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Godneeva B, Fejes Tóth K, Quan B, Chou TF, Aravin AA. Impact of Germline Depletion of Bonus on Chromatin State in Drosophila Ovaries. Cells 2023; 12:2629. [PMID: 37998364 PMCID: PMC10670193 DOI: 10.3390/cells12222629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 11/07/2023] [Accepted: 11/13/2023] [Indexed: 11/25/2023] Open
Abstract
Gene expression is controlled via complex regulatory mechanisms involving transcription factors, chromatin modifications, and chromatin regulatory factors. Histone modifications, such as H3K27me3, H3K9ac, and H3K27ac, play an important role in controlling chromatin accessibility and transcriptional output. In vertebrates, the Transcriptional Intermediary Factor 1 (TIF1) family of proteins play essential roles in transcription, cell differentiation, DNA repair, and mitosis. Our study focused on Bonus, the sole member of the TIF1 family in Drosophila, to investigate its role in organizing epigenetic modifications. Our findings demonstrated that depleting Bonus in ovaries leads to a mild reduction in the H3K27me3 level over transposon regions and alters the distribution of active H3K9ac marks on specific protein-coding genes. Additionally, through mass spectrometry analysis, we identified novel interacting partners of Bonus in ovaries, such as PolQ, providing a comprehensive understanding of the associated molecular pathways. Furthermore, our research revealed Bonus's interactions with the Polycomb Repressive Complex 2 and its co-purification with select histone acetyltransferases, shedding light on the underlying mechanisms behind these changes in chromatin modifications.
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Affiliation(s)
- Baira Godneeva
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Katalin Fejes Tóth
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Baiyi Quan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Proteome Exploration Laboratory, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Tsui-Fen Chou
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Proteome Exploration Laboratory, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Alexei A. Aravin
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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2
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Franco-Echevarría E, Nielsen M, Schulten A, Cheema J, Morgan TE, Bienz M, Dean C. Distinct accessory roles of Arabidopsis VEL proteins in Polycomb silencing. Genes Dev 2023; 37:801-817. [PMID: 37734835 PMCID: PMC7615239 DOI: 10.1101/gad.350814.123] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 08/31/2023] [Indexed: 09/23/2023]
Abstract
Polycomb repressive complex 2 (PRC2) mediates epigenetic silencing of target genes in animals and plants. In Arabidopsis, PRC2 is required for the cold-induced epigenetic silencing of the FLC floral repressor locus to align flowering with spring. During this process, PRC2 relies on VEL accessory factors, including the constitutively expressed VRN5 and the cold-induced VIN3. The VEL proteins are physically associated with PRC2, but their individual functions remain unclear. Here, we show an intimate association between recombinant VRN5 and multiple components within a reconstituted PRC2, dependent on a compact conformation of VRN5 central domains. Key residues mediating this compact conformation are conserved among VRN5 orthologs across the plant kingdom. In contrast, VIN3 interacts with VAL1, a transcriptional repressor that binds directly to FLC These associations differentially affect their role in H3K27me deposition: Both proteins are required for H3K27me3, but only VRN5 is necessary for H3K27me2. Although originally defined as vernalization regulators, VIN3 and VRN5 coassociate with many targets in the Arabidopsis genome that are modified with H3K27me3. Our work therefore reveals the distinct accessory roles for VEL proteins in conferring cold-induced silencing on FLC, with broad relevance for PRC2 targets generally.
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Affiliation(s)
- Elsa Franco-Echevarría
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Mathias Nielsen
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Anna Schulten
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Jitender Cheema
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Tomos E Morgan
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Mariann Bienz
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom;
| | - Caroline Dean
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom;
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
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3
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Zhu T, Hu J, Yang X, Kong L, Ling J, Wang J, An S. Analysis of polycomb repressive complex 2 (PRC2) subunits in Picea abies with a focus on embryo development. BMC PLANT BIOLOGY 2023; 23:347. [PMID: 37391710 DOI: 10.1186/s12870-023-04359-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 06/22/2023] [Indexed: 07/02/2023]
Abstract
BACKGROUND Conserved polycomb repressive complex 2 (PRC2) mediates H3K27me3 to direct transcriptional repression and has a key role in cell fate determination and cell differentiation in both animals and plants. PRC2 subunits have undergone independent multiplication and functional divergence in higher plants. However, relevant information is still absent in gymnosperms. RESULTS To launch gymnosperm PRC2 research, we identified and cloned the PRC2 core component genes in the conifer model species Picea abies, including one Esc/FIE homolog PaFIE, two p55/MSI homologs PaMSI1a and PaMSI1b, two E(z) homologs PaKMT6A2 and PaKMT6A4, a Su(z)12 homolog PaEMF2 and a PaEMF2-like fragment. Phylogenetic and protein domain analyses were conducted. The Esc/FIE homologs were highly conserved in the land plant, except the monocots. The other gymnospermous PRC2 subunits underwent independent evolution with angiospermous species to different extents. The relative transcript levels of these genes were measured in endosperm and zygotic and somatic embryos at different developmental stages. The obtained results proposed the involvement of PaMSI1b and PaKMT6A4 in embryogenesis and PaKMT6A2 and PaEMF2 in the transition from embryos to seedlings. The PaEMF2-like fragment was predominantly expressed in the endosperm but not in the embryo. In addition, immunohistochemistry assay showed that H3K27me3 deposits were generally enriched at meristem regions during seed development in P. abies. CONCLUSIONS This study reports the first characterization of the PRC2 core component genes in the coniferous species P. abies. Our work may enable a deeper understanding of the cell reprogramming process during seed and embryo development and may guide further research on embryonic potential and development in conifers.
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Affiliation(s)
- Tianqing Zhu
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Haidian District, Dongxiaofu 1, Beijing, 100091, People's Republic of China
| | - Jiwen Hu
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of State Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, PR China
| | - Xiaowei Yang
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of State Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, PR China
| | - Lisheng Kong
- Department of Biology, Centre for Forest Biology, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Juanjuan Ling
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of State Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, PR China
| | - Junhui Wang
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Haidian District, Dongxiaofu 1, Beijing, 100091, People's Republic of China.
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of State Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, PR China.
| | - Sanping An
- Xiaolongshan Forestry Protection Center of Gansu Province, Tianshui, 741020, Gansu, PR China
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4
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Cabrita B, Martinho RG. Genetic and Epigenetic Regulation of Drosophila Oocyte Determination. J Dev Biol 2023; 11:21. [PMID: 37367475 DOI: 10.3390/jdb11020021] [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: 04/28/2023] [Revised: 05/18/2023] [Accepted: 05/20/2023] [Indexed: 06/28/2023] Open
Abstract
Primary oocyte determination occurs in many organisms within a germ line cyst, a multicellular structure composed of interconnected germ cells. However, the structure of the cyst is itself highly diverse, which raises intriguing questions about the benefits of this stereotypical multicellular environment for female gametogenesis. Drosophila melanogaster is a well-studied model for female gametogenesis, and numerous genes and pathways critical for the determination and differentiation of a viable female gamete have been identified. This review provides an up-to-date overview of Drosophila oocyte determination, with a particular emphasis on the mechanisms that regulate germ line gene expression.
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Affiliation(s)
- Brigite Cabrita
- Department of Medical Sciences, Institute of Biomedicine (iBiMED), University of Aveiro, Agra do Crasto, Edifício 30, 3810-193 Aveiro, Portugal
| | - Rui Gonçalo Martinho
- Department of Medical Sciences, Institute of Biomedicine (iBiMED), University of Aveiro, Agra do Crasto, Edifício 30, 3810-193 Aveiro, Portugal
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Shirahama Y, Yamamoto K. The E2F6 Transcription Factor is Associated with the Mammalian SUZ12-Containing Polycomb Complex. Kurume Med J 2023; 67:171-183. [PMID: 36464274 DOI: 10.2739/kurumemedj.ms674006] [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: 12/05/2022]
Abstract
The Polycomb group protein (PcG) SUZ12 forms Polycomb repressive complexes together with histone methyltransferase EZH2. Although the complexes have been demonstrated to be involved in epigenetic maintenance of gene expression in a transcriptional repressive state, it is unclear how they are recruited to the target genes. Here we report that SUZ12 directly interacts with site-specific transcriptional repressor E2F6 and forms a complex together with EZH2. SUZ12 interacts with E2F6 selectively among the E2F family proteins and E2F6- containing SUZ12-EZH2 complex was biochemically purified from HEK293 cells stably expressing Flag-tagged SUZ12. Chromatin immunoprecipitation assays revealed the target genes of the E2F6-SUZ12-EZH2 complex. Contrary to expectation, the promoter regions of these genes are not or only weakly tri-methylated at histone H3-K27, and their expression is down-regulated by depletion of EZH2. Given that the transactivation function of SUZ12-EZH2 has been previously reported, the inhibitory effect on E2F6-mediated transcriptional repression by physical interaction can be considered a candidate mechanism of gene activation by these PcGs.
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Affiliation(s)
- Yuko Shirahama
- Department of Medical Biochemistry, Kurume University School of Medicine
| | - Ken Yamamoto
- Department of Medical Biochemistry, Kurume University School of Medicine
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Hajirnis N, Pandey S, Mishra RK. CRISPR/Cas9 and FLP-FRT mediated regulatory dissection of the BX-C of Drosophila melanogaster. CHROMOSOME RESEARCH : AN INTERNATIONAL JOURNAL ON THE MOLECULAR, SUPRAMOLECULAR AND EVOLUTIONARY ASPECTS OF CHROMOSOME BIOLOGY 2023; 31:7. [PMID: 36719476 DOI: 10.1007/s10577-023-09716-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/23/2022] [Accepted: 11/28/2022] [Indexed: 02/01/2023]
Abstract
The homeotic genes or Hox define the anterior-posterior (AP) body axis formation in bilaterians and are often present on the chromosome in an order collinear to their function across the AP axis. However, there are many cases wherein the Hox are not collinear, but their expression pattern is conserved across the AP axis. The expression pattern of Hox is attributed to the cis-regulatory modules (CRMs) consisting of enhancers, initiators, or repressor elements that regulate the genes in a segment-specific manner. In the Drosophila melanogaster Hox complex, the bithorax complex (BX-C) and even the CRMs are organized in an order that is collinear to their function in the thoracic and abdominal segments. In the present study, the regulatorily inert regions were targeted using CRISPR/Cas9 to generate a series of transgenic lines with the insertion of FRT sequences. These FRT lines are repurposed to shuffle the CRMs associated with Abd-B to generate modular deletion, duplication, or inversion of multiple CRMs. The rearrangements yielded entirely novel phenotypes in the fly suggesting the requirement of such complex manipulations to address the significance of higher order arrangement of the CRMs. The functional map and the transgenic flies generated in this study are important resources to decipher the collective ability of multiple regulatory elements in the eukaryotic genome to function as complex modules.
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Affiliation(s)
- Nikhil Hajirnis
- CSIR - Centre for Cellular and Molecular Biology, Hyderabad, India.,Department of Anatomy and Neurobiology, University of Maryland, Baltimore, USA
| | | | - Rakesh K Mishra
- CSIR - Centre for Cellular and Molecular Biology, Hyderabad, India. .,AcSIR - Academy of Scientific and Innovative Research, Ghaziabad, India. .,Tata Institute for Genetics and Society (TIGS), Bangalore, India.
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7
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Feijão T, Marques B, Silva RD, Carvalho C, Sobral D, Matos R, Tan T, Pereira A, Morais-de-Sá E, Maiato H, DeLuca SZ, Martinho RG. Polycomb group (PcG) proteins prevent the assembly of abnormal synaptonemal complex structures during meiosis. Proc Natl Acad Sci U S A 2022; 119:e2204701119. [PMID: 36215502 PMCID: PMC9586294 DOI: 10.1073/pnas.2204701119] [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: 03/16/2022] [Accepted: 07/18/2022] [Indexed: 11/18/2022] Open
Abstract
The synaptonemal complex (SC) is a proteinaceous scaffold that is assembled between paired homologous chromosomes during the onset of meiosis. Timely expression of SC coding genes is essential for SC assembly and successful meiosis. However, SC components have an intrinsic tendency to self-organize into abnormal repetitive structures, which are not assembled between the paired homologs and whose formation is potentially deleterious for meiosis and gametogenesis. This creates an interesting conundrum, where SC genes need to be robustly expressed during meiosis, but their expression must be carefully regulated to prevent the formation of anomalous SC structures. In this manuscript, we show that the Polycomb group protein Sfmbt, the Drosophila ortholog of human MBTD1 and L3MBTL2, is required to avoid excessive expression of SC genes during prophase I. Although SC assembly is normal after Sfmbt depletion, SC disassembly is abnormal with the formation of multiple synaptonemal complexes (polycomplexes) within the oocyte. Overexpression of the SC gene corona and depletion of other Polycomb group proteins are similarly associated with polycomplex formation during SC disassembly. These polycomplexes are highly dynamic and have a well-defined periodic structure. Further confirming the importance of Sfmbt, germ line depletion of this protein is associated with significant metaphase I defects and a reduction in female fertility. Since transcription of SC genes mostly occurs during early prophase I, our results suggest a role of Sfmbt and other Polycomb group proteins in downregulating the expression of these and other early prophase I genes during later stages of meiosis.
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Affiliation(s)
- Tália Feijão
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139 Faro, Portugal
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, 4200-135 Portugal
- Department of Medical Sciences and Institute for Biomedicine, Universidade de Aveiro, 3810-193 Aveiro, Portugal
| | - Bruno Marques
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139 Faro, Portugal
| | - Rui D. Silva
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139 Faro, Portugal
- Faculty of Medicine and Biomedical Sciences, Universidade do Algarve, 8005-139 Faro, Portugal
| | - Célia Carvalho
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Daniel Sobral
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, School of Science and Technology, NOVA University Lisbon, 2819-516 Caparica, Portugal
- Applied Molecular Biosciences Unit (UCIBIO), Department of Life Sciences, School of Science and Technology, NOVA University Lisbon, Caparica, 2819-516 Portugal
| | - Ricardo Matos
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139 Faro, Portugal
| | - Tian Tan
- Department of Biology, Brandeis University, Waltham, MA 02453
| | - António Pereira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, 4200-135 Portugal
| | - Eurico Morais-de-Sá
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, 4200-135 Portugal
| | - Hélder Maiato
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, 4200-135 Portugal
| | | | - Rui Gonçalo Martinho
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139 Faro, Portugal
- Department of Medical Sciences and Institute for Biomedicine, Universidade de Aveiro, 3810-193 Aveiro, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
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8
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Snel B, van den Heuvel S, Seidl MF. Caenorhabditis elegans MES-3 is a highly divergent ortholog of the canonical PRC2 component SUZ12. iScience 2022; 25:104633. [PMID: 35800781 PMCID: PMC9253717 DOI: 10.1016/j.isci.2022.104633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/27/2022] [Accepted: 06/13/2022] [Indexed: 11/24/2022] Open
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9
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Histone H3K27 methylation-mediated repression of Hairy regulates insect developmental transition by modulating ecdysone biosynthesis. Proc Natl Acad Sci U S A 2021; 118:2101442118. [PMID: 34429358 DOI: 10.1073/pnas.2101442118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Insect development is cooperatively orchestrated by the steroid hormone ecdysone and juvenile hormone (JH). The polycomb repressive complex 2 (PRC2)-mediated histone H3K27 trimethylation (H3K27me3) epigenetically silences gene transcription and is essential for a range of biological processes, but the functions of H3K27 methylation in insect hormone action are poorly understood. Here, we demonstrate that H3K27 methylation-mediated repression of Hairy transcription in the larval prothoracic gland (PG) is required for ecdysone biosynthesis in Bombyx and Drosophila H3K27me3 levels in the PG are dynamically increased during the last larval instar. H3K27me3 reduction induced by the down-regulation of PRC2 activity via inhibitor treatment in Bombyx or PG-specific knockdown of the PRC2 component Su(z)12 in Drosophila diminishes ecdysone biosynthesis and disturbs the larval-pupal transition. Mechanistically, H3K27 methylation targets the JH signal transducer Hairy to repress its transcription in the PG; PG-specific knockdown or overexpression of the Hairy gene disrupts ecdysone biosynthesis and developmental transition; and developmental defects caused by PG-specific Su(z)12 knockdown can be partially rescued by Hairy down-regulation. The application of JH mimic to the PG decreases both H3K27me3 levels and Su(z)12 expression. Altogether, our study reveals that PRC2-mediated H3K27 methylation at Hairy in the PG during the larval period is required for ecdysone biosynthesis and the larval-pupal transition and provides insights into epigenetic regulation of the crosstalk between JH and ecdysone during insect development.
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10
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Li C, Wang C. LG-ESSs and HG-ESSs: underlying molecular alterations and potential therapeutic strategies. J Zhejiang Univ Sci B 2021; 22:633-646. [PMID: 34414699 PMCID: PMC8377580 DOI: 10.1631/jzus.b2000797] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 03/19/2021] [Accepted: 03/19/2021] [Indexed: 12/29/2022]
Abstract
Endometrial stromal tumors (ESTs) include endometrial stromal nodule (ESN), low-grade endometrial stromal sarcoma (LG-ESS), high-grade endometrial stromal sarcoma (HG-ESS), and undifferentiated uterine sarcoma (UUS). Since these are rare tumor types, there is an unmet clinical need for the systematic therapy of advanced LG-ESS or HG-ESS. Cytogenetic and molecular advances in ESTs have shown that multiple recurrent gene fusions are present in a large proportion of LG-ESSs, and HG-ESSs are identified by the tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein epsilon (YWHAE)-family with sequence similarity 22 (FAM22) fusion. Recently, a group of ESSs harboring both zinc finger CCCH domain-containing protein 7B (ZC3H7B)-B-cell lymphoma 6 corepressor(BCOR) fusion and internal tandem duplication (ITD) of the BCOR gene have been provisionally classified as HG-ESSs. In this review, we firstly describe current knowledge about the molecular characteristics of recurrent aberrant proteins and their roles in the tumorigenesis of LG-ESSs and HG-ESSs. Next, we summarize the possibly shared signal pathways in the tumorigenesis of LG-ESSs and HG-ESSs, and list potentially actionable targets. Finally, based on the above discussion, we propose a few promising therapeutic strategies for LG-ESSs and HG-ESSs with recurrent gene alterations.
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Affiliation(s)
- Chunhui Li
- Quality Management Office, The Second Hospital of Jilin University, Changchun 130041, China
| | - Chunhong Wang
- Department of Hematology and Oncology, The Second Hospital of Jilin University, Changchun 130041, China.
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11
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Post-Embryonic Phase Transitions Mediated by Polycomb Repressive Complexes in Plants. Int J Mol Sci 2021; 22:ijms22147533. [PMID: 34299153 PMCID: PMC8305008 DOI: 10.3390/ijms22147533] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/05/2021] [Accepted: 07/09/2021] [Indexed: 12/20/2022] Open
Abstract
Correct timing of developmental phase transitions is critical for the survival and fitness of plants. Developmental phase transitions in plants are partially promoted by controlling relevant genes into active or repressive status. Polycomb Repressive Complex1 (PRC1) and PRC2, originally identified in Drosophila, are essential in initiating and/or maintaining genes in repressive status to mediate developmental phase transitions. Our review summarizes mechanisms in which the embryo-to-seedling transition, the juvenile-to-adult transition, and vegetative-to-reproductive transition in plants are mediated by PRC1 and PRC2, and suggests that PRC1 could act either before or after PRC2, or that they could function independently of each other. Details of the exact components of PRC1 and PRC2 in each developmental phase transitions and how they are recruited or removed will need to be addressed in the future.
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12
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Labandera A, Tedds HM, Bailey M, Sprigg C, Etherington RD, Akintewe O, Kalleechurn G, Holdsworth MJ, Gibbs DJ. The PRT6 N-degron pathway restricts VERNALIZATION 2 to endogenous hypoxic niches to modulate plant development. THE NEW PHYTOLOGIST 2021; 229:126-139. [PMID: 32043277 PMCID: PMC7754370 DOI: 10.1111/nph.16477] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 02/04/2020] [Indexed: 05/20/2023]
Abstract
VERNALIZATION2 (VRN2), an angiosperm-specific subunit of the polycomb repressive complex 2 (PRC2), is an oxygen (O2 )-regulated target of the PCO branch of the PRT6 N-degron pathway of ubiquitin-mediated proteolysis. How this post-translational regulation coordinates VRN2 activity remains to be fully established. Here we use Arabidopsis thaliana ecotypes, mutants and transgenic lines to determine how control of VRN2 stability contributes to its functions during plant development. VRN2 localizes to endogenous hypoxic regions in aerial and root tissues. In the shoot apex, VRN2 differentially modulates flowering time dependent on photoperiod, whilst its presence in lateral root primordia and the root apical meristem negatively regulates root system architecture. Ectopic accumulation of VRN2 does not enhance its effects on flowering, but does potentiate its repressive effects on root growth. In late-flowering vernalization-dependent ecotypes, VRN2 is only active outside meristems when its proteolysis is inhibited in response to cold exposure, as its function requires concomitant cold-triggered increases in other PRC2 subunits and cofactors. We conclude that the O2 -sensitive N-degron of VRN2 has a dual function, confining VRN2 to meristems and primordia, where it has specific developmental roles, whilst also permitting broad accumulation outside of meristems in response to environmental cues, leading to other functions.
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Affiliation(s)
| | - Hannah M. Tedds
- School of BiosciencesUniversity of BirminghamEdgbastonB15 2TTUK
| | - Mark Bailey
- School of BiosciencesUniversity of BirminghamEdgbastonB15 2TTUK
| | - Colleen Sprigg
- School of BiosciencesUniversity of BirminghamEdgbastonB15 2TTUK
| | | | | | | | | | - Daniel J. Gibbs
- School of BiosciencesUniversity of BirminghamEdgbastonB15 2TTUK
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13
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Liu X. A Structural Perspective on Gene Repression by Polycomb Repressive Complex 2. Subcell Biochem 2020; 96:519-562. [PMID: 33252743 DOI: 10.1007/978-3-030-58971-4_17] [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: 03/30/2023]
Abstract
Polycomb Repressive Complex 2 (PRC2) is a major repressive chromatin complex formed by the Polycomb Group (PcG) proteins. PRC2 mediates trimethylation of histone H3 lysine 27 (H3K27me3), a hallmark of gene silencing. PRC2 is a key regulator of development, impacting many fundamental biological processes, like stem cell differentiation in mammals and vernalization in plants. Misregulation of PRC2 function is linked to a variety of human cancers and developmental disorders. In correlation with its diverse roles in development, PRC2 displays a high degree of compositional complexity and plasticity. Structural biology research over the past decade has shed light on the molecular mechanisms of the assembly, catalysis, allosteric activation, autoinhibition, chemical inhibition, dimerization and chromatin targeting of various developmentally regulated PRC2 complexes. In addition to these aspects, structure-function analysis is also discussed in connection with disease data in this chapter.
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Affiliation(s)
- Xin Liu
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, UT Southwestern Medical Center, Dallas, TX, 75390, USA.
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14
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Courtney AJ, Kamei M, Ferraro AR, Gai K, He Q, Honda S, Lewis ZA. Normal Patterns of Histone H3K27 Methylation Require the Histone Variant H2A.Z in Neurospora crassa. Genetics 2020; 216:51-66. [PMID: 32651262 PMCID: PMC7463285 DOI: 10.1534/genetics.120.303442] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 07/05/2020] [Indexed: 12/14/2022] Open
Abstract
Neurospora crassa contains a minimal Polycomb repression system, which provides rich opportunities to explore Polycomb-mediated repression across eukaryotes and enables genetic studies that can be difficult in plant and animal systems. Polycomb Repressive Complex 2 is a multi-subunit complex that deposits mono-, di-, and trimethyl groups on lysine 27 of histone H3, and trimethyl H3K27 is a molecular marker of transcriptionally repressed facultative heterochromatin. In mouse embryonic stem cells and multiple plant species, H2A.Z has been found to be colocalized with H3K27 methylation. H2A.Z is required for normal H3K27 methylation in these experimental systems, though the regulatory mechanisms are not well understood. We report here that Neurospora crassa mutants lacking H2A.Z or SWR-1, the ATP-dependent histone variant exchanger, exhibit a striking reduction in levels of H3K27 methylation. RNA-sequencing revealed downregulation of eed, encoding a subunit of PRC2, in an hH2Az mutant compared to wild type, and overexpression of EED in a ΔhH2Az;Δeed background restored most H3K27 methylation. Reduced eed expression leads to region-specific losses of H3K27 methylation, suggesting that differential dependence on EED concentration is critical for normal H3K27 methylation at certain regions in the genome.
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Affiliation(s)
- Abigail J Courtney
- Department of Microbiology, University of Georgia, Athens, Georgia 30602
| | - Masayuki Kamei
- Department of Microbiology, University of Georgia, Athens, Georgia 30602
| | - Aileen R Ferraro
- Department of Microbiology, University of Georgia, Athens, Georgia 30602
| | - Kexin Gai
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Qun He
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shinji Honda
- Division of Chromosome Biology, Faculty of Medical Sciences, University of Fukui, 910-1193, Japan
| | - Zachary A Lewis
- Department of Microbiology, University of Georgia, Athens, Georgia 30602
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15
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Abstract
The idea that epigenetic determinants such as DNA methylation, histone modifications or RNA can be passed to the next generation through meiotic products (gametes) is long standing. Such meiotic epigenetic inheritance (MEI) is fairly common in yeast, plants and nematodes, but its extent in mammals has been much debated. Advances in genomics techniques are now driving the profiling of germline and zygotic epigenomes, thereby improving our understanding of MEI in diverse species. Whereas the role of DNA methylation in MEI remains unclear, insights from genome-wide studies suggest that a previously underappreciated fraction of mammalian genomes bypass epigenetic reprogramming during development. Notably, intergenerational inheritance of histone modifications, tRNA fragments and microRNAs can affect gene regulation in the offspring. It is important to note that MEI in mammals rarely constitutes transgenerational epigenetic inheritance (TEI), which spans multiple generations. In this Review, we discuss the examples of MEI in mammals, including mammalian epigenome reprogramming, and the molecular mechanisms of MEI in vertebrates in general. We also discuss the implications of the inheritance of histone modifications and small RNA for embryogenesis in metazoans, with a particular focus on insights gained from genome-wide studies.
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16
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Seller CA, Cho CY, O'Farrell PH. Rapid embryonic cell cycles defer the establishment of heterochromatin by Eggless/SetDB1 in Drosophila. Genes Dev 2019; 33:403-417. [PMID: 30808658 PMCID: PMC6446540 DOI: 10.1101/gad.321646.118] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/14/2019] [Indexed: 12/15/2022]
Abstract
Acquisition of chromatin modifications during embryogenesis distinguishes different regions of an initially naïve genome. In many organisms, repetitive DNA is packaged into constitutive heterochromatin that is marked by di/trimethylation of histone H3K9 and the associated protein HP1a. These modifications enforce the unique epigenetic properties of heterochromatin. However, in the early Drosophila melanogaster embryo, the heterochromatin lacks these modifications, which appear only later, when rapid embryonic cell cycles slow down at the midblastula transition (MBT). Here we focus on the initial steps restoring heterochromatic modifications in the embryo. We describe the JabbaTrap, a technique for inactivating maternally provided proteins in embryos. Using the JabbaTrap, we reveal a major requirement for the methyltransferase Eggless/SetDB1 in the establishment of heterochromatin. In contrast, other methyltransferases contribute minimally. Live imaging reveals that endogenous Eggless gradually accumulates on chromatin in interphase but then dissociates in mitosis, and its accumulation must restart in the next cell cycle. Cell cycle slowing as the embryo approaches the MBT permits increasing accumulation and action of Eggless at its targets. Experimental manipulation of interphase duration shows that cell cycle speed regulates Eggless. We propose that developmental slowing of the cell cycle times embryonic heterochromatin formation.
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Affiliation(s)
- Charles A Seller
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Chun-Yi Cho
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Patrick H O'Farrell
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
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17
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MiR-34 inhibits polycomb repressive complex 2 to modulate chaperone expression and promote healthy brain aging. Nat Commun 2018; 9:4188. [PMID: 30305625 PMCID: PMC6180074 DOI: 10.1038/s41467-018-06592-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 09/07/2018] [Indexed: 02/07/2023] Open
Abstract
Aging is a prominent risk factor for neurodegenerative disease. Defining gene expression mechanisms affecting healthy brain aging should lead to insight into genes that modulate susceptibility to disease. To define such mechanisms, we have pursued analysis of miR-34 mutants in Drosophila. The miR-34 mutant brain displays a gene expression profile of accelerated aging, and miR-34 upregulation is a potent suppressor of polyglutamine-induced neurodegeneration. We demonstrate that Pcl and Su(z)12, two components of polycomb repressive complex 2, (PRC2), are targets of miR-34, with implications for age-associated processes. Because PRC2 confers the repressive H3K27me3 mark, we hypothesize that miR-34 modulates PRC2 activity to relieve silencing of genes promoting healthful aging. Gene expression profiling of the brains of hypomorphic mutants in Enhancer of zeste (E(z)), the enzymatic methyltransferase component of PRC2, revealed a younger brain transcriptome profile and identified the small heat shock proteins as key genes reduced in expression with age. miR-34 is known to regulate age-related gene expression in the Drosophila brain, and miR-34 overexpression can attenuate neurodegeneration induced by polyQ-expanded proteins. Here, Kennerdell and colleagues show that miR-34 confers longevity and neuroprotection via an epigenetic regulator Polycomb Repressive Complex 2 and molecular chaperone expression.
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18
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Huminiecki L. Modelling of the breadth of expression from promoter architectures identifies pro-housekeeping transcription factors. PLoS One 2018; 13:e0198961. [PMID: 29928029 PMCID: PMC6013173 DOI: 10.1371/journal.pone.0198961] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 05/28/2018] [Indexed: 12/22/2022] Open
Abstract
Understanding how regulatory elements control mammalian gene expression is a challenge of post-genomic era. We previously reported that size of proximal promoter architecture predicted the breadth of expression (fraction of tissues in which a gene is expressed). Herein, the contributions of individual transcription factors (TFs) were quantified. Several technologies of statistical modelling were utilized and compared: tree models, generalized linear models (GLMs, without and with regularization), Bayesian GLMs and random forest. Both linear and non-linear modelling strategies were explored. Encouragingly, different models led to similar statistical conclusions and biological interpretations. The majority of ENCODE TFs correlated positively with housekeeping expression, a minority correlated negatively. Thus, housekeeping expression can be understood as a cumulative effect of many types of TF binding sites. This is accompanied by the exclusion of fewer types of binding sites for TFs which are repressors, or support cell lineage commitment or temporarily inducible or spatially-restricted expression.
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Affiliation(s)
- Lukasz Huminiecki
- Instytut Genetyki i Hodowli Zwierząt Polskiej Akademii Nauk, Jastrzębiec, Magdalenka, Poland
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19
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The JAZF1-SUZ12 fusion protein disrupts PRC2 complexes and impairs chromatin repression during human endometrial stromal tumorogenesis. Oncotarget 2018; 8:4062-4078. [PMID: 27845897 PMCID: PMC5354813 DOI: 10.18632/oncotarget.13270] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 10/29/2016] [Indexed: 11/27/2022] Open
Abstract
The Polycomb repressive complex 2 (PRC2), which contains three core proteins EZH2, EED and SUZ12, controls chromatin compaction and transcription repression through trimethylation of lysine 27 on histone 3. The (7;17)(p15;q21) chromosomal translocation present in most cases of endometrial stromal sarcomas (ESSs) results in the in-frame fusion of the JAZF1 and SUZ12 genes. We have investigated whether and how the fusion protein JAZF1-SUZ12 functionally alters PRC2. We found that the fusion protein exists at high levels in ESS containing the t(7;17). Co-transient transfection assay indicated JAZF1-SUZ12 destabilized PRC2 components EZH2 and EED, resulting in decreased histone methyl transferase (HMT) activity, which was confirmed by in vitro studies using reconstituted PRC2 and nucleosome array substrates. We also demonstrated the PRC2 containing the fusion protein decreased the binding affinity to target chromatin loci. In addition, we found that trimethylation of H3K27 was decreased in ESS samples with the t(7;17), but there was no detectable change in H3K9 in these tissues. Moreover, re-expression of SUZ12 in Suz12 (−/−) ES cells rescued the neuronal differentiation while the fusion protein failed to restore this function and enhanced cell proliferation. In summary, our studies reveal that JAZF1-SUZ12 fusion protein disrupts the PRC2 complex, abolishes HMT activity and subsequently activates chromatin/genes normally repressed by PRC2. Such dyesfunction of PRC2 inhibits normal neural differentiation of ES cell and increases cell proliferation. Related changes induced by the JAZF-SUZ12 protein in endometrial stromal cells may explain the oncogenic effect of the t(7;17) in ESS.
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20
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From Flies to Mice: The Emerging Role of Non-Canonical PRC1 Members in Mammalian Development. EPIGENOMES 2018. [DOI: 10.3390/epigenomes2010004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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21
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22
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Huang Y, Chen DH, Liu BY, Shen WH, Ruan Y. Conservation and diversification of polycomb repressive complex 2 (PRC2) proteins in the green lineage. Brief Funct Genomics 2017; 16:106-119. [PMID: 27032420 DOI: 10.1093/bfgp/elw007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The polycomb group (PcG) proteins are key epigenetic regulators of gene expression in animals and plants. They act in multiprotein complexes, of which the best characterized is the polycomb repressive complex 2 (PRC2), which catalyses the trimethylation of histone H3 at lysine 27 (H3K27me3) at chromatin targets. In Arabidopsis thaliana, PRC2 proteins are involved in the regulation of diverse developmental processes, including cell fate determination, vegetative growth and development, flowering time control and embryogenesis. Here, we systematically analysed the evolutionary conservation and diversification of PRC2 components in lower and higher plants. We searched for and identified PRC2 homologues from the sequenced genomes of several green lineage species, from the unicellular green alga Ostreococcus lucimarinus to more complicated angiosperms. We found that some PRC2 core components, e.g. E(z), ESC/FIE and MSI/p55, are ancient and have multiplied coincidently with multicellular evolution. For one component, some members are newly formed, especially in the Cruciferae. During evolution, higher plants underwent copy number multiplication of various PRC2 components, which occurred independently for each component, without any obvious co-amplification of PRC2 members. Among the amplified members, usually one was well-conserved and the others were more diversified. Gene amplification occurred at different times for different PcG members during green lineage evolution. Certain PRC2 core components or members of them were highly conserved. Our study provides an insight into the evolutionary conservation and diversification of PcG proteins and may guide future functional characterization of these important epigenetic regulators in plants other than Arabidopsis.
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Affiliation(s)
- Yong Huang
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-FU-HAU On Plant Epigenome Research, Hunan Agricultural University, Changsha, China.,Key Laboratory of Education, Department of Hunan Province On Plant Genetics and Molecular Biology, Hunan Agricultural University, Changsha, China
| | - Dong-Hong Chen
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-FU-HAU On Plant Epigenome Research, Hunan Agricultural University, Changsha, China.,Key Laboratory of Education, Department of Hunan Province On Plant Genetics and Molecular Biology, Hunan Agricultural University, Changsha, China
| | - Bo-Yu Liu
- Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, Hunan Agricultural University, Changsha, China
| | - Wen-Hui Shen
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-FU-HAU On Plant Epigenome Research, Hunan Agricultural University, Changsha, China.,Institut de Biologie Moléculaire Des Plantes Du CNRS, Université de Strasbourg, 12 Rue Du Général Zimmer, Strasbourg Cedex, France
| | - Ying Ruan
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-FU-HAU On Plant Epigenome Research, Hunan Agricultural University, Changsha, China.,Key Laboratory of Education, Department of Hunan Province On Plant Genetics and Molecular Biology, Hunan Agricultural University, Changsha, China.,Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, Hunan Agricultural University, Changsha, China
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23
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Wang AH, Juan AH, Ko KD, Tsai PF, Zare H, Dell'Orso S, Sartorelli V. The Elongation Factor Spt6 Maintains ESC Pluripotency by Controlling Super-Enhancers and Counteracting Polycomb Proteins. Mol Cell 2017; 68:398-413.e6. [PMID: 29033324 DOI: 10.1016/j.molcel.2017.09.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 06/23/2017] [Accepted: 09/12/2017] [Indexed: 01/07/2023]
Abstract
Spt6 coordinates nucleosome dis- and re-assembly, transcriptional elongation, and mRNA processing. Here, we report that depleting Spt6 in embryonic stem cells (ESCs) reduced expression of pluripotency factors, increased expression of cell-lineage-affiliated developmental regulators, and induced cell morphological and biochemical changes indicative of ESC differentiation. Selective downregulation of pluripotency factors upon Spt6 depletion may be mechanistically explained by its enrichment at ESC super-enhancers, where Spt6 controls histone H3K27 acetylation and methylation and super-enhancer RNA transcription. In ESCs, Spt6 interacted with the PRC2 core subunit Suz12 and prevented H3K27me3 accumulation at ESC super-enhancers and associated promoters. Biochemical as well as functional experiments revealed that Spt6 could compete for binding of the PRC2 methyltransferase Ezh2 to Suz12 and reduce PRC2 chromatin engagement. Thus, in addition to serving as a histone chaperone and transcription elongation factor, Spt6 counteracts repression by opposing H3K27me3 deposition at critical genomic regulatory regions.
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Affiliation(s)
- A Hongjun Wang
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA
| | - Aster H Juan
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA
| | - Kyung Dae Ko
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA
| | - Pei-Fang Tsai
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA
| | - Hossein Zare
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA
| | - Stefania Dell'Orso
- High-Throughput Sequencing Unit, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA
| | - Vittorio Sartorelli
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA.
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24
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Kassis JA, Kennison JA, Tamkun JW. Polycomb and Trithorax Group Genes in Drosophila. Genetics 2017; 206:1699-1725. [PMID: 28778878 PMCID: PMC5560782 DOI: 10.1534/genetics.115.185116] [Citation(s) in RCA: 134] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 05/15/2017] [Indexed: 01/08/2023] Open
Abstract
Polycomb group (PcG) and Trithorax group (TrxG) genes encode important regulators of development and differentiation in metazoans. These two groups of genes were discovered in Drosophila by their opposing effects on homeotic gene (Hox) expression. PcG genes collectively behave as genetic repressors of Hox genes, while the TrxG genes are necessary for HOX gene expression or function. Biochemical studies showed that many PcG proteins are present in two protein complexes, Polycomb repressive complexes 1 and 2, which repress transcription via chromatin modifications. TrxG proteins activate transcription via a variety of mechanisms. Here we summarize the large body of genetic and biochemical experiments in Drosophila on these two important groups of genes.
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Affiliation(s)
- Judith A Kassis
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - James A Kennison
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - John W Tamkun
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064
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25
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Coleman RT, Struhl G. Causal role for inheritance of H3K27me3 in maintaining the OFF state of a Drosophila HOX gene. Science 2017; 356:eaai8236. [PMID: 28302795 PMCID: PMC5595140 DOI: 10.1126/science.aai8236] [Citation(s) in RCA: 140] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 02/03/2017] [Indexed: 12/20/2022]
Abstract
Many eukaryotic cells can respond to transient environmental or developmental stimuli with heritable changes in gene expression that are associated with nucleosome modifications. However, it remains uncertain whether modified nucleosomes play a causal role in transmitting such epigenetic memories, as opposed to controlling or merely reflecting transcriptional states inherited by other means. Here, we provide in vivo evidence that H3K27 trimethylated nucleosomes, once established at a repressed Drosophila HOX gene, remain heritably associated with that gene and can carry the memory of the silenced state through multiple rounds of replication, even when the capacity to copy the H3K27me3 mark to newly incorporated nucleosomes is diminished or abolished. Hence, in this context, the inheritance of H3K27 trimethylation conveys epigenetic memory.
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Affiliation(s)
- Rory T Coleman
- Department of Genetics and Development, Columbia University College of Physicians and Surgeons, 701 West 168th Street, New York, NY 10032, USA
| | - Gary Struhl
- Department of Genetics and Development, Columbia University College of Physicians and Surgeons, 701 West 168th Street, New York, NY 10032, USA.
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26
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Chetverina DA, Elizar’ev PV, Lomaev DV, Georgiev PG, Erokhin MM. Control of the gene activity by polycomb and trithorax group proteins in Drosophila. RUSS J GENET+ 2017. [DOI: 10.1134/s1022795417020028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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27
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H3K27 methylation: a promiscuous repressive chromatin mark. Curr Opin Genet Dev 2016; 43:31-37. [PMID: 27940208 DOI: 10.1016/j.gde.2016.11.001] [Citation(s) in RCA: 164] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 10/21/2016] [Accepted: 11/04/2016] [Indexed: 12/24/2022]
Abstract
Polycomb Repressive Complex 2 (PRC2) is a multiprotein complex that catalyzes the methylation of lysine 27 on histone H3 (H3K27me). This histone modification is a feature of facultative heterochromatin in many eukaryotes and maintains transcriptional repression established during early development. Understanding how PRC2 targets regions of the genome to be methylated remains poorly understood. Different cell types can show disparate patterns of H3K27me, and chromatin perturbations, such as loss of marks of constitutive heterochromatin, can cause redistribution of H3K27me, implying that DNA sequence, per se, is not sufficient to define the distribution of this mark. Emerging information supports the idea that the chromatin context-including histone modifications, DNA methylation, transcription, chromatin structure and organization within the nucleus-informs PRC2 target selection.
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28
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Oliva M, Butenko Y, Hsieh TF, Hakim O, Katz A, Smorodinsky NI, Michaeli D, Fischer RL, Ohad N. FIE, a nuclear PRC2 protein, forms cytoplasmic complexes in Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:6111-6123. [PMID: 27811080 PMCID: PMC5100023 DOI: 10.1093/jxb/erw373] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Polycomb group (PcG) proteins are evolutionarily conserved chromatin modifiers that regulate developmental pathways in plants. PcGs form nuclear multi-subunit Polycomb Repressive Complexes (PRCs). The PRC2 complex mediates gene repression via methylation of lysine 27 on histone H3, which consequently leads to chromatin condensation. In Arabidopsis thaliana, several PRC2 complexes with different compositions were identified, each controlling a particular developmental program.The core subunit FIE is crucial for PRC2 function throughout the plant life cycle, yet accurate information on its spatial and temporal localization was absent. This study focused on identifying FIE accumulation patterns, using microscopy and biochemical approaches. Analysing endogenous FIE and transgenic gFIE-green fluorescent protein fusion protein (gFIE-GFP) showed that FIE accumulates in the nuclei of every cell type examined. Interestingly, gFIE-GFP, as well as the endogenous FIE, also localized to the cytoplasm in all examined tissues. In both vegetative and reproductive organs, FIE formed cytoplasmic high-molecular-mass complexes, in parallel to the nuclear PRC2 complexes. Moreover, size-exclusion chromatography and bimolecular fluorescence complementation assays indicated that in inflorescences FIE formed a cytoplasmic complex with MEA, a PRC2 histone methyltransferase subunit. In contrast, CLF and SWN histone methyltransferases were strictly nuclear. Presence of PRC2 subunits in cytoplasmic complexes has not been previously described in plants. Our findings are in agreement with accumulating evidence demonstrating cytoplasmic localization and function of PcGs in metazoa. The cytosolic accumulation of PRC2 components in plants supports the model that PcGs have alternative non-nuclear functions that go beyond chromatin methylation.
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Affiliation(s)
- Moran Oliva
- Department of Molecular Biology and Ecology of Plant, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
- Department of Ornamental Horticulture and Plant Biotechnology, Agriculture Research Organization, The Volcani Center, PO Box 6, Beit Dagan, 50250, Israel
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Yana Butenko
- Department of Molecular Biology and Ecology of Plant, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
- Department of Plant Sciences, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, 76100, Israel
| | - Tzung-Fu Hsieh
- Plants for Human Health Institute, and Department of Plant and Microbial Biology, North Carolina State University, Kannapolis, NC 28081, USA
| | - Ofir Hakim
- Department of Molecular Biology and Ecology of Plant, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - Aviva Katz
- Department of Molecular Biology and Ecology of Plant, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Nechama I Smorodinsky
- Department of Cell Research and Immunology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Daphna Michaeli
- Department of Molecular Biology and Ecology of Plant, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Robert L Fischer
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA
| | - Nir Ohad
- Department of Molecular Biology and Ecology of Plant, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
- The Manna Center Program for Food Safety and Security, Tel Aviv University, 69978, Israel
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29
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Kahn TG, Dorafshan E, Schultheis D, Zare A, Stenberg P, Reim I, Pirrotta V, Schwartz YB. Interdependence of PRC1 and PRC2 for recruitment to Polycomb Response Elements. Nucleic Acids Res 2016; 44:10132-10149. [PMID: 27557709 PMCID: PMC5137424 DOI: 10.1093/nar/gkw701] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 07/26/2016] [Accepted: 07/28/2016] [Indexed: 12/31/2022] Open
Abstract
Polycomb Group (PcG) proteins are epigenetic repressors essential for control of development and cell differentiation. They form multiple complexes of which PRC1 and PRC2 are evolutionary conserved and obligatory for repression. The targeting of PRC1 and PRC2 is poorly understood and was proposed to be hierarchical and involve tri-methylation of histone H3 (H3K27me3) and/or monoubiquitylation of histone H2A (H2AK118ub). Here, we present a strict test of this hypothesis using the Drosophila model. We discover that neither H3K27me3 nor H2AK118ub is required for targeting PRC complexes to Polycomb Response Elements (PREs). We find that PRC1 can bind PREs in the absence of PRC2 but at many PREs PRC2 requires PRC1 to be targeted. We show that one role of H3K27me3 is to allow PcG complexes anchored at PREs to interact with surrounding chromatin. In contrast, the bulk of H2AK118ub is unrelated to PcG repression. These findings radically change our view of how PcG repression is targeted and suggest that PRC1 and PRC2 can communicate independently of histone modifications.
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Affiliation(s)
- Tatyana G Kahn
- Department of Molecular Biology, Umeå University, Umeå, 901 87, Sweden
| | - Eshagh Dorafshan
- Department of Molecular Biology, Umeå University, Umeå, 901 87, Sweden
| | - Dorothea Schultheis
- Friedrich-Alexander University of Erlangen-Nürnberg, Department of Biology, Division of Developmental Biology, Erlangen, D-91058, Germany
| | - Aman Zare
- Department of Molecular Biology, Umeå University, Umeå, 901 87, Sweden
| | - Per Stenberg
- Department of Molecular Biology, Umeå University, Umeå, 901 87, Sweden.,Division of CBRN Defense and Security, Swedish Defense Research Agency, FOI, Umeå, 906 21, Sweden
| | - Ingolf Reim
- Friedrich-Alexander University of Erlangen-Nürnberg, Department of Biology, Division of Developmental Biology, Erlangen, D-91058, Germany
| | - Vincenzo Pirrotta
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854, USA
| | - Yuri B Schwartz
- Department of Molecular Biology, Umeå University, Umeå, 901 87, Sweden
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Hrzenjak A. JAZF1/SUZ12 gene fusion in endometrial stromal sarcomas. Orphanet J Rare Dis 2016; 11:15. [PMID: 26879382 PMCID: PMC4754953 DOI: 10.1186/s13023-016-0400-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 02/08/2016] [Indexed: 12/11/2022] Open
Abstract
Endometrial stromal sarcomas (ESSs) belong to the rarest uterine malignancies (prevalence category <1-9/1,000,000). According to the new 2014 World Health Organisation (WHO) classification, they are separated into four categories; benign endometrial stromal nodules (ESNs), low grade endometrial stromal sarcomas (LG-ESSs), high-grade endometrial stromal sarcomas (HG-ESSs) and undifferentiated uterine sarcomas (UUSs). Due to heterogeneous histopathologic appearance these tumors still represent diagnostic challenge, even for experienced pathologists. ESSs are genetically very heterogeneous and several chromosomal translocations and gene fusions have so far been identified in these malignancies. To date the JAZF1/SUZ12 gene fusion is by far the most frequent and seems to be the cytogenetic hallmark of ESN and LG-ESS. Based on present literature data this gene fusion is present in approximately 75 % of ESN, 50 % of LG-ESS and 15 % of HG-ESS cases. The frequency of JAZF1/SUZ12 appearance varies between classic ESS and different morphologic variants. This gene fusion is suggested to become a specific diagnostic tool, especially in difficult borderline cases. In combination with the recently described YWHAE/FAM22 gene fusion the JAZF1/SUZ12 fusion could be used to differentiate between LG-ESS and HG-ESS. The purpose of this review is to summarize literature data published in last two and a half decades about this gene fusion, as a contribution to our understanding of ESS genetics and pathogenesis.
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Affiliation(s)
- Andelko Hrzenjak
- Department of Internal Medicine, Division of Pulmonology, Medical University of Graz, Auenbruggerplatz 15, A-8036, Graz, Austria. .,Ludwig Boltzmann Institute for Lung Vascular Research, Medical University of Graz, Graz, Austria.
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Yung P, Stuetzer A, Fischle W, Martinez AM, Cavalli G. Histone H3 Serine 28 Is Essential for Efficient Polycomb-Mediated Gene Repression in Drosophila. Cell Rep 2015; 11:1437-45. [DOI: 10.1016/j.celrep.2015.04.055] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Revised: 03/31/2015] [Accepted: 04/25/2015] [Indexed: 10/23/2022] Open
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Matsuoka Y, Bando T, Watanabe T, Ishimaru Y, Noji S, Popadić A, Mito T. Short germ insects utilize both the ancestral and derived mode of Polycomb group-mediated epigenetic silencing of Hox genes. Biol Open 2015; 4:702-9. [PMID: 25948756 PMCID: PMC4467190 DOI: 10.1242/bio.201411064] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In insect species that undergo long germ segmentation, such as Drosophila, all segments are specified simultaneously at the early blastoderm stage. As embryogenesis progresses, the expression boundaries of Hox genes are established by repression of gap genes, which is subsequently replaced by Polycomb group (PcG) silencing. At present, however, it is not known whether patterning occurs this way in a more ancestral (short germ) mode of embryogenesis, where segments are added gradually during posterior elongation. In this study, two members of the PcG family, Enhancer of zeste (E(z)) and Suppressor of zeste 12 (Su(z)12), were analyzed in the short germ cricket, Gryllus bimaculatus. Results suggest that although stepwise negative regulation by gap and PcG genes is present in anterior members of the Hox cluster, it does not account for regulation of two posterior Hox genes, abdominal-A (abd-A) and Abdominal-B (Abd-B). Instead, abd-A and Abd-B are predominantly regulated by PcG genes, which is the mode present in vertebrates. These findings suggest that an intriguing transition of the PcG-mediated silencing of Hox genes may have occurred during animal evolution. The ancestral bilaterian state may have resembled the current vertebrate mode of regulation, where PcG-mediated silencing of Hox genes occurs before their expression is initiated and is responsible for the establishment of individual expression domains. Then, during insect evolution, the repression by transcription factors may have been acquired in anterior Hox genes of short germ insects, while PcG silencing was maintained in posterior Hox genes.
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Affiliation(s)
- Yuji Matsuoka
- Department of Life Systems, Institute of Technology and Science, The University of Tokushima Graduate School, 2-1 Minami-Jyosanjima-cho, Tokushima City, Tokushima 770-8506, Japan
| | - Tetsuya Bando
- Department of Life Systems, Institute of Technology and Science, The University of Tokushima Graduate School, 2-1 Minami-Jyosanjima-cho, Tokushima City, Tokushima 770-8506, Japan Present address: Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Kita-ku, Okayama city, Okayama, 700-8530, Japan
| | - Takahito Watanabe
- Center for Collaboration among Agriculture, Industry and Commerce, The University of Tokushima, 2-24 Shinkura-cho, Tokushima City, Tokushima 770-8501, Japan
| | - Yoshiyasu Ishimaru
- Department of Life Systems, Institute of Technology and Science, The University of Tokushima Graduate School, 2-1 Minami-Jyosanjima-cho, Tokushima City, Tokushima 770-8506, Japan
| | - Sumihare Noji
- Center for Collaboration among Agriculture, Industry and Commerce, The University of Tokushima, 2-24 Shinkura-cho, Tokushima City, Tokushima 770-8501, Japan
| | - Aleksandar Popadić
- Biological Sciences Department, Wayne State University, Detroit, MI 48202, USA
| | - Taro Mito
- Department of Life Systems, Institute of Technology and Science, The University of Tokushima Graduate School, 2-1 Minami-Jyosanjima-cho, Tokushima City, Tokushima 770-8506, Japan
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Cabrera JR, Olcese U, Horabin JI. A balancing act: heterochromatin protein 1a and the Polycomb group coordinate their levels to silence chromatin in Drosophila. Epigenetics Chromatin 2015; 8:17. [PMID: 25954320 PMCID: PMC4423169 DOI: 10.1186/s13072-015-0010-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 04/15/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The small non-histone protein Heterochromatin protein 1a (HP1a) plays a vital role in packaging chromatin, most notably in forming constitutive heterochromatin at the centromeres and telomeres. A second major chromatin regulating system is that of the Polycomb/trithorax groups of genes which, respectively, maintain the repressed/activated state of euchromatin. Recent analyses suggest they affect the expression of a multitude of genes, beyond the homeotics whose alteration in expression lead to their initial discovery. RESULTS Our data suggest that early in Drosophila development, HP1a collaborates with the Polycomb/trithorax groups of proteins to regulate gene expression and that the two chromatin systems do not act separately as convention describes. HP1a affects the levels of both the Polycomb complexes and RNA polymerase II at promoters, as assayed by chromatin immunoprecipitation analysis. Deposition of both the repressive (H3K27me3) and activating (H3K4me3) marks promoted by the Polycomb/trithorax group genes at gene promoters is affected. Additionally, depending on which parent contributes the null mutation of the HP1a gene, the levels of the H3K27me3 and H3K9me3 silencing marks at both promoters and heterochromatin are different. Changes in levels of the H3K27me3 and H3K9me3 repressive marks show a mostly reciprocal nature. The time around the mid-blastula transition, when the zygotic genome begins to be actively transcribed, appears to be a transition/decision point for setting the levels. CONCLUSIONS We find that HP1a, which is normally critical for the formation of constitutive heterochromatin, also affects the generation of the epigenetic marks of the Polycomb/trithorax groups of proteins, chromatin modifiers which are key to maintaining gene expression in euchromatin. At gene promoters, deposition of both the repressive H3K27me3 and activating H3K4me3 marks of histone modifications shows a dependence on HP1a. Around the mid-blastula transition, when the zygotic genome begins to be actively transcribed, a pivotal decision for the level of silencing appears to take place. This is also when the embryo organizes its genome into heterochromatin and euchromatin. A balance between the HP1a and Polycomb group silencing systems appears to be set for the chromatin types that each system will primarily regulate.
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Affiliation(s)
- Janel R Cabrera
- Department of Biomedical Sciences, College of Medicine, Florida State University, Rm 3300-G, 1115 W, Call St., Tallahassee, FL 32306 USA ; Current Address: Center for Life Sciences, Department of Medicine, Division of Cardiology, Beth Israel Deaconess Medical Center, Rm 917, 3 Blackfan Circle, Boston, MA 02215 USA
| | - Ursula Olcese
- Department of Biomedical Sciences, College of Medicine, Florida State University, Rm 3300-G, 1115 W, Call St., Tallahassee, FL 32306 USA
| | - Jamila I Horabin
- Department of Biomedical Sciences, College of Medicine, Florida State University, Rm 3300-G, 1115 W, Call St., Tallahassee, FL 32306 USA
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Bajusz I, Sipos L, Pirity MK. Nucleotide substitutions revealing specific functions of Polycomb group genes. Mol Genet Metab 2015; 114:547-56. [PMID: 25669595 DOI: 10.1016/j.ymgme.2015.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 01/22/2015] [Indexed: 01/22/2023]
Abstract
POLYCOMB group (PCG) proteins belong to the family of epigenetic regulators of genes playing important roles in differentiation and development. Mutants of PcG genes were isolated first in the fruit fly, Drosophila melanogaster, resulting in spectacular segmental transformations due to the ectopic expression of homeotic genes. Homologs of Drosophila PcG genes were also identified in plants and in vertebrates and subsequent experiments revealed the general role of PCG proteins in the maintenance of the repressed state of chromatin through cell divisions. The past decades of gene targeting experiments have allowed us to make significant strides towards understanding how the network of PCG proteins influences multiple aspects of cellular fate determination during development. Being involved in the transmission of specific expression profiles of different cell lineages, PCG proteins were found to control wide spectra of unrelated epigenetic processes in vertebrates, such as stem cell plasticity and renewal, genomic imprinting and inactivation of X-chromosome. PCG proteins also affect regulation of metabolic genes being important for switching programs between pluripotency and differentiation. Insight into the precise roles of PCG proteins in normal physiological processes has emerged from studies employing cell culture-based systems and genetically modified animals. Here we summarize the findings obtained from PcG mutant fruit flies and mice generated to date with a focus on PRC1 and PRC2 members altered by nucleotide substitutions resulting in specific alleles. We also include a compilation of lessons learned from these models about the in vivo functions of this complex protein family. With multiple knockout lines, sophisticated approaches to study the consequences of peculiar missense point mutations, and insights from complementary gain-of-function systems in hand, we are now in a unique position to significantly advance our understanding of the molecular basis of in vivo functions of PcG proteins.
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Affiliation(s)
- Izabella Bajusz
- Biological Research Centre, Hungarian Academy of Sciences, Institute of Genetics, H-6701 Szeged, Hungary.
| | - László Sipos
- Biological Research Centre, Hungarian Academy of Sciences, Institute of Genetics, H-6701 Szeged, Hungary
| | - Melinda K Pirity
- Biological Research Centre, Hungarian Academy of Sciences, Institute of Genetics, H-6701 Szeged, Hungary
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Jividen K, Li H. Chimeric RNAs generated by intergenic splicing in normal and cancer cells. Genes Chromosomes Cancer 2014; 53:963-71. [PMID: 25131334 DOI: 10.1002/gcc.22207] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 07/16/2014] [Indexed: 12/30/2022] Open
Abstract
A hallmark of many neoplasias is chromosomal rearrangement, an event that commonly results in the fusion of two separate genes. The RNA and protein resulting from these gene fusions often play critical roles in cancer development, maintenance, and progression. Traditionally, these fusion products are thought to be produced solely due to DNA level changes and are therefore considered unique to cancer. Recent advances in microarray and deep-sequencing have revealed many more fusion transcripts. Surprisingly, some are without detectable rearrangement at the DNA level. Reports have demonstrated that at least some of these chimeric RNAs are generated via intergenic splicing. In this review, we highlight three examples of these noncanonical chimeric transcripts that are formed by trans-splicing or cis-splicing of adjacent genes and summarize the knowledge we have regarding these noncanonical fusions. We discuss the implications of the chimeric RNAs in both cancer and normal physiology, as some of these fusion transcripts are found in normal, noncancerous cells with sequences identical to those generated by canonical chromosomal translocation found in cancer cells. Finally, we present methods that are currently being used to discover additional chimeric RNAs.
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Affiliation(s)
- Kasey Jividen
- Department of Pathology, University of Virginia, Charlottesville, VA
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Yamagishi J, Natori A, Tolba MEM, Mongan AE, Sugimoto C, Katayama T, Kawashima S, Makalowski W, Maeda R, Eshita Y, Tuda J, Suzuki Y. Interactive transcriptome analysis of malaria patients and infecting Plasmodium falciparum. Genome Res 2014; 24:1433-44. [PMID: 25091627 PMCID: PMC4158759 DOI: 10.1101/gr.158980.113] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
To understand the molecular mechanisms of parasitism in vivo, it is essential to elucidate how the transcriptomes of the human hosts and the infecting parasites affect one another. Here we report the RNA-seq analysis of 116 Indonesian patients infected with the malaria parasite Plasmodium falciparum (Pf). We extracted RNAs from their peripheral blood as a mixture of host and parasite transcripts and mapped the RNA-seq tags to the human and Pf reference genomes to separate the respective tags. We were thus able to simultaneously analyze expression patterns in both humans and parasites. We identified human and parasite genes and pathways that correlated with various clinical data, which may serve as primary targets for drug developments. Of particular importance, we revealed characteristic expression changes in the human innate immune response pathway genes including TLR2 and TICAM2 that correlated with the severity of the malaria infection. We also found a group of transcription regulatory factors, JUND, for example, and signaling molecules, TNFAIP3, for example, that were strongly correlated in the expression patterns of humans and parasites. We also identified several genetic variations in important anti-malaria drug resistance-related genes. Furthermore, we identified the genetic variations which are potentially associated with severe malaria symptoms both in humans and parasites. The newly generated data should collectively lay a unique foundation for understanding variable behaviors of the field malaria parasites, which are far more complex than those observed under laboratory conditions.
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Affiliation(s)
- Junya Yamagishi
- Tohoku Medical Megabank Organization, Tohoku University, Sendai, Miyagi 980-8579, Japan; Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Anna Natori
- Department of Medical Genome Sciences, University of Tokyo, Kashiwa, Chiba 277-8562, Japan
| | | | - Arthur E Mongan
- Department of Medicine, Sam Ratulangi University, Kampus Unsrat, Bahu Manado, 95115, Indonesia
| | - Chihiro Sugimoto
- Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Toshiaki Katayama
- Database Center for Life Science (DBCLS), Research Organization of Information and Systems (ROIS), The University of Tokyo Bunkyo-ku, Tokyo 113-0032, Japan
| | - Shuichi Kawashima
- Database Center for Life Science (DBCLS), Research Organization of Information and Systems (ROIS), The University of Tokyo Bunkyo-ku, Tokyo 113-0032, Japan
| | - Wojciech Makalowski
- Institute of Bioinformatics, Faculty of Medicine, University of Muenster, 48149 Munster, Germany
| | - Ryuichiro Maeda
- Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Yuki Eshita
- Oita University, School of Medicine, Yufushi, Oita 879-5593, Japan
| | - Josef Tuda
- Department of Medicine, Sam Ratulangi University, Kampus Unsrat, Bahu Manado, 95115, Indonesia
| | - Yutaka Suzuki
- Department of Medical Genome Sciences, University of Tokyo, Kashiwa, Chiba 277-8562, Japan;
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Steffen PA, Ringrose L. What are memories made of? How Polycomb and Trithorax proteins mediate epigenetic memory. Nat Rev Mol Cell Biol 2014; 15:340-56. [PMID: 24755934 DOI: 10.1038/nrm3789] [Citation(s) in RCA: 249] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In any biological system with memory, the state of the system depends on its history. Epigenetic memory maintains gene expression states through cell generations without a change in DNA sequence and in the absence of initiating signals. It is immensely powerful in biological systems - it adds long-term stability to gene expression states and increases the robustness of gene regulatory networks. The Polycomb group (PcG) and Trithorax group (TrxG) proteins can confer long-term, mitotically heritable memory by sustaining silent and active gene expression states, respectively. Several recent studies have advanced our understanding of the molecular mechanisms of this epigenetic memory during DNA replication and mitosis.
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Affiliation(s)
- Philipp A Steffen
- Institute of Molecular Biotechnology (IMBA), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Leonie Ringrose
- Institute of Molecular Biotechnology (IMBA), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
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McElroy KA, Kang H, Kuroda MI. Are we there yet? Initial targeting of the Male-Specific Lethal and Polycomb group chromatin complexes in Drosophila. Open Biol 2014; 4:140006. [PMID: 24671948 PMCID: PMC3971409 DOI: 10.1098/rsob.140006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Chromatin-binding proteins must navigate the complex nuclear milieu to find their sites of action, and a constellation of protein factors and other properties are likely to influence targeting specificity. Despite considerable progress, the precise rules by which binding specificity is achieved have remained elusive. Here, we consider early targeting events for two groups of chromatin-binding complexes in Drosophila: the Male-Specific Lethal (MSL) and the Polycomb group (PcG) complexes. These two serve as models for understanding targeting, because they have been extensively studied and play vital roles in Drosophila, and their targets have been documented at high resolution. Furthermore, the proteins and biochemical properties of both complexes are largely conserved in multicellular organisms, including humans. While the MSL complex increases gene expression and PcG members repress genes, the two groups share many similarities such as the ability to modify their chromatin environment to create active or repressive domains, respectively. With legacies of in-depth genetic, biochemical and now genomic approaches, the MSL and PcG complexes will continue to provide tractable systems for understanding the recruitment of multiprotein chromatin complexes to their target loci.
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Affiliation(s)
- Kyle A McElroy
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
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Mussotter T, Bengesser K, Högel J, Cooper DN, Kehrer-Sawatzki H. Population-specific differences in gene conversion patterns between human SUZ12 and SUZ12P are indicative of the dynamic nature of interparalog gene conversion. Hum Genet 2014; 133:383-401. [PMID: 24385046 DOI: 10.1007/s00439-013-1410-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 12/08/2013] [Indexed: 11/29/2022]
Abstract
Nonallelic homologous gene conversion (NAHGC) resulting from interparalog recombination without crossover represents an important influence on the evolution of duplicated sequences in the human genome. In 17q11.2, different paralogous sequences mediate large NF1 deletions by nonallelic homologous recombination with crossover (NAHR). Among these paralogs are SUZ12 and its pseudogene SUZ12P which harbour the breakpoints of type-2 (1.2-Mb) NF1 deletions. Such deletions are caused predominantly by mitotic NAHR since somatic mosaicism with normal cells is evident in most patients. Investigating whether SUZ12 and SUZ12P have also been involved in NAHGC, we observed gene conversion tracts between these paralogs in both Africans (AFR) and Europeans (EUR). Since germline type-2 NF1 deletions resulting from meiotic NAHR are very rare, the vast majority of the gene conversion tracts in SUZ12 and SUZ12P are likely to have resulted from mitotic recombination during premeiotic cell divisions of germ cells. A higher number of gene conversion tracts were noted within SUZ12 and SUZ12P in AFR as compared to EUR. Further, the distinctive signature of NAHGC (a high number of SNPs per paralog and a high number of shared SNPs between paralogs), a characteristic of many actively recombining paralogs, was observed in both SUZ12 and SUZ12P but only in AFR and not in EUR. A novel polymorphic 2.3-kb deletion in SUZ12P was identified which exhibited a high allele frequency in EUR. We postulate that this interparalog structural difference, together with low allelic recombination rates, could have caused a reduction in NAHGC between SUZ12 and SUZ12P during human evolution.
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Affiliation(s)
- Tanja Mussotter
- Institute of Human Genetics, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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40
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Copur Ö, Müller J. The histone H3-K27 demethylase Utx regulates HOX gene expression in Drosophila in a temporally restricted manner. Development 2013; 140:3478-85. [PMID: 23900545 PMCID: PMC3912917 DOI: 10.1242/dev.097204] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Trimethylation of histone H3 at lysine 27 (H3-K27me3) by Polycomb repressive complex 2 (PRC2) is a key step for transcriptional repression by the Polycomb system. Demethylation of H3-K27me3 by Utx and/or its paralogs has consequently been proposed to be important for counteracting Polycomb repression. To study the phenotype of Drosophila mutants that lack H3-K27me3 demethylase activity, we created UtxΔ, a deletion allele of the single Drosophila Utx gene. UtxΔ homozygotes that contain maternally deposited wild-type Utx protein develop into adults with normal epidermal morphology but die shortly after hatching. By contrast, UtxΔ homozygotes that are derived from Utx mutant germ cells and therefore lack both maternal and zygotic Utx protein, die as larvae and show partial loss of expression of HOX genes in tissues in which these genes are normally active. This phenotype classifies Utx as a trithorax group regulator. We propose that Utx is needed in the early embryo to prevent inappropriate instalment of long-term Polycomb repression at HOX genes in cells in which these genes must be kept active. In contrast to PRC2, which is essential for, and continuously required during, germ cell, embryonic and larval development, Utx therefore appears to have a more limited and specific function during development. This argues against a continuous interplay between H3-K27me3 methylation and demethylation in the control of gene transcription in Drosophila. Furthermore, our analyses do not support the recent proposal that Utx would regulate cell proliferation in Drosophila as Utx mutant cells generated in wild-type animals proliferate like wild-type cells.
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Affiliation(s)
- Ömer Copur
- MPI of Biochemistry, Chromatin and Chromosome Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
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41
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Elements of the polycomb repressor SU(Z)12 needed for histone H3-K27 methylation, the interface with E(Z), and in vivo function. Mol Cell Biol 2013; 33:4844-56. [PMID: 24100017 DOI: 10.1128/mcb.00307-13] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Polycomb repressive complex 2 (PRC2) is an essential chromatin-modifying enzyme that implements gene silencing. PRC2 methylates histone H3 on lysine-27 and is conserved from plants to flies to humans. In Drosophila melanogaster, PRC2 contains four core subunits: E(Z), SU(Z)12, ESC, and NURF55. E(Z) bears a SET domain that houses the enzyme active site. However, PRC2 activity depends upon critical inputs from SU(Z)12 and ESC. The stimulatory mechanisms are not understood. We present here functional dissection of the SU(Z)12 subunit. SU(Z)12 contains two highly conserved domains: an ∼140-amino-acid VEFS domain and a Cys2-His2 zinc finger (ZnF). Analysis of recombinant PRC2 bearing VEFS domain alterations, including some modeled after leukemia mutations, identifies distinct elements needed for SU(Z)12 assembly with E(Z) and stimulation of histone methyltransferase. The results define an extensive VEFS subdomain that organizes the SU(Z)12-E(Z) interface. Although the SU(Z)12 ZnF is not needed for methyltransferase in vitro, genetic rescue assays show that the ZnF is required in vivo. Chromatin immunoprecipitations reveal that this ZnF facilitates PRC2 binding to a genomic target. This study defines functionally critical SU(Z)12 elements, including key determinants of SU(Z)12-E(Z) communication. Together with recent findings, this illuminates PRC2 modulation by conserved inputs from its noncatalytic subunits.
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Iovino N, Ciabrelli F, Cavalli G. PRC2 controls Drosophila oocyte cell fate by repressing cell cycle genes. Dev Cell 2013; 26:431-9. [PMID: 23932903 DOI: 10.1016/j.devcel.2013.06.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 06/03/2013] [Accepted: 06/19/2013] [Indexed: 01/08/2023]
Abstract
The oocyte is a unique cell type that undergoes extensive chromosome changes on its way to fertilization, but the chromatin determinants of its fate are unknown. Here, we show that Polycomb group (PcG) proteins of the Polycomb repressive complex 2 (PRC2) determine the fate of the oocyte in Drosophila. Mutation of the enzymatic PRC2 subunit Enhancer of zeste (E(z)) in the germline abolishes spatial and temporal control of the cell cycle and induces sterility via transdetermination of the oocyte into a nurse-like cell. This fate switch depends on loss of silencing of two PRC2 target genes, Cyclin E and the cyclin-dependent kinase inhibitor dacapo. By contrast, the PRC1 component Polycomb (Pc) plays no role in this process. Our results demonstrate that PRC2 plays an exquisite role in the determination of the oocyte fate by preventing its switching into an endoreplicative program.
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Affiliation(s)
- Nicola Iovino
- Institut de Génétique Humaine, CNRS, 141 rue de la Cardonille, Montpellier 34396, France
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43
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Golbabapour S, Majid NA, Hassandarvish P, Hajrezaie M, Abdulla MA, Hadi AHA. Gene silencing and Polycomb group proteins: an overview of their structure, mechanisms and phylogenetics. OMICS : A JOURNAL OF INTEGRATIVE BIOLOGY 2013; 17:283-96. [PMID: 23692361 PMCID: PMC3662373 DOI: 10.1089/omi.2012.0105] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
DNA methylation, histone modifications, and chromatin configuration are crucially important in the regulation of gene expression. Among these epigenetic mechanisms, silencing the expression of certain genes depending on developmental stage and tissue specificity is a key repressive system in genome programming. Polycomb (Pc) proteins play roles in gene silencing through different mechanisms. These proteins act in complexes and govern the histone methylation profiles of a large number of genes that regulate various cellular pathways. This review focuses on two main Pc complexes, Pc repressive complexes 1 and 2, and their phylogenetic relationship, structures, and function. The dynamic roles of these complexes in silencing will be discussed herein, with a focus on the recruitment of Pc complexes to target genes and the key factors involved in their recruitment.
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Affiliation(s)
- Shahram Golbabapour
- Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
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Mason-Suares H, Tie F, Yan CM, Harte PJ. Polycomb silencing of the Drosophila 4E-BP gene regulates imaginal disc cell growth. Dev Biol 2013; 380:111-24. [PMID: 23523430 DOI: 10.1016/j.ydbio.2013.03.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 02/15/2013] [Accepted: 03/04/2013] [Indexed: 12/14/2022]
Abstract
Polycomb group (PcG) proteins are best known for their role in maintaining stable, mitotically heritable silencing of the homeotic (HOX) genes during development. In addition to loss of homeotic gene silencing, some PcG mutants also have small imaginal discs. These include mutations in E(z), Su(z)12, esc and escl, which encode Polycomb repressive complex 2 (PRC2) subunits. The cause of this phenotype is not known, but the human homologs of PRC2 subunits have been shown to play a role in cell proliferation, are over-expressed in many tumors, and appear to be required for tumor proliferation. Here we show that the small imaginal disc phenotype arises, at least in part, from a cell growth defect. In homozygous E(z) mutants, imaginal disc cells are smaller than cells in normally proliferating discs. We show that the Thor gene, which encodes eIF4E-binding protein (4E-BP), the evolutionarily conserved inhibitor of cap-dependent translation and potent inhibitor of cell growth, is involved in the development of this phenotype. The Thor promoter region contains DNA binding motifs for transcription factors found in well-characterized Polycomb response elements (PREs), including PHO/PHOL, GAGA factor, and others, suggesting that Thor may be a direct target of Polycomb silencing. We present chromatin immunoprecipitation evidence that PcG proteins are bound to the Thor 5' region in vivo. The Thor gene is normally repressed in imaginal discs, but Thor mRNA and 4E-BP protein levels are elevated in imaginal discs of PRC2 subunit mutant larvae. Deletion of the Thor gene in E(z) mutants partially restores imaginal disc size toward wild-type and results in an increase in the fraction of larvae that pupariate. These results thus suggest that PcG proteins can directly modulate cell growth in Drosophila, in part by regulating Thor expression.
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Affiliation(s)
- Heather Mason-Suares
- Department of Genetics and Genome Sciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA
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Yuan W, Wu T, Fu H, Dai C, Wu H, Liu N, Li X, Xu M, Zhang Z, Niu T, Han Z, Chai J, Zhou XJ, Gao S, Zhu B. Dense chromatin activates Polycomb repressive complex 2 to regulate H3 lysine 27 methylation. Science 2012; 337:971-5. [PMID: 22923582 DOI: 10.1126/science.1225237] [Citation(s) in RCA: 202] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Polycomb repressive complex 2 (PRC2)-mediated histone H3 lysine 27 (H3K27) methylation is vital for Polycomb gene silencing, a classic epigenetic phenomenon that maintains transcriptional silencing throughout cell divisions. We report that PRC2 activity is regulated by the density of its substrate nucleosome arrays. Neighboring nucleosomes activate the PRC2 complex with a fragment of their H3 histones (Ala(31) to Arg(42)). We also identified mutations on PRC2 subunit Su(z)12, which impair its binding and response to the activating peptide and its ability in establishing H3K27 trimethylation levels in vivo. In mouse embryonic stem cells, local chromatin compaction occurs before the formation of trimethylated H3K27 upon transcription cessation of the retinoic acid-regulated gene CYP26a1. We propose that PRC2 can sense the chromatin environment to exert its role in the maintenance of transcriptional states.
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Affiliation(s)
- Wen Yuan
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
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Scheuermann JC, Gutiérrez L, Müller J. Histone H2A monoubiquitination and Polycomb repression: the missing pieces of the puzzle. Fly (Austin) 2012; 6:162-8. [PMID: 22836728 DOI: 10.4161/fly.20986] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Polycomb group (PcG) proteins were originally identified as negative regulators of HOX genes in Drosophila but have since emerged as a widely used transcriptional repression system that controls a variety of developmental processes in animals and plants. PcG proteins exist in multi-protein complexes that comprise specific chromatin-modifying enzymatic activities. Genome-wide binding studies in Drosophila and in mammalian cells revealed that these complexes co-localize at a large set of genes encoding developmental regulators. Recent analyses in Drosophila have begun to explore how the different chromatin-modifying activities of PcG protein complexes contribute to the repression of individual target genes. These studies suggest that monoubiquitination of histone H2A (H2Aub) by the PcG protein Sce is only essential for repression of a subset of PcG target genes but is not required for the Polycomb-mediated repression of other targets. Calypso/dBap1, a major deubiquitinase for H2Aub is also critically needed for repression of a subset of PcG target genes. Here, we review our current understanding of the role of H2A monoubiquitination and deubiquitination in Polycomb repression in Drosophila. We discuss unresolved issues concerning the immunological detection of H2Aub and critically evaluate experiments that used Sce and Ring1B point mutants with impaired H2A ubiquitinase activity to study H2Aub-dependent and -independent functions of these proteins in transcriptional repression.
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Affiliation(s)
- Johanna C Scheuermann
- Department of Chromatin and Chromosome Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
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Inner workings and regulatory inputs that control Polycomb repressive complex 2. Chromosoma 2012; 121:221-34. [PMID: 22349693 DOI: 10.1007/s00412-012-0361-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 01/09/2012] [Accepted: 01/10/2012] [Indexed: 01/27/2023]
Abstract
Polycomb repressive complex 2 (PRC2) is a conserved multisubunit enzyme that methylates histone H3 on lysine-27. This chromatin modification is a hallmark of target genes transcriptionally silenced by the Polycomb system. At its core, PRC2 activity depends upon the SET domain active site of its catalytic subunit, EZH2, as well as critical stimulatory inputs from noncatalytic subunits, especially EED and SU(Z)12. We review recent progress on this core PRC2 machinery, including key features of the active site, control mechanisms that operate via EZH2 phosphorylation, and subunit elements and architectures that influence PRC2 function. Among these, we highlight work identifying an EED regulatory site that enables PRC2 to bind pre-existing methylated H3-K27 and stimulate enzyme output. These advances illuminate basic inner workings of PRC2 and also provide insights that could aid design of PRC2 inhibitors. The chromatin landscape that PRC2 encounters in vivo is decorated with many histone modifications that accompany active transcription, such as H3-K4 methylation. It has long been assumed that these "active" modifications oppose PRC2 at some level but, until recently, mechanisms of this antagonistic cross-talk have been elusive. We discuss new findings that illuminate how H3-K4 and H3-K36 methylation, H3-K27 acetylation, and H3-S28 phosphorylation each exert a negative impact on PRC2 function. The emerging picture presents PRC2 as a cooperative multipart machine, intricately outfitted to sense and respond to the local chromatin environment and other cues. This PRC2 design ensures flexibility and fine tuning of its fundamental gene silencing roles in diverse biological contexts.
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Stepanik VA, Harte PJ. A mutation in the E(Z) methyltransferase that increases trimethylation of histone H3 lysine 27 and causes inappropriate silencing of active Polycomb target genes. Dev Biol 2011; 364:249-58. [PMID: 22182520 DOI: 10.1016/j.ydbio.2011.12.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 11/12/2011] [Accepted: 12/01/2011] [Indexed: 01/08/2023]
Abstract
Drosophila Polycomb Repressive Complex 2 (PRC2) is a lysine methyltransferase that trimethylates histone H3 lysine 27 (H3K27me3), a modification essential for Polycomb silencing. Mutations in its catalytic subunit, E(Z), that abolish its methyltransferase activity disrupt Polycomb silencing, causing derepression of Polycomb target genes in cells where they are normally silenced. In contrast, the unusual E(z) mutant allele Trithorax mimic (E(z)(Trm)) causes dominant homeotic phenotypes similar to those caused by mutations in trithorax (trx), an antagonist of Polycomb silencing. This suggests that E(z)(Trm) causes inappropriate silencing of Polycomb target genes in cells where they are normally active. Here we show that E(z)(Trm) mutants have an elevated level of H3K27me3 and reduced levels of H3K27me1 and H3K27me2, modifications also carried out by E(Z). This suggests that the E(z)(Trm) mutation increases the H3K27 trimethylation efficiency of E(Z). Acetylated H3K27 (H3K27ac), a mark of transcriptionally active genes that directly antagonizes H3K27 methylation by E(Z), is also reduced in E(z)(Trm) mutants, consistent with their elevated H3K27me3 level causing inappropriate silencing. In 0-4h E(z)(Trm) embryos, H3K27me3 accumulates prematurely and to high levels and does so at the expense of H3K27ac, which is normally present at high levels in early embryos. Despite their high level of H3K27me3, expression of Abd-B initiates normally in homozygous E(z)(Trm) embryos, but is substantially lower than in wild type embryos by completion of germ band retraction. These results suggest that increased H3K27 trimethylation activity of E(Z)(Trm) causes the premature accumulation of H3K27me3 in early embryogenesis, "predestining" initially active Polycomb target genes to silencing once Polycomb silencing is initiated.
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Affiliation(s)
- Vincent A Stepanik
- Department of Genetics, Case Western Reserve University, Cleveland, OH, USA.
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Histone methylation by PRC2 is inhibited by active chromatin marks. Mol Cell 2011; 42:330-41. [PMID: 21549310 DOI: 10.1016/j.molcel.2011.03.025] [Citation(s) in RCA: 524] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 12/08/2010] [Accepted: 03/18/2011] [Indexed: 02/01/2023]
Abstract
The Polycomb repressive complex 2 (PRC2) confers transcriptional repression through histone H3 lysine 27 trimethylation (H3K27me3). Here, we examined how PRC2 is modulated by histone modifications associated with transcriptionally active chromatin. We provide the molecular basis of histone H3 N terminus recognition by the PRC2 Nurf55-Su(z)12 submodule. Binding of H3 is lost if lysine 4 in H3 is trimethylated. We find that H3K4me3 inhibits PRC2 activity in an allosteric fashion assisted by the Su(z)12 C terminus. In addition to H3K4me3, PRC2 is inhibited by H3K36me2/3 (i.e., both H3K36me2 and H3K36me3). Direct PRC2 inhibition by H3K4me3 and H3K36me2/3 active marks is conserved in humans, mouse, and fly, rendering transcriptionally active chromatin refractory to PRC2 H3K27 trimethylation. While inhibition is present in plant PRC2, it can be modulated through exchange of the Su(z)12 subunit. Inhibition by active chromatin marks, coupled to stimulation by transcriptionally repressive H3K27me3, enables PRC2 to autonomously template repressive H3K27me3 without overwriting active chromatin domains.
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