acetyltransferase EP300. CUT&Tag analysis showed that MLF1 bound to target promoters and recruited EP300 to promote H3K27ac deposition. Collectively, we identify MLF1 as a pro-aging epigenetic orchestrator that recruits EP300 to facilitate opening of the condensed chromatin encompassing senescence effectors.
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Affiliation(s)
- Jian Lv
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Qin Chen
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
- School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Junmei Wang
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
| | - Ningning Guo
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Yu Fang
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China
| | - Qiuxiao Guo
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
| | - Jiajie Li
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
| | - Xiao Ma
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China
| | - Hongchao Zhan
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
| | - Weihao Chen
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
| | - Li Wang
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China
| | - Qingqing Yan
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China
| | - Jingjing Tong
- School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Zhihua Wang
- Shenzhen Key Laboratory of Cardiovascular Disease, Fuwai Shenzhen Hospital, Chinese Academy of Medical Sciences, Shenzhen 518057, China
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China
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2
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Sauer PV, Pavlenko E, Cookis T, Zirden LC, Renn J, Singhal A, Hunold P, Hoehne-Wiechmann MN, van Ray O, Kaschani F, Kaiser M, Hänsel-Hertsch R, Sanbonmatsu KY, Nogales E, Poepsel S. Activation of automethylated PRC2 by dimerization on chromatin. Mol Cell 2024; 84:3885-3898.e8. [PMID: 39303719 DOI: 10.1016/j.molcel.2024.08.025] [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: 05/31/2024] [Accepted: 08/21/2024] [Indexed: 09/22/2024]
Abstract
Polycomb repressive complex 2 (PRC2) is an epigenetic regulator that trimethylates lysine 27 of histone 3 (H3K27me3) and is essential for embryonic development and cellular differentiation. H3K27me3 is associated with transcriptionally repressed chromatin and is established when PRC2 is allosterically activated upon methyl-lysine binding by the regulatory subunit EED. Automethylation of the catalytic subunit enhancer of zeste homolog 2 (EZH2) stimulates its activity by an unknown mechanism. Here, we show that human PRC2 forms a dimer on chromatin in which an inactive, automethylated PRC2 protomer is the allosteric activator of a second PRC2 that is poised to methylate H3 of a substrate nucleosome. Functional assays support our model of allosteric trans-autoactivation via EED, suggesting a previously unknown mechanism mediating context-dependent activation of PRC2. Our work showcases the molecular mechanism of auto-modification-coupled dimerization in the regulation of chromatin-modifying complexes.
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Affiliation(s)
- Paul V Sauer
- California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
| | - Egor Pavlenko
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany
| | - Trinity Cookis
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Linda C Zirden
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany
| | - Juliane Renn
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany
| | - Ankush Singhal
- Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Pascal Hunold
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany; Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Michaela N Hoehne-Wiechmann
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany; Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Olivia van Ray
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany; Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Farnusch Kaschani
- Department of Chemical Biology, University of Duisburg-Essen, Center for Medical Biotechnology (ZMB), Faculty of Biology, Essen, Germany
| | - Markus Kaiser
- Department of Chemical Biology, University of Duisburg-Essen, Center for Medical Biotechnology (ZMB), Faculty of Biology, Essen, Germany
| | - Robert Hänsel-Hertsch
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany; Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany; Institute of Human Genetics, University Hospital Cologne, 50931 Cologne, Germany; Cologne Excellence Cluster for Cellular Stress Responses in Ageing-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Karissa Y Sanbonmatsu
- Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Eva Nogales
- California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA; Molecular Biophysics and Integrative Bio-Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
| | - Simon Poepsel
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, 50931 Cologne, Germany; Cologne Excellence Cluster for Cellular Stress Responses in Ageing-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany.
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3
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Poltronieri P. Regulatory RNAs: role as scaffolds assembling protein complexes and their epigenetic deregulation. EXPLORATION OF TARGETED ANTI-TUMOR THERAPY 2024; 5:841-876. [PMID: 39280246 PMCID: PMC11390297 DOI: 10.37349/etat.2024.00252] [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: 01/30/2024] [Accepted: 04/26/2024] [Indexed: 09/18/2024] Open
Abstract
Recently, new data have been added to the interaction between non-coding RNAs (ncRNAs) and epigenetic machinery. Epigenetics includes enzymes involved in DNA methylation, histone modifications, and RNA modifications, and mechanisms underlying chromatin structure, repressive states, and active states operating in transcription. The main focus is on long ncRNAs (lncRNAs) acting as scaffolds to assemble protein complexes. This review does not cover RNA's role in sponging microRNAs, or decoy functions. Several lncRNAs were shown to regulate chromatin activation and repression by interacting with Polycomb repressive complexes and mixed-lineage leukemia (MLL) activating complexes. Various groups reported on enhancer of zeste homolog 2 (EZH2) interactions with regulatory RNAs. Knowledge of the function of these complexes opens the perspective to develop new therapeutics for cancer treatment. Lastly, the interplay between lncRNAs and epitranscriptomic modifications in cancers paves the way for new targets in cancer therapy. The approach to inhibit lncRNAs interaction with protein complexes and perspective to regulate epitrascriptomics-regulated RNAs may bring new compounds as therapeuticals in various types of cancer.
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Affiliation(s)
- Palmiro Poltronieri
- Agrofood Department, National Research Council, CNR-ISPA, 73100 Lecce, Italy
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4
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Ciapponi M, Karlukova E, Schkölziger S, Benda C, Müller J. Structural basis of the histone ubiquitination read-write mechanism of RYBP-PRC1. Nat Struct Mol Biol 2024; 31:1023-1027. [PMID: 38528151 PMCID: PMC11257959 DOI: 10.1038/s41594-024-01258-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 02/26/2024] [Indexed: 03/27/2024]
Abstract
Histone H2A monoubiquitination (H2Aub1) by the PRC1 subunit RING1B entails a positive feedback loop, mediated by the RING1B-interacting protein RYBP. We uncover that human RYBP-PRC1 binds unmodified nucleosomes via RING1B but H2Aub1-modified nucleosomes via RYBP. RYBP interactions with both ubiquitin and the nucleosome acidic patch create the high binding affinity that favors RYBP- over RING1B-directed PRC1 binding to H2Aub1-modified nucleosomes; this enables RING1B to monoubiquitinate H2A in neighboring unmodified nucleosomes.
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Affiliation(s)
- Maria Ciapponi
- Laboratory of Chromatin Biology, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Elena Karlukova
- Laboratory of Chromatin Biology, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Sven Schkölziger
- Laboratory of Chromatin Biology, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Christian Benda
- Department of Structural Cell Biology, Max-Planck Institute of Biochemistry, Martinsried, Germany.
| | - Jürg Müller
- Laboratory of Chromatin Biology, Max-Planck Institute of Biochemistry, Martinsried, Germany.
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5
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Ames A, Seman M, Larkin A, Raiymbek G, Chen Z, Levashkevich A, Kim B, Biteen JS, Ragunathan K. Epigenetic memory is governed by an effector recruitment specificity toggle in Heterochromatin Protein 1. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.28.569027. [PMID: 38077059 PMCID: PMC10705379 DOI: 10.1101/2023.11.28.569027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
HP1 proteins are essential for establishing and maintaining transcriptionally silent heterochromatin. They dimerize, forming a binding interface to recruit diverse chromatin-associated factors. HP1 proteins are specialized and rapidly evolve, but the extent of variation required to achieve functional specialization is unknown. To investigate how changes in amino acid sequence impacts epigenetic inheritance, we performed a targeted mutagenesis screen of the S. pombe HP1 homolog, Swi6. Substitutions within an auxiliary surface adjacent to the HP1 dimerization interface produced Swi6 variants with divergent maintenance properties. Remarkably, substitutions at a single amino acid position led to the persistent gain or loss of epigenetic inheritance. These substitutions increased Swi6 chromatin occupancy in vivo and altered Swi6-protein interactions that reprogram H3K9me maintenance. We show that relatively minor changes in Swi6 amino acid composition can lead to profound changes in epigenetic inheritance which provides a redundant mechanism to evolve novel effector specificity. .
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6
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Vogl C, Karapetiants M, Yıldırım B, Kjartansdóttir H, Kosiol C, Bergman J, Majka M, Mikula LC. Inference of genomic landscapes using ordered Hidden Markov Models with emission densities (oHMMed). BMC Bioinformatics 2024; 25:151. [PMID: 38627634 PMCID: PMC11021005 DOI: 10.1186/s12859-024-05751-4] [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: 09/15/2023] [Accepted: 03/18/2024] [Indexed: 04/19/2024] Open
Abstract
BACKGROUND Genomes are inherently inhomogeneous, with features such as base composition, recombination, gene density, and gene expression varying along chromosomes. Evolutionary, biological, and biomedical analyses aim to quantify this variation, account for it during inference procedures, and ultimately determine the causal processes behind it. Since sequential observations along chromosomes are not independent, it is unsurprising that autocorrelation patterns have been observed e.g., in human base composition. In this article, we develop a class of Hidden Markov Models (HMMs) called oHMMed (ordered HMM with emission densities, the corresponding R package of the same name is available on CRAN): They identify the number of comparably homogeneous regions within autocorrelated observed sequences. These are modelled as discrete hidden states; the observed data points are realisations of continuous probability distributions with state-specific means that enable ordering of these distributions. The observed sequence is labelled according to the hidden states, permitting only neighbouring states that are also neighbours within the ordering of their associated distributions. The parameters that characterise these state-specific distributions are inferred. RESULTS We apply our oHMMed algorithms to the proportion of G and C bases (modelled as a mixture of normal distributions) and the number of genes (modelled as a mixture of poisson-gamma distributions) in windows along the human, mouse, and fruit fly genomes. This results in a partitioning of the genomes into regions by statistically distinguishable averages of these features, and in a characterisation of their continuous patterns of variation. In regard to the genomic G and C proportion, this latter result distinguishes oHMMed from segmentation algorithms based in isochore or compositional domain theory. We further use oHMMed to conduct a detailed analysis of variation of chromatin accessibility (ATAC-seq) and epigenetic markers H3K27ac and H3K27me3 (modelled as a mixture of poisson-gamma distributions) along the human chromosome 1 and their correlations. CONCLUSIONS Our algorithms provide a biologically assumption free approach to characterising genomic landscapes shaped by continuous, autocorrelated patterns of variation. Despite this, the resulting genome segmentation enables extraction of compositionally distinct regions for further downstream analyses.
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Affiliation(s)
- Claus Vogl
- Department of Biomedical Sciences and Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, Vienna, Austria.
- Vienna Graduate School of Population Genetics, Vienna, Austria.
| | - Mariia Karapetiants
- Department of Biomedical Sciences and Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, Vienna, Austria
| | - Burçin Yıldırım
- Department of Biomedical Sciences and Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, Vienna, Austria
- Vienna Graduate School of Population Genetics, Vienna, Austria
- Department of Ecology and Genetics, Plant Ecology and Evolution, Uppsala University, Uppsala, Sweden
| | - Hrönn Kjartansdóttir
- Department of Biomedical Sciences and Pathobiology, Vetmeduni Vienna, Veterinärplatz 1, Vienna, Austria
| | - Carolin Kosiol
- Centre for Biological Diversity, School of Biology, University of St Andrews, St Andrews, Scotland, UK
| | - Juraj Bergman
- Department of Biology, Centre for Biodiversity Dynamics in a Changing World (BIOCHANGE) & Section for Ecoinformatics and Biodiversity, Aarhus University, Aarhus, Denmark
| | | | - Lynette Caitlin Mikula
- Centre for Biological Diversity, School of Biology, University of St Andrews, St Andrews, Scotland, UK.
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7
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Tang G, Xia H, Huang Y, Guo Y, Chen Y, Ma Z, Liu W. Liquid-liquid phase separation of H3K27me3 reader BP1 regulates transcriptional repression. Genome Biol 2024; 25:67. [PMID: 38468348 PMCID: PMC10926671 DOI: 10.1186/s13059-024-03209-7] [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: 08/04/2023] [Accepted: 03/04/2024] [Indexed: 03/13/2024] Open
Abstract
BACKGROUND Bromo-adjacent homology-plant homeodomain domain containing protein 1 (BP1) is a reader of histone post-translational modifications in fungi. BP1 recognizes trimethylation of lysine 27 in histone H3 (H3K27me3), an epigenetic hallmark of gene silencing. However, whether and how BP1 participates in transcriptional repression remains poorly understood. RESULTS We report that BP1 forms phase-separated liquid condensates to modulate its biological function in Fusarium graminearum. Deletion assays reveal that intrinsically disordered region 2 (IDR2) of BP1 mediates its liquid-liquid phase separation. The phase separation of BP1 is indispensable for its interaction with suppressor of Zeste 12, a component of polycomb repressive complex 2. Furthermore, IDR2 deletion abolishes BP1-H3K27me3 binding and alleviates the transcriptional repression of secondary metabolism-related genes, especially deoxynivalenol mycotoxin biosynthesis genes. CONCLUSIONS BP1 maintains transcriptional repression by forming liquid-liquid phase-separated condensates, expanding our understanding of the relationship between post-translational modifications and liquid-liquid phase separation.
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Affiliation(s)
- Guangfei Tang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Haoxue Xia
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Yufei Huang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
- College of Plant Protection, Shenyang Agricultural University, Shenyang, 110866, China
| | - Yuanwen Guo
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Yun Chen
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China
| | - Zhonghua Ma
- State Key Laboratory of Rice Biology, Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China
| | - Wende Liu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
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8
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Pelayo MA, Yamaguchi N. Old school, new rules: floral meristem development revealed by 3D gene expression atlases and high-resolution transcription factor-chromatin dynamics. FRONTIERS IN PLANT SCIENCE 2023; 14:1323507. [PMID: 38155851 PMCID: PMC10753784 DOI: 10.3389/fpls.2023.1323507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 11/23/2023] [Indexed: 12/30/2023]
Abstract
The intricate morphology of the flower is primarily established within floral meristems in which floral organs will be defined and from where the developing flower will emerge. Floral meristem development involves multiscale-level regulation, including lineage and positional mechanisms for establishing cell-type identity, and transcriptional regulation mediated by changes in the chromatin environment. However, many key aspects of floral meristem development remain to be determined, such as: 1) the exact role of cellular location in connecting transcriptional inputs to morphological outcomes, and 2) the precise interactions between transcription factors and chromatin regulators underlying the transcriptional networks that regulate the transition from cell proliferation to differentiation during floral meristem development. Here, we highlight recent studies addressing these points through newly developed spatial reconstruction techniques and high-resolution transcription factor-chromatin environment interactions in the model plant Arabidopsis thaliana. Specifically, we feature studies that reconstructed 3D gene expression atlases of the floral meristem. We also discuss how the precise timing of floral meristem specification, floral organ patterning, and floral meristem termination is determined through temporally defined epigenetic dynamics for fine-tuning of gene expression. These studies offer fresh insights into the well-established principles of floral meristem development and outline the potential for further advances in this field in an age of integrated, powerful, multiscale resolution approaches.
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Affiliation(s)
| | - Nobutoshi Yamaguchi
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, Japan
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9
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Yu Y, Wang S, Wang Z, Gao R, Lee J. Arabidopsis thaliana: a powerful model organism to explore histone modifications and their upstream regulations. Epigenetics 2023; 18:2211362. [PMID: 37196184 DOI: 10.1080/15592294.2023.2211362] [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: 11/24/2022] [Revised: 04/07/2023] [Accepted: 04/28/2023] [Indexed: 05/19/2023] Open
Abstract
Histones are subjected to extensive covalent modifications that affect inter-nucleosomal interactions as well as alter chromatin structure and DNA accessibility. Through switching the corresponding histone modifications, the level of transcription and diverse downstream biological processes can be regulated. Although animal systems are widely used in studying histone modifications, the signalling processes that occur outside the nucleus prior to histone modifications have not been well understood due to the limitations including non viable mutants, partial lethality, and infertility of survivors. Here, we review the benefits of using Arabidopsis thaliana as the model organism to study histone modifications and their upstream regulations. Similarities among histones and key histone modifiers such as the Polycomb group (PcG) and Trithorax group (TrxG) in Drosophila, Human, and Arabidopsis are examined. Furthermore, prolonged cold-induced vernalization system has been well-studied and revealed the relationship between the controllable environment input (duration of vernalization), its chromatin modifications of FLOWERING LOCUS C (FLC), following gene expression, and the corresponding phenotypes. Such evidence suggests that research on Arabidopsis can bring insights into incomplete signalling pathways outside of the histone box, which can be achieved through viable reverse genetic screenings based on the phenotypes instead of direct monitoring of histone modifications among individual mutants. The potential upstream regulators in Arabidopsis can provide cues or directions for animal research based on the similarities between them.
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Affiliation(s)
- Yang Yu
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Sihan Wang
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Ziqin Wang
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Renwei Gao
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Joohyun Lee
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
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10
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Sauer PV, Pavlenko E, Cookis T, Zirden LC, Renn J, Singhal A, Hunold P, Hoehne MN, van Ray O, Hänsel-Hertsch R, Sanbonmatsu KY, Nogales E, Poepsel S. Activation of automethylated PRC2 by dimerization on chromatin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.12.562141. [PMID: 37873121 PMCID: PMC10592840 DOI: 10.1101/2023.10.12.562141] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Polycomb Repressive Complex 2 (PRC2) is an epigenetic regulator that trimethylates lysine 27 of histone 3 (H3K27me3) and is essential for embryonic development and cellular differentiation. H3K27me3 is associated with transcriptionally repressed chromatin and is established when PRC2 is allosterically activated upon methyl-lysine binding by the regulatory subunit EED. Automethylation of the catalytic subunit EZH2 stimulates its activity by an unknown mechanism. Here, we show that PRC2 forms a dimer on chromatin in which an inactive, automethylated PRC2 protomer is the allosteric activator of a second PRC2 that is poised to methylate H3 of a substrate nucleosome. Functional assays support our model of allosteric trans-autoactivation via EED, suggesting a novel mechanism mediating context-dependent activation of PRC2. Our work showcases the molecular mechanism of auto-modification coupled dimerization in the regulation of chromatin modifying complexes.
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Affiliation(s)
- Paul V. Sauer
- California Institute for Quantitative Biology (QB3), University of California, Berkeley, California 94720, USA
- Howard Hughes Medical Institute, University of California, Berkeley, California 94720, USA
| | - Egor Pavlenko
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
| | - Trinity Cookis
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
| | - Linda C. Zirden
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
| | - Juliane Renn
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
| | - Ankush Singhal
- Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory
| | - Pascal Hunold
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
- Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931, Cologne, Germany
| | - Michaela N. Hoehne
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
- Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931, Cologne, Germany
| | - Olivia van Ray
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
- Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931, Cologne, Germany
| | - Robert Hänsel-Hertsch
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
- Department of Translational Genomics, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931, Cologne, Germany
- Institute of Human Genetics, University Hospital Cologne, 50931 Cologne, Germany
- Cologne Excellence Cluster for Cellular Stress Responses in Ageing-Associated Diseases (CECAD), University of Cologne, Germany
| | - Karissa Y. Sanbonmatsu
- Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory
| | - Eva Nogales
- California Institute for Quantitative Biology (QB3), University of California, Berkeley, California 94720, USA
- Howard Hughes Medical Institute, University of California, Berkeley, California 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
- Molecular Biophysics and Integrative Bio-Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Simon Poepsel
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Germany
- Cologne Excellence Cluster for Cellular Stress Responses in Ageing-Associated Diseases (CECAD), University of Cologne, Germany
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11
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Salzler HR, Vandadi V, McMichael BD, Brown JC, Boerma SA, Leatham-Jensen MP, Adams KM, Meers MP, Simon JM, Duronio RJ, McKay DJ, Matera AG. Distinct roles for canonical and variant histone H3 lysine-36 in Polycomb silencing. SCIENCE ADVANCES 2023; 9:eadf2451. [PMID: 36857457 PMCID: PMC9977188 DOI: 10.1126/sciadv.adf2451] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 01/31/2023] [Indexed: 05/26/2023]
Abstract
Polycomb complexes regulate cell type-specific gene expression programs through heritable silencing of target genes. Trimethylation of histone H3 lysine 27 (H3K27me3) is essential for this process. Perturbation of H3K36 is thought to interfere with H3K27me3. We show that mutants of Drosophila replication-dependent (H3.2K36R) or replication-independent (H3.3K36R) histone H3 genes generally maintain Polycomb silencing and reach later stages of development. In contrast, combined (H3.3K36RH3.2K36R) mutants display widespread Hox gene misexpression and fail to develop past the first larval stage. Chromatin profiling revealed that the H3.2K36R mutation disrupts H3K27me3 levels broadly throughout silenced domains, whereas these regions are mostly unaffected in H3.3K36R animals. Analysis of H3.3 distributions showed that this histone is enriched at presumptive Polycomb response elements located outside of silenced domains but relatively depleted from those inside. We conclude that H3.2 and H3.3 K36 residues collaborate to repress Hox genes using different mechanisms.
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Affiliation(s)
- Harmony R. Salzler
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | - Vasudha Vandadi
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | - Benjamin D. McMichael
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - John C. Brown
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | - Sally A. Boerma
- Department of Biology, Carleton College, Northfield, MN, USA
| | - Mary P. Leatham-Jensen
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | - Kirsten M. Adams
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Michael P. Meers
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Jeremy M. Simon
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
| | - Robert J. Duronio
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, USA
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
| | - Daniel J. McKay
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, USA
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
| | - A. Gregory Matera
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, USA
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
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12
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Borges BDN. Epigenetic alterations in canine mammary cancer. Genet Mol Biol 2022; 45:e20220131. [PMID: 36279498 PMCID: PMC9593226 DOI: 10.1590/1678-4685-gmb-2022-0131] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 09/09/2022] [Indexed: 11/04/2022] Open
Abstract
In dogs, mammary cancer is the most common tumor type, especially in unspayed females. As in humans, this type of cancer has spontaneous development and is influenced by several risk factors, such as age and hormonal exposure in addition to genetic and epigenetic factors. Epigenetic mechanisms are responsible for gene expression modulation without alterations in the DNA sequence and include but are not limited to DNA methylation, histone modifications, and noncoding RNAs. Epigenetic patterns are known to influence a variety of biological mechanisms, such as cellular differentiation and development, and dysregulations of those patterns may result in several diseases, such as cancer. In this respect, this review summarizes the main findings concerning epigenetic alterations in canine mammary cancer, their relationship with the carcinogenic process, and their use as diagnostic and prognostic markers.
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Affiliation(s)
- Bárbara do Nascimento Borges
- Universidade Federal do Pará, Instituto de Ciências Biológicas Laboratório de Biologia Molecular, Belém, PA, Brazil
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13
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Epigenetic factor competition reshapes the EMT landscape. Proc Natl Acad Sci U S A 2022; 119:e2210844119. [PMID: 36215492 PMCID: PMC9586264 DOI: 10.1073/pnas.2210844119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The emergence of and transitions between distinct phenotypes in isogenic cells can be attributed to the intricate interplay of epigenetic marks, external signals, and gene-regulatory elements. These elements include chromatin remodelers, histone modifiers, transcription factors, and regulatory RNAs. Mathematical models known as gene-regulatory networks (GRNs) are an increasingly important tool to unravel the workings of such complex networks. In such models, epigenetic factors are usually proposed to act on the chromatin regions directly involved in the expression of relevant genes. However, it has been well-established that these factors operate globally and compete with each other for targets genome-wide. Therefore, a perturbation of the activity of a regulator can redistribute epigenetic marks across the genome and modulate the levels of competing regulators. In this paper, we propose a conceptual and mathematical modeling framework that incorporates both local and global competition effects between antagonistic epigenetic regulators, in addition to local transcription factors, and show the counterintuitive consequences of such interactions. We apply our approach to recent experimental findings on the epithelial-mesenchymal transition (EMT). We show that it can explain the puzzling experimental data, as well as provide verifiable predictions.
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14
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Pavlenko E, Ruengeler T, Engel P, Poepsel S. Functions and Interactions of Mammalian KDM5 Demethylases. Front Genet 2022; 13:906662. [PMID: 35899196 PMCID: PMC9309374 DOI: 10.3389/fgene.2022.906662] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 06/06/2022] [Indexed: 12/26/2022] Open
Abstract
Mammalian histone demethylases of the KDM5 family are mediators of gene expression dynamics during developmental, cellular differentiation, and other nuclear processes. They belong to the large group of JmjC domain containing, 2-oxoglutarate (2-OG) dependent oxygenases and target methylated lysine 4 of histone H3 (H3K4me1/2/3), an epigenetic mark associated with active transcription. In recent years, KDM5 demethylases have gained increasing attention due to their misregulation in many cancer entities and are intensively explored as therapeutic targets. Despite these implications, the molecular basis of KDM5 function has so far remained only poorly understood. Little is known about mechanisms of nucleosome recognition, the recruitment to genomic targets, as well as the local regulation of demethylase activity. Experimental evidence suggests close physical and functional interactions with epigenetic regulators such as histone deacetylase (HDAC) containing complexes, as well as the retinoblastoma protein (RB). To understand the regulation of KDM5 proteins in the context of chromatin, these interactions have to be taken into account. Here, we review the current state of knowledge on KDM5 function, with a particular emphasis on molecular interactions and their potential implications. We will discuss and outline open questions that need to be addressed to better understand histone demethylation and potential demethylation-independent functions of KDM5s. Addressing these questions will increase our understanding of histone demethylation and allow us to develop strategies to target individual KDM5 enzymes in specific biological and disease contexts.
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Affiliation(s)
- Egor Pavlenko
- University of Cologne, Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, Cologne, Germany
| | - Till Ruengeler
- University of Cologne, Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, Cologne, Germany
| | - Paulina Engel
- University of Cologne, Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, Cologne, Germany
| | - Simon Poepsel
- University of Cologne, Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, Cologne, Germany
- Cologne Excellence Cluster for Cellular Stress Responses in Ageing-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- *Correspondence: Simon Poepsel,
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15
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Lensch S, Herschl MH, Ludwig CH, Sinha J, Hinks MM, Mukund A, Fujimori T, Bintu L. Dynamic spreading of chromatin-mediated gene silencing and reactivation between neighboring genes in single cells. eLife 2022; 11:e75115. [PMID: 35678392 PMCID: PMC9183234 DOI: 10.7554/elife.75115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 03/23/2022] [Indexed: 12/02/2022] Open
Abstract
In mammalian cells genes that are in close proximity can be transcriptionally coupled: silencing or activating one gene can affect its neighbors. Understanding these dynamics is important for natural processes, such as heterochromatin spreading during development and aging, and when designing synthetic gene regulation circuits. Here, we systematically dissect this process in single cells by recruiting and releasing repressive chromatin regulators at dual-gene synthetic reporters, and measuring how fast gene silencing and reactivation spread as a function of intergenic distance and configuration of insulator elements. We find that silencing by KRAB, associated with histone methylation, spreads between two genes within hours, with a time delay that increases with distance. This fast KRAB-mediated spreading is not blocked by the classical cHS4 insulators. Silencing by histone deacetylase HDAC4 of the upstream gene can also facilitate background silencing of the downstream gene by PRC2, but with a days-long delay that does not change with distance. This slower silencing can sometimes be stopped by insulators. Gene reactivation of neighboring genes is also coupled, with strong promoters and insulators determining the order of reactivation. Our data can be described by a model of multi-gene regulation that builds upon previous knowledge of heterochromatin spreading, where both gene silencing and gene reactivation can act at a distance, allowing for coordinated dynamics via chromatin regulator recruitment.
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Affiliation(s)
- Sarah Lensch
- Department of Bioengineering, Stanford UniversityStanfordUnited States
| | - Michael H Herschl
- University of California, Berkeley—University of California, San Francisco Graduate Program in BioengineeringBerkeleyUnited States
| | - Connor H Ludwig
- Department of Bioengineering, Stanford UniversityStanfordUnited States
| | - Joydeb Sinha
- Department of Chemical and Systems Biology, Stanford UniversityStanfordUnited States
| | - Michaela M Hinks
- Department of Bioengineering, Stanford UniversityStanfordUnited States
| | - Adi Mukund
- Biophysics Program, Stanford UniversityStanfordUnited States
| | - Taihei Fujimori
- Department of Bioengineering, Stanford UniversityStanfordUnited States
| | - Lacramioara Bintu
- Department of Bioengineering, Stanford UniversityStanfordUnited States
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16
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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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17
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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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