201
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Chen DH, Huang Y, Ruan Y, Shen WH. The evolutionary landscape of PRC1 core components in green lineage. PLANTA 2016; 243:825-46. [PMID: 26729480 DOI: 10.1007/s00425-015-2451-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 12/16/2015] [Indexed: 05/20/2023]
Abstract
The origin and evolution of plant PRC1 core components. Polycomb repressive complex1 (PRC1) plays critical roles in epigenetic silencing of homeotic genes and determination of cell fate. Animal PRC1 has been well investigated for a long time, whereas plant PRC1 was just confirmed in recent years. It is enigmatic whether PRC1 core components in plants share a common ancestor with those in animals. We evaluated the origin of plant PRC1 RING-finger proteins (RING1 and BMI1) through comparing with the homologs in some representative unikonts and using BMI1- and RING1-like proteins as reciprocal outgroup, finding both PRC1 RING-finger proteins have the earliest origin in mosses, similar to LHP1. Additionally, the gene structure, copy number, and domain organization were analyzed to deeply understand the evolutionary history of plant PRC1 complex. In conclusion, PRC1 RING-finger proteins have independent origins in plants and animals, but convergent evolution might attribute to the conservation of PRC1 complex in plants and animals. Plant LHP1 as the homolog of non-PRC1 protein HP1 was recruited to fulfill the role of Pc counterpart. Gene duplication followed by functional divergence makes a great contribution to evolutionary progress of PRC1 in green plants.
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Affiliation(s)
- Dong-hong Chen
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, Hunan Agricultural University, 410128, Changsha, China.
| | - Yong Huang
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, Hunan Agricultural University, 410128, Changsha, China
| | - Ying Ruan
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, Hunan Agricultural University, 410128, Changsha, China.
| | - Wen-Hui Shen
- College of Bioscience and Biotechnology, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, Hunan Agricultural University, 410128, Changsha, China
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, 12 rue du Général Zimmer, 67084, Strasbourg Cedex, France
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202
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A positive role for polycomb in transcriptional regulation via H4K20me1. Cell Res 2016; 26:529-42. [PMID: 27002220 PMCID: PMC4856762 DOI: 10.1038/cr.2016.33] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 02/03/2016] [Accepted: 02/04/2016] [Indexed: 12/24/2022] Open
Abstract
The highly conserved polycomb group (PcG) proteins maintain heritable transcription repression of the genes essential for development from fly to mammals. However, sporadic reports imply a potential role of PcGs in positive regulation of gene transcription, although systematic investigation of such function and the underlying mechanism has rarely been reported. Here, we report a Pc-mediated, H3K27me3-dependent positive transcriptional regulation of Senseless (Sens), a key transcription factor required for development. Mechanistic studies show that Pc regulates Sens expression by promoting H4K20me1 at the Sens locus. Further bioinformatic analysis at genome-wide level indicates that the existence of H4K20me1 acts as a selective mark for positive transcriptional regulation by Pc/H3K27me3. Both the intensities and specific patterns of Pc and H3K27me3 are important for the fates of target gene transcription. Moreover, binding of transcription factor Broad (Br), which physically interacts with Pc and positively regulates the transcription of Sens, is observed in Pc+H3K27me3+H4K20me1+ genes, but not in Pc+H3K27me3+H4K20me1− genes. Taken together, our study reveals that, coupling with the transcription factor Br, Pc positively regulates transcription of Pc+H3K27me3+H4K20me1+ genes in developing Drosophila wing disc.
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203
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Feinberg AP, Koldobskiy MA, Göndör A. Epigenetic modulators, modifiers and mediators in cancer aetiology and progression. Nat Rev Genet 2016; 17:284-99. [PMID: 26972587 DOI: 10.1038/nrg.2016.13] [Citation(s) in RCA: 575] [Impact Index Per Article: 71.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This year is the tenth anniversary of the publication in this journal of a model suggesting the existence of 'tumour progenitor genes'. These genes are epigenetically disrupted at the earliest stages of malignancies, even before mutations, and thus cause altered differentiation throughout tumour evolution. The past decade of discovery in cancer epigenetics has revealed a number of similarities between cancer genes and stem cell reprogramming genes, widespread mutations in epigenetic regulators, and the part played by chromatin structure in cellular plasticity in both development and cancer. In the light of these discoveries, we suggest here a framework for cancer epigenetics involving three types of genes: 'epigenetic mediators', corresponding to the tumour progenitor genes suggested earlier; 'epigenetic modifiers' of the mediators, which are frequently mutated in cancer; and 'epigenetic modulators' upstream of the modifiers, which are responsive to changes in the cellular environment and often linked to the nuclear architecture. We suggest that this classification is helpful in framing new diagnostic and therapeutic approaches to cancer.
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Affiliation(s)
- Andrew P Feinberg
- Center for Epigenetics, Johns Hopkins University School of Medicine, 855 N. Wolfe Street, Rangos 570, Baltimore, Maryland 21205, USA
| | - Michael A Koldobskiy
- Center for Epigenetics, Johns Hopkins University School of Medicine, 855 N. Wolfe Street, Rangos 570, Baltimore, Maryland 21205, USA
| | - Anita Göndör
- Department of Microbiology, Tumour and Cell Biology, Nobels väg 16, Karolinska Institutet, S-171 77 Stockholm, Sweden
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204
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Zhou Y, Wang L, Vaseghi HR, Liu Z, Lu R, Alimohamadi S, Yin C, Fu JD, Wang GG, Liu J, Qian L. Bmi1 Is a Key Epigenetic Barrier to Direct Cardiac Reprogramming. Cell Stem Cell 2016; 18:382-95. [PMID: 26942853 PMCID: PMC4779178 DOI: 10.1016/j.stem.2016.02.003] [Citation(s) in RCA: 162] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 11/01/2015] [Accepted: 02/12/2016] [Indexed: 02/08/2023]
Abstract
Direct reprogramming of induced cardiomyocytes (iCMs) suffers from low efficiency and requires extensive epigenetic repatterning, although the underlying mechanisms are largely unknown. To address these issues, we screened for epigenetic regulators of iCM reprogramming and found that reducing levels of the polycomb complex gene Bmi1 significantly enhanced induction of beating iCMs from neonatal and adult mouse fibroblasts. The inhibitory role of Bmi1 in iCM reprogramming is mediated through direct interactions with regulatory regions of cardiogenic genes, rather than regulation of cell proliferation. Reduced Bmi1 expression corresponded with increased levels of the active histone mark H3K4me3 and reduced levels of repressive H2AK119ub at cardiogenic loci, and de-repression of cardiogenic gene expression during iCM conversion. Furthermore, Bmi1 deletion could substitute for Gata4 during iCM reprogramming. Thus, Bmi1 acts as a critical epigenetic barrier to iCM production. Bypassing this barrier simplifies iCM generation and increases yield, potentially streamlining iCM production for therapeutic purposes.
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Affiliation(s)
- Yang Zhou
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Li Wang
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Haley Ruth Vaseghi
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Ziqing Liu
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Rui Lu
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Sahar Alimohamadi
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Chaoying Yin
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Ji-Dong Fu
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, OH 44109, USA
| | - Greg G Wang
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Jiandong Liu
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Li Qian
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, NC 27599, USA.
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205
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Zou C, Zhang Y, Ouyang Z. HSA: integrating multi-track Hi-C data for genome-scale reconstruction of 3D chromatin structure. Genome Biol 2016; 17:40. [PMID: 26936376 PMCID: PMC4774023 DOI: 10.1186/s13059-016-0896-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 02/10/2016] [Indexed: 11/24/2022] Open
Abstract
Genome-wide 3C technologies (Hi-C) are being increasingly employed to study three-dimensional (3D) genome conformations. Existing computational approaches are unable to integrate accumulating data to facilitate studying 3D chromatin structure and function. We present HSA (http://ouyanglab.jax.org/hsa/), a flexible tool that jointly analyzes multiple contact maps to infer 3D chromatin structure at the genome scale. HSA globally searches the latent structure underlying different cleavage footprints. Its robustness and accuracy outperform or rival existing tools on extensive simulations and orthogonal experiment validations. Applying HSA to recent in situ Hi-C data, we found the 3D chromatin structures are highly conserved across various human cell types.
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Affiliation(s)
- Chenchen Zou
- The Jackson Laboratory for Genomic Medicine, Farmington, 06032, CT, USA.
| | - Yuping Zhang
- Department of Statistics, University of Connecticut, Storrs, 06269, CT, USA. .,Institute for Systems Genomics, University of Connecticut, Farmington, 06030, CT, USA. .,Institute for Collaboration on Health, Intervention, and Policy, University of Connecticut, Storrs, 06269, CT, USA. .,Center for Quantitative Medicine, University of Connecticut, Farmington, 06030, CT, USA. .,The Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, 06269, CT, USA.
| | - Zhengqing Ouyang
- The Jackson Laboratory for Genomic Medicine, Farmington, 06032, CT, USA. .,Institute for Systems Genomics, University of Connecticut, Farmington, 06030, CT, USA. .,Department of Biomedical Engineering, University of Connecticut, Storrs, 06269, CT, USA. .,Department of Genetics and Genome Sciences, University of Connecticut, Farmington, 06030, CT, USA.
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206
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Stuckey JI, Dickson BM, Cheng N, Liu Y, Norris JL, Cholensky SH, Tempel W, Qin S, Huber KG, Sagum C, Black K, Li F, Huang XP, Roth BL, Baughman BM, Senisterra G, Pattenden SG, Vedadi M, Brown PJ, Bedford MT, Min J, Arrowsmith CH, James LI, Frye SV. A cellular chemical probe targeting the chromodomains of Polycomb repressive complex 1. Nat Chem Biol 2016; 12:180-7. [PMID: 26807715 PMCID: PMC4755828 DOI: 10.1038/nchembio.2007] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 11/25/2015] [Indexed: 12/29/2022]
Abstract
We report the design and characterization of UNC3866, a potent antagonist of the methyllysine (Kme) reading function of the Polycomb CBX and CDY families of chromodomains. Polycomb CBX proteins regulate gene expression by targeting Polycomb repressive complex 1 (PRC1) to sites of H3K27me3 via their chromodomains. UNC3866 binds the chromodomains of CBX4 and CBX7 most potently, with a K(d) of ∼100 nM for each, and is 6- to 18-fold selective as compared to seven other CBX and CDY chromodomains while being highly selective over >250 other protein targets. X-ray crystallography revealed that UNC3866's interactions with the CBX chromodomains closely mimic those of the methylated H3 tail. UNC4195, a biotinylated derivative of UNC3866, was used to demonstrate that UNC3866 engages intact PRC1 and that EED incorporation into PRC1 is isoform dependent in PC3 prostate cancer cells. Finally, UNC3866 inhibits PC3 cell proliferation, consistent with the known ability of CBX7 overexpression to confer a growth advantage, whereas UNC4219, a methylated negative control compound, has negligible effects.
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Affiliation(s)
- Jacob I Stuckey
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Bradley M Dickson
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Nancy Cheng
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Yanli Liu
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Jacqueline L Norris
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Stephanie H Cholensky
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Wolfram Tempel
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Su Qin
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Katherine G Huber
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Cari Sagum
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, Texas, USA
| | - Karynne Black
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, Texas, USA
| | - Fengling Li
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Xi-Ping Huang
- National Institute of Mental Health Psychoactive Drug Screening Program, University of North Carolina at Chapel Hill Medical School, Chapel Hill, North Carolina, USA
- Department of Pharmacology, University of North Carolina at Chapel Hill Medical School, Chapel Hill, North Carolina, USA
| | - Bryan L Roth
- National Institute of Mental Health Psychoactive Drug Screening Program, University of North Carolina at Chapel Hill Medical School, Chapel Hill, North Carolina, USA
- Department of Pharmacology, University of North Carolina at Chapel Hill Medical School, Chapel Hill, North Carolina, USA
| | - Brandi M Baughman
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | | | - Samantha G Pattenden
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Masoud Vedadi
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Peter J Brown
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Mark T Bedford
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, Texas, USA
| | - Jinrong Min
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Cheryl H Arrowsmith
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Lindsey I James
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Stephen V Frye
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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207
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The molecular mechanics of mixed lineage leukemia. Oncogene 2016; 35:5215-5223. [PMID: 26923329 DOI: 10.1038/onc.2016.30] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 01/14/2016] [Accepted: 01/21/2016] [Indexed: 12/14/2022]
Abstract
Mixed lineage leukemia caused by MLL fusion proteins is still a mostly incurable disease. Research on novel treatment strategies has gained momentum in the last years with the elucidation of the molecular mechanisms underlying the transforming potential of these powerful oncoproteins. This review summarizes the recent developments in this area including new attempts to treat MLL in a rational way by exploiting the biochemical vulnerabilities of the leukemogenic process.
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208
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Abstract
A recent super-resolution imaging study by Boettiger et al. elegantly demonstrates that three epigenetically defined, and functionally disparate, chromatin states have distinct folding characteristics in Drosophila nuclei.
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209
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Gu Z, Jin K, Crabbe MJC, Zhang Y, Liu X, Huang Y, Hua M, Nan P, Zhang Z, Zhong Y. Enrichment analysis of Alu elements with different spatial chromatin proximity in the human genome. Protein Cell 2016; 7:250-266. [PMID: 26861146 PMCID: PMC4818845 DOI: 10.1007/s13238-015-0240-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 11/24/2015] [Indexed: 02/03/2023] Open
Abstract
Transposable elements (TEs) have no longer been totally considered as “junk DNA” for quite a time since the continual discoveries of their multifunctional roles in eukaryote genomes. As one of the most important and abundant TEs that still active in human genome, Alu, a SINE family, has demonstrated its indispensable regulatory functions at sequence level, but its spatial roles are still unclear. Technologies based on 3C (chromosome conformation capture) have revealed the mysterious three-dimensional structure of chromatin, and make it possible to study the distal chromatin interaction in the genome. To find the role TE playing in distal regulation in human genome, we compiled the new released Hi-C data, TE annotation, histone marker annotations, and the genome-wide methylation data to operate correlation analysis, and found that the density of Alu elements showed a strong positive correlation with the level of chromatin interactions (hESC: r = 0.9, P < 2.2 × 1016; IMR90 fibroblasts: r = 0.94, P < 2.2 × 1016) and also have a significant positive correlation with some remote functional DNA elements like enhancers and promoters (Enhancer: hESC: r = 0.997, P = 2.3 × 10−4; IMR90: r = 0.934, P = 2 × 10−2; Promoter: hESC: r = 0.995, P = 3.8 × 10−4; IMR90: r = 0.996, P = 3.2 × 10−4). Further investigation involving GC content and methylation status showed the GC content of Alu covered sequences shared a similar pattern with that of the overall sequence, suggesting that Alu elements also function as the GC nucleotide and CpG site provider. In all, our results suggest that the Alu elements may act as an alternative parameter to evaluate the Hi-C data, which is confirmed by the correlation analysis of Alu elements and histone markers. Moreover, the GC-rich Alu sequence can bring high GC content and methylation flexibility to the regions with more distal chromatin contact, regulating the transcription of tissue-specific genes.
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Affiliation(s)
- Zhuoya Gu
- School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Ke Jin
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, ON, M5S 1A1, Canada
| | - M James C Crabbe
- Department of Zoology, University of Oxford, Tinbergen Building, South Parks Road, Oxford, OX1 3PS, UK
- Institute of Biomedical and Environmental Science & Technology, Department of Life Sciences, University of Bedfordshire, Park Square, Luton, LU1 3JU, UK
| | - Yang Zhang
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Champaign, IL, 61801, USA
| | - Xiaolin Liu
- School of Public Health, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Yanyan Huang
- School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Mengyi Hua
- School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Peng Nan
- School of Life Sciences, Fudan University, Shanghai, 200433, China.
| | - Zhaolei Zhang
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, ON, M5S 1A1, Canada.
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 1A1, Canada.
| | - Yang Zhong
- School of Life Sciences, Fudan University, Shanghai, 200433, China.
- Institute of Biodiversity Science and Institute of High Altitude Medicine, Tibet University, Lhasa, 850012, China.
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210
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Abstract
The role of genome architecture in transcription regulation has become the focus of an increasing number of studies over the past decade. Chromatin organization can have a significant impact on gene expression by promoting or restricting the physical proximity between regulatory DNA elements. Given that any change in chromatin state has the potential to alter DNA folding and the proximity between control elements, the spatial organization of chromatin is inherently linked to its molecular composition. In this review, we explore how modulators of chromatin state and organization might keep gene expression in check. We discuss recent findings and present some of the less well-studied aspects of spatial genome organization such as chromatin dynamics and regulation by non-coding RNAs.
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211
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Polycomb inhibits histone acetylation by CBP by binding directly to its catalytic domain. Proc Natl Acad Sci U S A 2016; 113:E744-53. [PMID: 26802126 DOI: 10.1073/pnas.1515465113] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Drosophila Polycomb (PC), a subunit of Polycomb repressive complex 1 (PRC1), is well known for its role in maintaining repression of the homeotic genes and many others and for its binding to trimethylated histone H3 on Lys 27 (H3K27me3) via its chromodomain. Here, we identify a novel activity of PC: inhibition of the histone acetylation activity of CREB-binding protein (CBP). We show that PC and its mammalian CBX orthologs interact directly with the histone acetyltransferase (HAT) domain of CBP, binding to the previously identified autoregulatory loop, whose autoacetylation greatly enhances HAT activity. We identify a conserved PC motif adjacent to the chromodomain required for CBP binding and show that PC binding inhibits acetylation of histone H3. CBP autoacetylation impairs PC binding in vitro, and PC is preferentially associated with unacetylated CBP in vivo. PC knockdown elevates the acetylated H3K27 (H3K27ac) level globally and at promoter regions of some genes that are bound by both PC and CBP. Conversely, PC overexpression decreases the H3K27ac level in vivo and also suppresses CBP-dependent Polycomb phenotypes caused by overexpression of Trithorax, an antagonist of Polycomb silencing. We find that PC is physically associated with the initiating form of RNA polymerase II (Pol II) and that many promoters co-occupied by PC and CBP are associated with paused Pol II, suggesting that PC may play a role in Pol II pausing. These results suggest that PC/PRC1 inhibition of CBP HAT activity plays a role in regulating transcription of both repressed and active PC-regulated genes.
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212
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H2A.Z.1 Monoubiquitylation Antagonizes BRD2 to Maintain Poised Chromatin in ESCs. Cell Rep 2016; 14:1142-1155. [PMID: 26804911 DOI: 10.1016/j.celrep.2015.12.100] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 10/16/2015] [Accepted: 12/22/2015] [Indexed: 12/13/2022] Open
Abstract
Histone variant H2A.Z occupies the promoters of active and poised, bivalent genes in embryonic stem cells (ESCs) to regulate developmental programs, yet how it contributes to these contrasting states is poorly understood. Here, we investigate the function of H2A.Z.1 monoubiquitylation (H2A.Z.1ub) by mutation of the PRC1 target residues (H2A.Z.1(K3R3)). We show that H2A.Z.1(K3R3) is properly incorporated at target promoters in murine ESCs (mESCs), but loss of monoubiquitylation leads to de-repression of bivalent genes, loss of Polycomb binding, and faulty lineage commitment. Using quantitative proteomics, we find that tandem bromodomain proteins, including the BET family member BRD2, are enriched in H2A.Z.1 chromatin. We further show that BRD2 is gained at de-repressed promoters in H2A.Z.1(K3R3) mESCs, whereas BRD2 inhibition restores gene silencing at these sites. Together, our study reveals an antagonistic relationship between H2A.Z.1ub and BRD2 to regulate the transcriptional balance at bivalent genes to enable proper execution of developmental programs.
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213
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Visualizing the HoxD Gene Cluster at the Nanoscale Level. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2016; 80:9-16. [PMID: 26767994 DOI: 10.1101/sqb.2015.80.027177] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Transcription of HoxD cluster genes in limbs is coordinated by two topologically associating domains (TADs), neighboring the cluster and containing various enhancers. Here, we use a combination of microscopy approaches and chromosome conformation capture to assess the structural changes occurring in this global architecture in various functional states. We observed that despite their spatial juxtaposition, the TADs are consistently kept as distinct three-dimensional units. Hox genes located at their boundary can show significant spatial segregation over long distances, suggesting that physical elongation of the HoxD cluster occurs. The use of superresolution imaging (STORM [stochastic optical reconstruction microscopy]) revealed that the gene cluster can be in an either compact or elongated shape. The latter configuration is observed in transcriptionally active tissue and in embryonic stem cells, consistent with chromosome conformation capture results. Such morphological changes at HoxD in developing digits seem to be associated with its position at the boundary between two TADs and support the idea that chromatin dynamics is important in the establishment of transcriptional activity.
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214
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Minarovits J, Banati F, Szenthe K, Niller HH. Epigenetic Regulation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 879:1-25. [DOI: 10.1007/978-3-319-24738-0_1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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215
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Role of Polycomb RYBP in Maintaining the B-1-to-B-2 B-Cell Lineage Switch in Adult Hematopoiesis. Mol Cell Biol 2015; 36:900-12. [PMID: 26711264 DOI: 10.1128/mcb.00869-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 12/18/2015] [Indexed: 01/01/2023] Open
Abstract
Polycomb chromatin modifiers regulate hematopoietic pluripotent stem and progenitor cell self-renewal and expansion. Polycomb complex redundancy and biochemical heterogeneity complicate the unraveling of the functional contributions of distinct components. We have studied the hematopoietic activity of RYBP, a direct interactor and proposed modulator of RING1A/RING1B-dependent histone H2A monoubiquitylation (H2AUb). Using a mouse model to conditionally inactivate Rybp in adult hematopoiesis, we have found that RYBP deletion results in a reversion of B-1-to-B-2 B-cell progenitor ratios, i.e., of the innate (predominantly fetal) to acquired (mostly adult) immunity precursors. Increased numbers of B-1 progenitors correlated with a loss of pre-proB cells, the B-2 progenitors. RYBP-deficient stem and progenitor cell populations (LKS) and isolated common lymphoid progenitors (CLP) gave rise to increased numbers of B-1 progenitors in vitro. Rybp inactivation, however, did not result in changes of global H2AUb and did not interact genetically with Ring1A or Ring1B deletions. These results show that a sustained regulation of the B-1-to-B-2 switch is needed throughout adult life and that RYBP plays an important role in keeping B-2 dominance, most likely independently of its Polycomb affiliation.
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216
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Illingworth RS, Moffat M, Mann AR, Read D, Hunter CJ, Pradeepa MM, Adams IR, Bickmore WA. The E3 ubiquitin ligase activity of RING1B is not essential for early mouse development. Genes Dev 2015; 29:1897-902. [PMID: 26385961 PMCID: PMC4579347 DOI: 10.1101/gad.268151.115] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Polycomb-repressive complex 1 (PRC1) and PRC2 maintain repression at many developmental genes in mouse embryonic stem cells and are required for early development. However, it is still unclear how they are targeted and how they function. We show that the ability of RING1B, a core component of PRC1, to ubiquitinate histone H2A is dispensable for early mouse embryonic development and much of the gene repression activity of PRC1. Our data support a model in which PRC1 and PRC2 reinforce each other's binding but suggest that the key functions of PRC1 lie beyond the enzymatic capabilities of RING1B.
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Affiliation(s)
- Robert S Illingworth
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - Michael Moffat
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - Abigail R Mann
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - David Read
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - Chris J Hunter
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - Madapura M Pradeepa
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - Ian R Adams
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
| | - Wendy A Bickmore
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH42XU, United Kingdom
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217
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Abstract
Our knowledge of the variety and abundances of RNA base modifications is rapidly increasing. Modified bases have critical roles in tRNAs, rRNAs, translation, splicing, RNA interference, and other RNA processes, and are now increasingly detected in all types of transcripts. Can new biological principles associated with this diversity of RNA modifications, particularly in mRNAs and long non-coding RNAs, be identified? This review will explore this question by focusing primarily on adenosine to inosine (A-to-I) RNA editing by the adenine deaminase acting on RNA (ADAR) enzymes that have been intensively studied for the past 20 years and have a wide range of effects. Over 100 million adenosine to inosine editing sites have been identified in the human transcriptome, mostly in embedded Alu sequences that form potentially innate immune-stimulating dsRNA hairpins in transcripts. Recent research has demonstrated that inosine in the epitranscriptome and ADAR1 protein establish innate immune tolerance for host dsRNA formed by endogenous sequences. Innate immune sensors that detect viral nucleic acids are among the readers of epitranscriptome RNA modifications, though this does preclude a wide range of other modification effects.
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Affiliation(s)
- Mary A. O’Connell
- CEITEC Masaryk University, Brno, Czech Republic
- * E-mail: (MAO); (LPK)
| | - Niamh M. Mannion
- Paul O’Gorman Leukaemia Research Centre, Institute of Cancer Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Liam P. Keegan
- CEITEC Masaryk University, Brno, Czech Republic
- * E-mail: (MAO); (LPK)
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218
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Kataoka K, Mochizuki K. Phosphorylation of an HP1-like Protein Regulates Heterochromatin Body Assembly for DNA Elimination. Dev Cell 2015; 35:775-88. [PMID: 26688337 PMCID: PMC4695338 DOI: 10.1016/j.devcel.2015.11.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 08/29/2015] [Accepted: 11/17/2015] [Indexed: 01/06/2023]
Abstract
Heterochromatic loci are often assembled into higher-order heterochromatin bodies in diverse eukaryotes. However, the formation and biological roles of heterochromatin bodies are poorly understood. In the ciliated protozoan Tetrahymena, de novo heterochromatin body formation is accompanied by programmed DNA elimination. Here, we show that the heterochromatin body component Jub1p promotes heterochromatin body formation and dephosphorylation of the Heterochromatin Protein 1-like protein Pdd1p. Through the mutagenesis of the phosphorylated residues of Pdd1p, we demonstrate that Pdd1p dephosphorylation promotes the electrostatic interaction between Pdd1p and RNA in vitro and heterochromatin body formation in vivo. We therefore propose that heterochromatin body is assembled by the Pdd1p-RNA interaction. Pdd1p dephosphorylation and Jub1p are required for heterochromatin body formation and DNA elimination but not for local heterochromatin assembly, indicating that heterochromatin body plays an essential role in DNA elimination.
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Affiliation(s)
- Kensuke Kataoka
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Kazufumi Mochizuki
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Dr. Bohr-Gasse 3, 1030 Vienna, Austria.
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219
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Liang SC, Hartwig B, Perera P, Mora-García S, de Leau E, Thornton H, de Alves FL, Rapsilber J, Yang S, James GV, Schneeberger K, Finnegan EJ, Turck F, Goodrich J. Kicking against the PRCs - A Domesticated Transposase Antagonises Silencing Mediated by Polycomb Group Proteins and Is an Accessory Component of Polycomb Repressive Complex 2. PLoS Genet 2015; 11:e1005660. [PMID: 26642436 PMCID: PMC4671723 DOI: 10.1371/journal.pgen.1005660] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 10/20/2015] [Indexed: 11/18/2022] Open
Abstract
The Polycomb group (PcG) and trithorax group (trxG) genes play crucial roles in development by regulating expression of homeotic and other genes controlling cell fate. Both groups catalyse modifications of chromatin, particularly histone methylation, leading to epigenetic changes that affect gene activity. The trxG antagonizes the function of PcG genes by activating PcG target genes, and consequently trxG mutants suppress PcG mutant phenotypes. We previously identified the ANTAGONIST OF LIKE HETEROCHROMATIN PROTEIN1 (ALP1) gene as a genetic suppressor of mutants in the Arabidopsis PcG gene LIKE HETEROCHROMATIN PROTEIN1 (LHP1). Here, we show that ALP1 interacts genetically with several other PcG and trxG components and that it antagonizes PcG silencing. Transcriptional profiling reveals that when PcG activity is compromised numerous target genes are hyper-activated in seedlings and that in most cases this requires ALP1. Furthermore, when PcG activity is present ALP1 is needed for full activation of several floral homeotic genes that are repressed by the PcG. Strikingly, ALP1 does not encode a known chromatin protein but rather a protein related to PIF/Harbinger class transposases. Phylogenetic analysis indicates that ALP1 is broadly conserved in land plants and likely lost transposase activity and acquired a novel function during angiosperm evolution. Consistent with this, immunoprecipitation and mass spectrometry (IP-MS) show that ALP1 associates, in vivo, with core components of POLYCOMB REPRESSIVE COMPLEX 2 (PRC2), a widely conserved PcG protein complex which functions as a H3K27me3 histone methyltransferase. Furthermore, in reciprocal pulldowns using the histone methyltransferase CURLY LEAF (CLF), we identify not only ALP1 and the core PRC2 components but also plant-specific accessory components including EMBRYONIC FLOWER 1 (EMF1), a transcriptional repressor previously associated with PRC1-like complexes. Taken together our data suggest that ALP1 inhibits PcG silencing by blocking the interaction of the core PRC2 with accessory components that promote its HMTase activity or its role in inhibiting transcription. ALP1 is the first example of a domesticated transposase acquiring a novel function as a PcG component. The antagonistic interaction of a modified transposase with the PcG machinery is novel and may have arisen as a means for the cognate transposon to evade host surveillance or for the host to exploit features of the transposition machinery beneficial for epigenetic regulation of gene activity. Transposons are parasitic genetic elements that proliferate within their hosts’ genomes. Because rampant transposition is usually deleterious, hosts have evolved ways to inhibit the activity of transposons. In plants, this genome defence is provided by the Polycomb group (PcG) proteins and/or the DNA methylation machinery, which repress the transcription of transposase genes. We identified the Arabidopsis ALP1 gene through its role in opposing gene silencing mediated by PcG genes. ALP1 is an ancient gene in land plants and has evolved from a domesticated transposase. Unexpectedly, we find that the ALP1 protein is present in a conserved complex of PcG proteins that inhibit transcription by methylating the histone proteins that package DNA. ALP1 likely inhibits the activity of this PcG complex by blocking its interaction with accessory proteins that stimulate its activity. We suggest that the inhibition of the PcG by a transposase may originally have evolved as a means for transposons to evade surveillance by their hosts, and that subsequently hosts may have exploited this as a means to regulate PcG activity. Our work illustrates how transposons can be friend or fiend, and raises the question of whether other transposases will also be found to inhibit their host’s regulatory machinery.
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Affiliation(s)
- Shih Chieh Liang
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Ben Hartwig
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Köln, Germany
| | - Pumi Perera
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Santiago Mora-García
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Erica de Leau
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Harry Thornton
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Flavia Lima de Alves
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Juri Rapsilber
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Suxin Yang
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Geo Velikkakam James
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Köln, Germany
| | - Korbinian Schneeberger
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Köln, Germany
| | | | - Franziska Turck
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Köln, Germany
- * E-mail: (FT); (JG)
| | - Justin Goodrich
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (FT); (JG)
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220
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Aranda S, Mas G, Di Croce L. Regulation of gene transcription by Polycomb proteins. SCIENCE ADVANCES 2015; 1:e1500737. [PMID: 26665172 PMCID: PMC4672759 DOI: 10.1126/sciadv.1500737] [Citation(s) in RCA: 237] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 09/17/2015] [Indexed: 05/14/2023]
Abstract
The Polycomb group (PcG) of proteins defines a subset of factors that physically associate and function to maintain the positional identity of cells from the embryo to adult stages. PcG has long been considered a paradigmatic model for epigenetic maintenance of gene transcription programs. Despite intensive research efforts to unveil the molecular mechanisms of action of PcG proteins, several fundamental questions remain unresolved: How many different PcG complexes exist in mammalian cells? How are PcG complexes targeted to specific loci? How does PcG regulate transcription? In this review, we discuss the diversity of PcG complexes in mammalian cells, examine newly identified modes of recruitment to chromatin, and highlight the latest insights into the molecular mechanisms underlying the function of PcGs in transcription regulation and three-dimensional chromatin conformation.
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Affiliation(s)
- Sergi Aranda
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain
- Universitat Pompeu Fabra (UPF), Barcelona 08002, Spain
| | - Gloria Mas
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain
- Universitat Pompeu Fabra (UPF), Barcelona 08002, Spain
| | - Luciano Di Croce
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain
- Universitat Pompeu Fabra (UPF), Barcelona 08002, Spain
- Institucio Catalana de Recerca i Estudis Avançats, Pg Lluis Companys 23, Barcelona 08010, Spain
- Corresponding author. E-mail:
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221
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Kim JM, Kim K, Punj V, Liang G, Ulmer TS, Lu W, An W. Linker histone H1.2 establishes chromatin compaction and gene silencing through recognition of H3K27me3. Sci Rep 2015; 5:16714. [PMID: 26581166 PMCID: PMC4652225 DOI: 10.1038/srep16714] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 10/19/2015] [Indexed: 12/21/2022] Open
Abstract
Linker histone H1 is a protein component of chromatin and has been linked to higher-order chromatin compaction and global gene silencing. However, a growing body of evidence suggests that H1 plays a gene-specific role, regulating a relatively small number of genes. Here we show that H1.2, one of the H1 subtypes, is overexpressed in cancer cells and contributes to gene silencing. H1.2 gets recruited to distinct chromatin regions in a manner dependent on EZH2-mediated H3K27me3, and inhibits transcription of multiple growth suppressive genes via modulation of chromatin architecture. The C-terminal tail of H1.2 is critical for the observed effects, because mutations of three H1.2-specific amino acids in this domain abrogate the ability of H1.2 to bind H3K27me3 nucleosomes and inactivate target genes. Collectively, these results provide a molecular explanation for H1.2 functions in the regulation of chromatin folding and indicate that H3K27me3 is a key mechanism governing the recruitment and activity of H1.2 at target loci.
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Affiliation(s)
- Jin-Man Kim
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA 90033, USA.,Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033, USA
| | - Kyunghwan Kim
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA 90033, USA.,Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033, USA.,Department of Biology, College of Natural Sciences, Chungbuk National University, Cheongju, Chungbuk 361-763, Republic of Korea
| | - Vasu Punj
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033, USA.,Department of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Gangning Liang
- Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Tobias S Ulmer
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA 90033, USA.,Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Wange Lu
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA 90033, USA.,Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, University of Southern California, Los Angeles, CA 90033, USA
| | - Woojin An
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA 90033, USA.,Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033, USA
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222
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Martins NMC, Bergmann JH, Shono N, Kimura H, Larionov V, Masumoto H, Earnshaw WC. Epigenetic engineering shows that a human centromere resists silencing mediated by H3K27me3/K9me3. Mol Biol Cell 2015; 27:177-96. [PMID: 26564795 PMCID: PMC4694756 DOI: 10.1091/mbc.e15-08-0605] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 11/03/2015] [Indexed: 12/14/2022] Open
Abstract
Centromeres are embedded within heterochromatin but are transcriptionally active. Centromeric transcription and the centromere function of a human artificial chromosome resist repression mediated by nucleation of repressive marks H3K27me3 or H3K9me3 via tethering of EZH2 or the SET domain of Suv39h1, respectively. Centromeres are characterized by the centromere-specific H3 variant CENP-A, which is embedded in chromatin with a pattern characteristic of active transcription that is required for centromere identity. It is unclear how centromeres remain transcriptionally active despite being flanked by repressive pericentric heterochromatin. To further understand centrochromatin’s response to repressive signals, we nucleated a Polycomb-like chromatin state within the centromere of a human artificial chromosome (HAC) by tethering the methyltransferase EZH2. This led to deposition of the H3K27me3 mark and PRC1 repressor binding. Surprisingly, this state did not abolish HAC centromere function or transcription, and this apparent resistance was not observed on a noncentromeric locus, where transcription was silenced. Directly tethering the reader/repressor PRC1 bypassed this resistance, inactivating the centromere. We observed analogous responses when tethering the heterochromatin Editor Suv39h1-methyltransferase domain (centromere resistance) or reader HP1α (centromere inactivation), respectively. Our results reveal that the HAC centromere can resist repressive pathways driven by H3K9me3/H3K27me3 and may help to explain how centromeres are able to resist inactivation by flanking heterochromatin.
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Affiliation(s)
- Nuno M C Martins
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland, United Kingdom
| | - Jan H Bergmann
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland, United Kingdom
| | - Nobuaki Shono
- Laboratory of Cell Engineering, Department of Frontier Research, Kazusa DNA Research Institute, Kisarazu 292-0818, Japan Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Hiroshi Kimura
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Vladimir Larionov
- Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Hiroshi Masumoto
- Laboratory of Cell Engineering, Department of Frontier Research, Kazusa DNA Research Institute, Kisarazu 292-0818, Japan
| | - William C Earnshaw
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland, United Kingdom
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223
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Blackledge NP, Rose NR, Klose RJ. Targeting Polycomb systems to regulate gene expression: modifications to a complex story. Nat Rev Mol Cell Biol 2015; 16:643-649. [PMID: 26420232 DOI: 10.1038/nrm4067.targeting] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Polycomb group proteins are transcriptional repressors that are essential for normal gene regulation during development. Recent studies suggest that Polycomb repressive complexes (PRCs) recognize and are recruited to their genomic target sites through a range of different mechanisms, which involve transcription factors, CpG island elements and non-coding RNAs. Together with the realization that the interplay between PRC1 and PRC2 is more intricate than was previously appreciated, this has increased our understanding of the vertebrate Polycomb system at the molecular level.
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Affiliation(s)
- Neil P Blackledge
- Department of Biochemistry, South Parks Road, University of Oxford, OX1 3QU
| | - Nathan R Rose
- Department of Biochemistry, South Parks Road, University of Oxford, OX1 3QU
| | - Robert J Klose
- Department of Biochemistry, South Parks Road, University of Oxford, OX1 3QU
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224
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Nanoscale spatial organization of the HoxD gene cluster in distinct transcriptional states. Proc Natl Acad Sci U S A 2015; 112:13964-9. [PMID: 26504220 DOI: 10.1073/pnas.1517972112] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Chromatin condensation plays an important role in the regulation of gene expression. Recently, it was shown that the transcriptional activation of Hoxd genes during vertebrate digit development involves modifications in 3D interactions within and around the HoxD gene cluster. This reorganization follows a global transition from one set of regulatory contacts to another, between two topologically associating domains (TADs) located on either side of the HoxD locus. Here, we use 3D DNA FISH to assess the spatial organization of chromatin at and around the HoxD gene cluster and report that although the two TADs are tightly associated, they appear as spatially distinct units. We measured the relative position of genes within the cluster and found that they segregate over long distances, suggesting that a physical elongation of the HoxD cluster can occur. We analyzed this possibility by super-resolution imaging (STORM) and found that tissues with distinct transcriptional activity exhibit differing degrees of elongation. We also observed that the morphological change of the HoxD cluster in developing digits is associated with its position at the boundary between the two TADs. Such variations in the fine-scale architecture of the gene cluster suggest causal links among its spatial configuration, transcriptional activation, and the flanking chromatin context.
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225
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Xist imprinting is promoted by the hemizygous (unpaired) state in the male germ line. Proc Natl Acad Sci U S A 2015; 112:14415-22. [PMID: 26489649 DOI: 10.1073/pnas.1519528112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The long noncoding X-inactivation-specific transcript (Xist gene) is responsible for mammalian X-chromosome dosage compensation between the sexes, the process by which one of the two X chromosomes is inactivated in the female soma. Xist is essential for both the random and imprinted forms of X-chromosome inactivation. In the imprinted form, Xist is paternally marked to be expressed in female embryos. To investigate the mechanism of Xist imprinting, we introduce Xist transgenes (Tg) into the male germ line. Although ectopic high-level Xist expression on autosomes can be compatible with viability, transgenic animals demonstrate reduced fitness, subfertility, defective meiotic pairing, and other germ-cell abnormalities. In the progeny, paternal-specific expression is recapitulated by the 200-kb Xist Tg. However, Xist imprinting occurs efficiently only when it is in an unpaired or unpartnered state during male meiosis. When transmitted from a hemizygous father (+/Tg), the Xist Tg demonstrates paternal-specific expression in the early embryo. When transmitted by a homozygous father (Tg/Tg), the Tg fails to show imprinted expression. Thus, Xist imprinting is directed by sequences within a 200-kb X-linked region, and the hemizygous (unpaired) state of the Xist region promotes its imprinting in the male germ line.
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226
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Abstract
A wealth of genomic and epigenomic data has identified abnormal regulation of epigenetic processes as a prominent theme in hematologic malignancies. Recurrent somatic alterations in myeloid malignancies of key proteins involved in DNA methylation, post-translational histone modification and chromatin remodeling have highlighted the importance of epigenetic regulation of gene expression in the initiation and maintenance of various malignancies. The rational use of targeted epigenetic therapies requires a thorough understanding of the underlying mechanisms of malignant transformation driven by aberrant epigenetic regulators. In this review we provide an overview of the major protagonists in epigenetic regulation, their aberrant role in myeloid malignancies, prognostic significance and potential for therapeutic targeting.
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Affiliation(s)
- Chun Yew Fong
- Cancer Epigenetics Laboratory, Peter MacCallum Cancer Centre, East Melbourne; The Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Australia
| | - Jessica Morison
- Cancer Epigenetics Laboratory, Peter MacCallum Cancer Centre, East Melbourne
| | - Mark A Dawson
- Cancer Epigenetics Laboratory, Peter MacCallum Cancer Centre, East Melbourne; The Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Australia
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227
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Fukuda A, Mitani A, Miyashita T, Umezawa A, Akutsu H. Chromatin condensation of Xist genomic loci during oogenesis in mice. Development 2015; 142:4049-55. [PMID: 26459223 PMCID: PMC4712840 DOI: 10.1242/dev.127308] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/02/2015] [Indexed: 01/29/2023]
Abstract
Repression of maternal Xist (Xm-Xist) during preimplantation in mouse embryos is essential for establishing imprinted X chromosome inactivation. Nuclear transplantation (NT) studies using nuclei derived from non-growing (ng) and full-grown (fg) oocytes have indicated that maternal-specific repressive modifications are imposed on Xm-Xist during oogenesis, as well as on autosomal imprinted genes. Recent studies have revealed that histone H3 lysine 9 trimethylation (H3K9me3) enrichments on Xm-Xist promoter regions are involved in silencing at the preimplantation stages. However, whether H3K9me3 is imposed on Xm-Xist during oogenesis is not known. Here, we dissected the chromatin states in ng and fg oocytes and early preimplantation stage embryos. Chromatin immunoprecipitation experiments against H3K9me3 revealed that there was no significant enrichment within the Xm-Xist region during oogenesis. However, NT embryos with ng nuclei (ngNT) showed extensive Xm-Xist derepression and H3K9me3 hypomethylation of the promoter region at the 4-cell stage, which corresponds to the onset of paternal Xist expression. We also found that the chromatin state at the Xist genomic locus became markedly condensed as oocyte growth proceeded. Although the condensed Xm-Xist genomic locus relaxed during early preimplantation phases, the extent of the relaxation across Xm-Xist loci derived from normally developed oocytes was significantly smaller than those of paternal-Xist and ngNT-Xist genomic loci. Furthermore, Xm-Xist from 2-cell metaphase nuclei became derepressed following NT. We propose that chromatin condensation is associated with imprinted Xist repression and that skipping of the condensation step by NT leads to Xist activation during the early preimplantation phase. Summary: The analysis of chromatin state and H3K9me3 levels in mouse oocytes and early embryos provides insights into the dynamics of Xist repression and activation during early development and reprogramming.
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Affiliation(s)
- Atsushi Fukuda
- Center for Regenerative Medicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo 157-8535, Japan
| | - Atsushi Mitani
- Center for Regenerative Medicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo 157-8535, Japan Department of Molecular Genetics, Kitasato University Graduate School of Medical Sciences, 1-15-1 Kitasato, Minami, Sagamihara, Kanagawa 252-0374, Japan
| | - Toshiyuki Miyashita
- Department of Molecular Genetics, Kitasato University Graduate School of Medical Sciences, 1-15-1 Kitasato, Minami, Sagamihara, Kanagawa 252-0374, Japan
| | - Akihiro Umezawa
- Center for Regenerative Medicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo 157-8535, Japan
| | - Hidenori Akutsu
- Center for Regenerative Medicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo 157-8535, Japan Department of Stem Cell Research, Fukushima Medical University, 1 Hikarigaoka, Fukushima City, Fukushima 960-1295, Japan
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228
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The quest for mammalian Polycomb response elements: are we there yet? Chromosoma 2015; 125:471-96. [PMID: 26453572 PMCID: PMC4901126 DOI: 10.1007/s00412-015-0539-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 08/31/2015] [Accepted: 09/02/2015] [Indexed: 12/12/2022]
Abstract
A long-standing mystery in the field of Polycomb and Trithorax regulation is how these proteins, which are highly conserved between flies and mammals, can regulate several hundred equally highly conserved target genes, but recognise these targets via cis-regulatory elements that appear to show no conservation in their DNA sequence. These elements, termed Polycomb/Trithorax response elements (PRE/TREs or PREs), are relatively well characterised in flies, but their mammalian counterparts have proved to be extremely difficult to identify. Recent progress in this endeavour has generated a wealth of data and raised several intriguing questions. Here, we ask why and to what extent mammalian PREs are so different to those of the fly. We review recent advances, evaluate current models and identify open questions in the quest for mammalian PREs.
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229
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Sound of silence: the properties and functions of repressive Lys methyltransferases. Nat Rev Mol Cell Biol 2015. [PMID: 26204160 DOI: 10.1038/nrm4029] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The methylation of histone Lys residues by Lys methyltransferases (KMTs) regulates chromatin organization and either activates or represses gene expression, depending on the residue that is targeted. KMTs are emerging as key components in several cellular processes, and their deregulation is often associated with pathogenesis. Here, we review the current knowledge on the main KMTs that are associated with gene silencing: namely, those responsible for methylating histone H3 Lys 9 (H3K9), H3K27 and H4K20. We discuss their biochemical properties and the various mechanisms by which they are targeted to the chromatin and regulate gene expression, as well as new data on the interplay between them and other chromatin modifiers.
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230
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Rai K, Akdemir KC, Kwong LN, Fiziev P, Wu CJ, Keung EZ, Sharma S, Samant NS, Williams M, Axelrad JB, Shah A, Yang D, Grimm EA, Barton MC, Milton DR, Heffernan TP, Horner JW, Ekmekcioglu S, Lazar AJ, Ernst J, Chin L. Dual Roles of RNF2 in Melanoma Progression. Cancer Discov 2015; 5:1314-27. [PMID: 26450788 DOI: 10.1158/2159-8290.cd-15-0493] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 10/06/2015] [Indexed: 12/28/2022]
Abstract
UNLABELLED Epigenetic regulators have emerged as critical factors governing the biology of cancer. Here, in the context of melanoma, we show that RNF2 is prognostic, exhibiting progression-correlated expression in human melanocytic neoplasms. Through a series of complementary gain-of-function and loss-of-function studies in mouse and human systems, we establish that RNF2 is oncogenic and prometastatic. Mechanistically, RNF2-mediated invasive behavior is dependent on its ability to monoubiquitinate H2AK119 at the promoter of LTBP2, resulting in silencing of this negative regulator of TGFβ signaling. In contrast, RNF2's oncogenic activity does not require its catalytic activity nor does it derive from its canonical gene repression function. Instead, RNF2 drives proliferation through direct transcriptional upregulation of the cell-cycle regulator CCND2. We further show that MEK1-mediated phosphorylation of RNF2 promotes recruitment of activating histone modifiers UTX and p300 to a subset of poised promoters, which activates gene expression. In summary, RNF2 regulates distinct biologic processes in the genesis and progression of melanoma via different molecular mechanisms. SIGNIFICANCE The role of epigenetic regulators in cancer progression is being increasingly appreciated. We show novel roles for RNF2 in melanoma tumorigenesis and metastasis, albeit via different mechanisms. Our findings support the notion that epigenetic regulators, such as RNF2, directly and functionally control powerful gene networks that are vital in multiple cancer processes.
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Affiliation(s)
- Kunal Rai
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas.
| | - Kadir C Akdemir
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Lawrence N Kwong
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Petko Fiziev
- Bioinformatics Interdepartmental Program, University of California, Los Angeles, Los Angeles, California. Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, Los Angeles, California. Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, California
| | - Chang-Jiun Wu
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Emily Z Keung
- Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas. Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts
| | - Sneha Sharma
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Neha S Samant
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Maura Williams
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Jacob B Axelrad
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Amiksha Shah
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Dong Yang
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Elizabeth A Grimm
- Department of Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Michelle C Barton
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Denai R Milton
- Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Timothy P Heffernan
- Institute for Applied Cancer Science, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - James W Horner
- Institute for Applied Cancer Science, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Suhendan Ekmekcioglu
- Department of Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Alexander J Lazar
- Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Jason Ernst
- Bioinformatics Interdepartmental Program, University of California, Los Angeles, Los Angeles, California. Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, Los Angeles, California. Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, California. Departments of Biological Chemistry and Computer Science, University of California, Los Angeles, Los Angeles, California. Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California
| | - Lynda Chin
- Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas. Institute for Applied Cancer Science, The University of Texas MD Anderson Cancer Center, Houston, Texas. Institute for Health Transformation, The University of Texas System, Houston, Texas.
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231
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Schoenfelder S, Sugar R, Dimond A, Javierre BM, Armstrong H, Mifsud B, Dimitrova E, Matheson L, Tavares-Cadete F, Furlan-Magaril M, Segonds-Pichon A, Jurkowski W, Wingett SW, Tabbada K, Andrews S, Herman B, LeProust E, Osborne CS, Koseki H, Fraser P, Luscombe NM, Elderkin S. Polycomb repressive complex PRC1 spatially constrains the mouse embryonic stem cell genome. Nat Genet 2015; 47:1179-1186. [PMID: 26323060 PMCID: PMC4847639 DOI: 10.1038/ng.3393] [Citation(s) in RCA: 265] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 08/05/2015] [Indexed: 02/08/2023]
Abstract
The Polycomb repressive complexes PRC1 and PRC2 maintain embryonic stem cell (ESC) pluripotency by silencing lineage-specifying developmental regulator genes. Emerging evidence suggests that Polycomb complexes act through controlling spatial genome organization. We show that PRC1 functions as a master regulator of mouse ESC genome architecture by organizing genes in three-dimensional interaction networks. The strongest spatial network is composed of the four Hox gene clusters and early developmental transcription factor genes, the majority of which contact poised enhancers. Removal of Polycomb repression leads to disruption of promoter-promoter contacts in the Hox gene network. In contrast, promoter-enhancer contacts are maintained in the absence of Polycomb repression, with accompanying widespread acquisition of active chromatin signatures at network enhancers and pronounced transcriptional upregulation of network genes. Thus, PRC1 physically constrains developmental transcription factor genes and their enhancers in a silenced but poised spatial network. We propose that the selective release of genes from this spatial network underlies cell fate specification during early embryonic development.
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Affiliation(s)
| | - Robert Sugar
- EMBL European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK
| | - Andrew Dimond
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | | | - Harry Armstrong
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | - Borbala Mifsud
- Cancer Research UK London Research Institute, London, UK
- Department of Genetics, Evolution & Environment, University College London, London, UK
| | - Emilia Dimitrova
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
- Department of Biochemistry, Oxford University, Oxford, UK
| | - Louise Matheson
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | - Filipe Tavares-Cadete
- Cancer Research UK London Research Institute, London, UK
- present address: Okinawa Institute for Science and Technology Graduate University, Okinawa, Japan
| | | | | | - Wiktor Jurkowski
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | - Steven W Wingett
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
- Bioinformatics, The Babraham Institute, Cambridge, UK
| | - Kristina Tabbada
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | - Simon Andrews
- Bioinformatics, The Babraham Institute, Cambridge, UK
| | - Bram Herman
- Agilent Technologies Inc., Santa Clara, California, USA
| | | | | | - Haruhiko Koseki
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Peter Fraser
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
| | - Nicholas M Luscombe
- EMBL European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK
- Cancer Research UK London Research Institute, London, UK
- Department of Genetics, Evolution & Environment, University College London, London, UK
- Okinawa Institute for Science and Technology Graduate University, Okinawa, Japan
| | - Sarah Elderkin
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, UK
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232
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Targeting Polycomb systems to regulate gene expression: modifications to a complex story. Nat Rev Mol Cell Biol 2015; 16:643-649. [PMID: 26420232 DOI: 10.1038/nrm4067] [Citation(s) in RCA: 250] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Polycomb group proteins are transcriptional repressors that are essential for normal gene regulation during development. Recent studies suggest that Polycomb repressive complexes (PRCs) recognize and are recruited to their genomic target sites through a range of different mechanisms, which involve transcription factors, CpG island elements and non-coding RNAs. Together with the realization that the interplay between PRC1 and PRC2 is more intricate than was previously appreciated, this has increased our understanding of the vertebrate Polycomb system at the molecular level.
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233
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Tatavosian R, Zhen CY, Duc HN, Balas MM, Johnson AM, Ren X. Distinct Cellular Assembly Stoichiometry of Polycomb Complexes on Chromatin Revealed by Single-molecule Chromatin Immunoprecipitation Imaging. J Biol Chem 2015; 290:28038-28054. [PMID: 26381410 DOI: 10.1074/jbc.m115.671115] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Indexed: 12/11/2022] Open
Abstract
Epigenetic complexes play an essential role in regulating chromatin structure, but information about their assembly stoichiometry on chromatin within cells is poorly understood. The cellular assembly stoichiometry is critical for appreciating the initiation, propagation, and maintenance of epigenetic inheritance during normal development and in cancer. By combining genetic engineering, chromatin biochemistry, and single-molecule fluorescence imaging, we developed a novel and sensitive approach termed single-molecule chromatin immunoprecipitation imaging (Sm-ChIPi) to enable investigation of the cellular assembly stoichiometry of epigenetic complexes on chromatin. Sm-ChIPi was validated by using chromatin complexes with known stoichiometry. The stoichiometry of subunits within a polycomb complex and the assembly stoichiometry of polycomb complexes on chromatin have been extensively studied but reached divergent views. Moreover, the cellular assembly stoichiometry of polycomb complexes on chromatin remains unexplored. Using Sm-ChIPi, we demonstrated that within mouse embryonic stem cells, one polycomb repressive complex (PRC) 1 associates with multiple nucleosomes, whereas two PRC2s can bind to a single nucleosome. Furthermore, we obtained direct physical evidence that the nucleoplasmic PRC1 is monomeric, whereas PRC2 can dimerize in the nucleoplasm. We showed that ES cell differentiation induces selective alteration of the assembly stoichiometry of Cbx2 on chromatin but not other PRC1 components. We additionally showed that the PRC2-mediated trimethylation of H3K27 is not required for the assembly stoichiometry of PRC1 on chromatin. Thus, these findings uncover that PRC1 and PRC2 employ distinct mechanisms to assemble on chromatin, and the novel Sm-ChIPi technique could provide single-molecule insight into other epigenetic complexes.
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Affiliation(s)
- Roubina Tatavosian
- Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217-3364
| | - Chao Yu Zhen
- Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217-3364
| | - Huy Nguyen Duc
- Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217-3364
| | - Maggie M Balas
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Aaron M Johnson
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Xiaojun Ren
- Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217-3364.
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234
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Fraser J, Williamson I, Bickmore WA, Dostie J. An Overview of Genome Organization and How We Got There: from FISH to Hi-C. Microbiol Mol Biol Rev 2015; 79:347-72. [PMID: 26223848 PMCID: PMC4517094 DOI: 10.1128/mmbr.00006-15] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In humans, nearly two meters of genomic material must be folded to fit inside each micrometer-scale cell nucleus while remaining accessible for gene transcription, DNA replication, and DNA repair. This fact highlights the need for mechanisms governing genome organization during any activity and to maintain the physical organization of chromosomes at all times. Insight into the functions and three-dimensional structures of genomes comes mostly from the application of visual techniques such as fluorescence in situ hybridization (FISH) and molecular approaches including chromosome conformation capture (3C) technologies. Recent developments in both types of approaches now offer the possibility of exploring the folded state of an entire genome and maybe even the identification of how complex molecular machines govern its shape. In this review, we present key methodologies used to study genome organization and discuss what they reveal about chromosome conformation as it relates to transcription regulation across genomic scales in mammals.
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Affiliation(s)
- James Fraser
- Department of Biochemistry, and Goodman Cancer Research Center, McGill University, Montréal, Québec, Canada
| | - Iain Williamson
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Wendy A Bickmore
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Josée Dostie
- Department of Biochemistry, and Goodman Cancer Research Center, McGill University, Montréal, Québec, Canada
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235
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Rafique S, Thomas JS, Sproul D, Bickmore WA. Estrogen-induced chromatin decondensation and nuclear re-organization linked to regional epigenetic regulation in breast cancer. Genome Biol 2015; 16:145. [PMID: 26235388 PMCID: PMC4536608 DOI: 10.1186/s13059-015-0719-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 07/06/2015] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Epigenetic changes are being increasingly recognized as a prominent feature of cancer. This occurs not only at individual genes, but also over larger chromosomal domains. To investigate this, we set out to identify large chromosomal domains of epigenetic dysregulation in breast cancers. RESULTS We identify large regions of coordinate down-regulation of gene expression, and other regions of coordinate activation, in breast cancers and show that these regions are linked to tumor subtype. In particular we show that a group of coordinately regulated regions are expressed in luminal, estrogen-receptor positive breast tumors and cell lines. For one of these regions of coordinate gene activation, we show that regional epigenetic regulation is accompanied by visible unfolding of large-scale chromatin structure and a repositioning of the region within the nucleus. In MCF7 cells, we show that this depends on the presence of estrogen. CONCLUSIONS Our data suggest that the liganded estrogen receptor is linked to long-range changes in higher-order chromatin organization and epigenetic dysregulation in cancer. This may suggest that as well as drugs targeting histone modifications, it will be valuable to investigate the inhibition of protein complexes involved in chromatin folding in cancer cells.
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Affiliation(s)
- Sehrish Rafique
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XU, UK. .,Edinburgh Breakthrough Research Unit and Edinburgh Cancer Centre, University of Edinburgh, Western General Hospital, Crewe Road South, Edinburgh, Scotland, EH4 2XU, UK.
| | - Jeremy S Thomas
- Edinburgh Breakthrough Research Unit and Edinburgh Cancer Centre, University of Edinburgh, Western General Hospital, Crewe Road South, Edinburgh, Scotland, EH4 2XU, UK.
| | - Duncan Sproul
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XU, UK. .,Edinburgh Breakthrough Research Unit and Edinburgh Cancer Centre, University of Edinburgh, Western General Hospital, Crewe Road South, Edinburgh, Scotland, EH4 2XU, UK.
| | - Wendy A Bickmore
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XU, UK.
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236
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Abstract
Chromatin, once thought to serve only as a means to package DNA, is now recognized as a major regulator of gene activity. As a result of the wide range of methods used to describe the numerous levels of chromatin organization, the terminology that has emerged to describe these organizational states is often imprecise and sometimes misleading. In this review, we discuss our current understanding of chromatin architecture and propose terms to describe the various biochemical and structural states of chromatin.
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Affiliation(s)
- Liron Even-Faitelson
- Program in Genetics and Genome Biology, The Hospital for Sick Children, 686 Bay Street, Toronto, ON, M5G 0A4, Canada
| | | | - Zahra Baghestani
- Program in Genetics and Genome Biology, The Hospital for Sick Children, 686 Bay Street, Toronto, ON, M5G 0A4, Canada
| | - David P Bazett-Jones
- Program in Genetics and Genome Biology, The Hospital for Sick Children, 686 Bay Street, Toronto, ON, M5G 0A4, Canada.
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237
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Abstract
Recent investigations on 3D chromatin folding revealed that the eukaryote genomes are both highly compartmentalized and extremely dynamic. This review presents the most recent advances in topological domains' organization of the eukaryote genomes and discusses the relationship to chromatin loop formation. CTCF protein appears as a central factor of these two organization levels having either a strong insulating role at TAD borders, or a weaker architectural role in chromatin loop formation. TAD borders directly impact on chromatin dynamics by restricting contacts within specific genomic portions thus confining chromatin loop formation within TADs. We discuss how sub-TAD chromatin dynamics, constrained into a recently described statistical helix conformation, can produce functional interactions by contact stabilization.
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238
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Landeira D, Bagci H, Malinowski AR, Brown KE, Soza-Ried J, Feytout A, Webster Z, Ndjetehe E, Cantone I, Asenjo HG, Brockdorff N, Carroll T, Merkenschlager M, Fisher AG. Jarid2 Coordinates Nanog Expression and PCP/Wnt Signaling Required for Efficient ESC Differentiation and Early Embryo Development. Cell Rep 2015; 12:573-86. [PMID: 26190104 PMCID: PMC4534826 DOI: 10.1016/j.celrep.2015.06.060] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 06/10/2015] [Accepted: 06/22/2015] [Indexed: 12/31/2022] Open
Abstract
Jarid2 is part of the Polycomb Repressor complex 2 (PRC2) responsible for genome-wide H3K27me3 deposition. Unlike other PRC2-deficient embryonic stem cells (ESCs), however, Jarid2-deficient ESCs show a severe differentiation block, altered colony morphology, and distinctive patterns of deregulated gene expression. Here, we show that Jarid2−/− ESCs express constitutively high levels of Nanog but reduced PCP signaling components Wnt9a, Prickle1, and Fzd2 and lowered β-catenin activity. Depletion of Wnt9a/Prickle1/Fzd2 from wild-type ESCs or overexpression of Nanog largely phenocopies these cellular defects. Co-culture of Jarid2−/− with wild-type ESCs restores variable Nanog expression and β-catenin activity and can partially rescue the differentiation block of mutant cells. In addition, we show that ESCs lacking Jarid2 or Wnt9a/Prickle1/Fzd2 or overexpressing Nanog induce multiple ICM formation when injected into normal E3.5 blastocysts. These data describe a previously unrecognized role for Jarid2 in regulating a core pluripotency and Wnt/PCP signaling circuit that is important for ESC differentiation and for pre-implantation development. ESCs lacking Jarid2 show constitutive Nanog expression ESCs lacking Jarid2 have reduced PCP/Wnt signaling Co-culture of Jarid2-null and WT ESCs restores differentiation capability Jarid2-null ESCs form more than one ICM upon injection to E3.5 mouse blastocysts
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Affiliation(s)
- David Landeira
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK; Department of Computer Science and A. I., University of Granada, Centre for Genomics and Oncological Research (GENYO), Avenue de la Ilustracion 114, 18016 Granada, Spain.
| | - Hakan Bagci
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Andrzej R Malinowski
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Karen E Brown
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Jorge Soza-Ried
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Amelie Feytout
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Zoe Webster
- Transgenics and Embryonic Stem Cell Laboratory, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Elodie Ndjetehe
- Transgenics and Embryonic Stem Cell Laboratory, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Irene Cantone
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Helena G Asenjo
- Department of Computer Science and A. I., University of Granada, Centre for Genomics and Oncological Research (GENYO), Avenue de la Ilustracion 114, 18016 Granada, Spain
| | - Neil Brockdorff
- Developmental Epigenetics Group, Department of Biochemistry, University of Oxford, South Parks Road, Oxford 1 3QU, UK
| | - Thomas Carroll
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Matthias Merkenschlager
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Amanda G Fisher
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
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239
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Pengelly AR, Kalb R, Finkl K, Müller J. Transcriptional repression by PRC1 in the absence of H2A monoubiquitylation. Genes Dev 2015; 29:1487-92. [PMID: 26178786 PMCID: PMC4526733 DOI: 10.1101/gad.265439.115] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 06/24/2015] [Indexed: 11/25/2022]
Abstract
Histone H2A monoubiquitylation (H2Aub) is considered to be a key effector in transcriptional repression by Polycomb-repressive complex 1 (PRC1). We analyzed Drosophila with a point mutation in the PRC1 subunit Sce that abolishes its H2A ubiquitylase activity or with point mutations in the H2A and H2Av residues ubiquitylated by PRC1. H2Aub is essential for viability and required for efficient histone H3 Lys27 trimethylation by PRC2 early in embryogenesis. However, H2Aub-deficient animals fully maintain repression of PRC1 target genes and do not show phenotypes characteristic of Polycomb group mutants. PRC1 thus represses canonical target genes independently of H2Aub.
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Affiliation(s)
- Ana Raquel Pengelly
- Laboratory of Chromatin Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Reinhard Kalb
- Laboratory of Chromatin Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Katja Finkl
- Laboratory of Chromatin Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Jürg Müller
- Laboratory of Chromatin Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
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240
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One, Two, Three: Polycomb Proteins Hit All Dimensions of Gene Regulation. Genes (Basel) 2015; 6:520-42. [PMID: 26184319 PMCID: PMC4584315 DOI: 10.3390/genes6030520] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 06/30/2015] [Indexed: 12/16/2022] Open
Abstract
Polycomb group (PcG) proteins contribute to the formation and maintenance of a specific repressive chromatin state that prevents the expression of genes in a particular space and time. Polycomb repressive complexes (PRCs) consist of several PcG proteins with specific regulatory or catalytic properties. PRCs are recruited to thousands of target genes, and various recruitment factors, including DNA-binding proteins and non-coding RNAs, are involved in the targeting. PcG proteins contribute to a multitude of biological processes by altering chromatin features at different scales. PcG proteins mediate both biochemical modifications of histone tails and biophysical modifications (e.g., chromatin fiber compaction and three-dimensional (3D) chromatin conformation). Here, we review the role of PcG proteins in nuclear architecture, describing their impact on the structure of the chromatin fiber, on chromatin interactions, and on the spatial organization of the genome in nuclei. Although little is known about the role of plant PcG proteins in nuclear organization, much is known in the animal field, and we highlight similarities and differences in the roles of PcG proteins in 3D gene regulation in plants and animals.
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241
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Taherbhoy AM, Huang OW, Cochran AG. BMI1–RING1B is an autoinhibited RING E3 ubiquitin ligase. Nat Commun 2015; 6:7621. [DOI: 10.1038/ncomms8621] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 05/26/2015] [Indexed: 01/21/2023] Open
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Mozgova I, Köhler C, Hennig L. Keeping the gate closed: functions of the polycomb repressive complex PRC2 in development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 83:121-32. [PMID: 25762111 DOI: 10.1111/tpj.12828] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 05/08/2023]
Abstract
Plant ontogeny relies on the correct timing and sequence of transitions between individual developmental phases. These are specified by gene expression patterns that are established by the balanced action of activators and repressors. Polycomb repressive complexes (PRCs) represent an evolutionarily conserved system of epigenetic gene repression that governs the establishment and maintenance of cell, tissue and organ identity, contributing to the correct execution of the developmental programs. PRC2 is a four-subunit histone methyltransferase complex that catalyzes trimethylation of lysine 27 on histone H3 (H3K27me3), which contributes to the change of chromatin structure and long-lasting gene repression. Here, we review the composition and molecular function of the different known PRC2 complexes in plants, and focus on the role of PRC2 in mediating the establishment of different developmental phases and transitions between them.
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Affiliation(s)
- Iva Mozgova
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, SE-75007, Uppsala, Sweden
| | - Claudia Köhler
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, SE-75007, Uppsala, Sweden
| | - Lars Hennig
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, SE-75007, Uppsala, Sweden
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243
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Cancer-associated ASXL1 mutations may act as gain-of-function mutations of the ASXL1-BAP1 complex. Nat Commun 2015; 6:7307. [PMID: 26095772 PMCID: PMC4557297 DOI: 10.1038/ncomms8307] [Citation(s) in RCA: 149] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 04/27/2015] [Indexed: 12/29/2022] Open
Abstract
ASXL1 is the obligate regulatory subunit of a deubiquitinase complex whose catalytic subunit is BAP1. Heterozygous mutations of ASXL1 that result in premature truncations are frequent in myeloid leukemias and Bohring-Opitz syndrome. Here we demonstrate that ASXL1 truncations confer enhanced activity on the ASXL1-BAP1 complex. Stable expression of truncated, hyperactive ASXL1-BAP1 complexes in a haematopoietic precursor cell line results in global erasure of H2AK119Ub, striking depletion of H3K27me3, selective upregulation of a subset of genes whose promoters are marked by both H2AK119Ub and H3K4me3, and spontaneous differentiation to the mast cell lineage. These outcomes require the catalytic activity of BAP1, indicating that they are downstream consequences of H2AK119Ub erasure. In bone marrow precursors, expression of truncated ASXL1-BAP1 complex cooperates with TET2 loss-of-function to increase differentiation to the myeloid lineage in vivo. Our data raise the possibility that ASXL1 truncation mutations confer gain-of-function on the ASXL-BAP1 complex.
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244
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Mozzetta C, Pontis J, Ait-Si-Ali S. Functional Crosstalk Between Lysine Methyltransferases on Histone Substrates: The Case of G9A/GLP and Polycomb Repressive Complex 2. Antioxid Redox Signal 2015; 22:1365-81. [PMID: 25365549 PMCID: PMC4432786 DOI: 10.1089/ars.2014.6116] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
SIGNIFICANCE Methylation of histone H3 on lysine 9 and 27 (H3K9 and H3K27) are two epigenetic modifications that have been linked to several crucial biological processes, among which are transcriptional silencing and cell differentiation. RECENT ADVANCES Deposition of these marks is catalyzed by H3K9 lysine methyltransferases (KMTs) and polycomb repressive complex 2, respectively. Increasing evidence is emerging in favor of a functional crosstalk between these two major KMT families. CRITICAL ISSUES Here, we review the current knowledge on the mechanisms of action and function of these enzymes, with particular emphasis on their interplay in the regulation of chromatin states and biological processes. We outline their crucial roles played in tissue homeostasis, by controlling the fate of embryonic and tissue-specific stem cells, highlighting how their deregulation is often linked to the emergence of a number of malignancies and neurological disorders. FUTURE DIRECTIONS Histone methyltransferases are starting to be tested as drug targets. A new generation of highly selective chemical inhibitors is starting to emerge. These hold great promise for a rapid translation of targeting epigenetic drugs into clinical practice for a number of aggressive cancers and neurological disorders.
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Affiliation(s)
- Chiara Mozzetta
- Laboratoire Epigénétique et Destin Cellulaire, UMR7216, Centre National de la Recherche Scientifique CNRS, Université Paris Diderot , Sorbonne Paris Cité, Paris, France
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245
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Abstract
In multicellular organisms differentiated cells must maintain their cellular memory, which will be faithfully inherited and maintained by their progeny. In addition, these specialized cells are exposed to specific environmental and cell-intrinsic signals and will have to appropriately respond to them. Some of these stimuli lead to changes in a subset of genes or to a genome-wide reprogramming of the cells that will remain after stimuli removal and, in some instances, will be inherited by the daughter cells. The molecular substrate that integrates cellular memory and plasticity is the chromatin, a complex of DNA and histones unique to eukaryotes. The nucleosome is the fundamental unit of the chromatin and nucleosomal organization defines different chromatin conformations. Chromatin regulators affect chromatin conformation and accessibility by covalently modifying the DNA or the histones, substituting histone variants, remodeling the nucleosome position or modulating chromatin looping and folding. These regulators frequently act in multiprotein complexes and highly specific interplays among chromatin marks and different chromatin regulators allow a remarkable array of possibilities. Therefore, chromatin regulator nets act to propagate the conformation of different chromatin regions through DNA replication and mitosis, and to remodel the chromatin fiber to regulate the accessibility of the DNA to transcription factors and to the transcription and repair machineries. Here, the state-of-the-art of the best-known chromatin regulators is reviewed.
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246
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Abstract
The multiple lineages and differentiation states that constitute the T-cell compartment all derive from a common thymic precursor. These distinct transcriptional states are maintained both in time and after multiple rounds of cell division by the concerted actions of a small set of lineage-defining transcription factors that act in conjunction with a suite of chromatin-modifying enzymes to activate, repress, and fine-tune gene expression. These chromatin modifications collectively provide an epigenetic code that allows the stable and heritable maintenance of the T-cell phenotype. Recently, it has become apparent that the epigenetic code represents a therapeutic target for a variety of immune cell disorders, including lymphoma and acute and chronic inflammatory diseases. Here, we review the recent advances in epigenetic regulation of gene expression, particularly as it relates to the T-cell differentiation and function.
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Affiliation(s)
- Rhys S Allan
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Vic., Australia; Department of Medical Biology, The University of Melbourne, Parkville, Vic., Australia
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247
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Liu X, Zhou S, Wang W, Ye Y, Zhao Y, Xu Q, Zhou C, Tan F, Cheng S, Zhou DX. Regulation of histone methylation and reprogramming of gene expression in the rice inflorescence meristem. THE PLANT CELL 2015; 27:1428-44. [PMID: 25957386 PMCID: PMC4456649 DOI: 10.1105/tpc.15.00201] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 04/16/2015] [Accepted: 04/23/2015] [Indexed: 05/18/2023]
Abstract
Rice inflorescence meristem (IM) activity is essential for panicle development and grain production. How chromatin and epigenetic mechanisms regulate IM activity remains unclear. Genome-wide analysis revealed that in addition to genes involved in the vegetative to reproductive transition, many metabolic and protein synthetic genes were activated in IM compared with shoot apical meristem and that a change in the H3K27me3/H3K4me3 ratio was an important factor for the differential expression of many genes. Thousands of genes gained or lost H3K27me3 in IM, and downregulation of the H3K27 methyltransferase gene SET DOMAIN GROUP 711 (SDG711) or mutation of the H3K4 demethylase gene JMJ703 eliminated the increase of H3K27me3 in many genes. SDG711-mediated H3K27me3 repressed several important genes involved in IM activity and many genes that are silent in the IM but activated during floral organogenesis or other developmental stages. SDG711 overexpression augmented IM activity and increased panicle size; suppression of SDG711 by RNA interference had the opposite effect. Double knockdown/knockout of SDG711 and JMJ703 further reduced panicle size. These results suggest that SDG711 and JMJ703 have agonistic functions in reprogramming the H3K27me3/H3K4me3 ratio and modulating gene expression in the IM.
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Affiliation(s)
- Xiaoyun Liu
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Shaoli Zhou
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Wentao Wang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Yiran Ye
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Yu Zhao
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Qiutao Xu
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Chao Zhou
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Feng Tan
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Saifeng Cheng
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Dao-Xiu Zhou
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China Institute Plant Science Paris-Saclay (IPS2), Université Paris-sud 11, 91405 Orsay, France
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248
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Gorkin DU, Leung D, Ren B. The 3D genome in transcriptional regulation and pluripotency. Cell Stem Cell 2015; 14:762-75. [PMID: 24905166 DOI: 10.1016/j.stem.2014.05.017] [Citation(s) in RCA: 267] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
It can be convenient to think of the genome as simply a string of nucleotides, the linear order of which encodes an organism's genetic blueprint. However, the genome does not exist as a linear entity within cells where this blueprint is actually utilized. Inside the nucleus, the genome is organized in three-dimensional (3D) space, and lineage-specific transcriptional programs that direct stem cell fate are implemented in this native 3D context. Here, we review principles of 3D genome organization in mammalian cells. We focus on the emerging relationship between genome organization and lineage-specific transcriptional regulation, which we argue are inextricably linked.
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Affiliation(s)
- David U Gorkin
- Ludwig Institute for Cancer Research, 9500 Gilman Drive, La Jolla, CA 92093, USA.
| | - Danny Leung
- Ludwig Institute for Cancer Research, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Bing Ren
- Ludwig Institute for Cancer Research, 9500 Gilman Drive, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, Institute of Genome Medicine, Moores Cancer Center, University of California, San Diego, School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA.
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249
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Sanli I, Feil R. Chromatin mechanisms in the developmental control of imprinted gene expression. Int J Biochem Cell Biol 2015; 67:139-47. [PMID: 25908531 DOI: 10.1016/j.biocel.2015.04.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 04/08/2015] [Indexed: 10/23/2022]
Abstract
Hundreds of protein-coding genes and regulatory non-coding RNAs (ncRNAs) are subject to genomic imprinting. The mono-allelic DNA methylation marks that control imprinted gene expression are somatically maintained throughout development, and this process is linked to specific chromatin features. Yet, at many imprinted genes, the mono-allelic expression is lineage or tissue-specific. Recent studies provide mechanistic insights into the developmentally-restricted action of the 'imprinting control regions' (ICRs). At several imprinted domains, the ICR expresses a long ncRNA that mediates chromatin repression in cis (and probably in trans as well). ICRs at other imprinted domains mediate higher-order chromatin structuration that enhances, or prevents, transcription of close-by genes. Here, we present how chromatin and ncRNAs contribute to developmental control of imprinted gene expression and discuss implications for disease. This article is part of a Directed Issue entitled: Epigenetics dynamics in development and disease.
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Affiliation(s)
- Ildem Sanli
- Institute of Molecular Genetics (IGMM), UMR-5535, CNRS, University of Montpellier, 1919 route de Mende, 34293 Montpellier, France
| | - Robert Feil
- Institute of Molecular Genetics (IGMM), UMR-5535, CNRS, University of Montpellier, 1919 route de Mende, 34293 Montpellier, France.
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250
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Battulin N, Fishman VS, Mazur AM, Pomaznoy M, Khabarova AA, Afonnikov DA, Prokhortchouk EB, Serov OL. Comparison of the three-dimensional organization of sperm and fibroblast genomes using the Hi-C approach. Genome Biol 2015; 16:77. [PMID: 25886366 PMCID: PMC4434584 DOI: 10.1186/s13059-015-0642-0] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 03/23/2015] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The three-dimensional organization of the genome is tightly connected to its biological function. The Hi-C approach was recently introduced as a method that can be used to identify higher-order chromatin interactions genome-wide. The aim of this study was to determine genome-wide chromatin interaction frequencies using the Hi-C approach in mouse sperm cells and embryonic fibroblasts. RESULTS The obtained data demonstrate that the three-dimensional genome organizations of sperm and fibroblast cells show a high degree of similarity both with each other and with the previously described mouse embryonic stem cells. Both A- and B-compartments and topologically associated domains are present in spermatozoa and fibroblasts. Nevertheless, sperm cells and fibroblasts exhibit statistically significant differences between each other in the contact probabilities of defined loci. Tight packaging of the sperm genome results in an enrichment of long-range contacts compared with the fibroblasts. However, only 30% of the differences in the number of contacts are based on differences in the densities of their genome packages; the main source of the differences is the gain or loss of contacts that are specific for defined genome regions. We find that the dependence of the contact probability on genomic distance for sperm is close to the dependence predicted for the fractal globular folding of chromatin. CONCLUSIONS Overall, we can conclude that the three-dimensional structure of the genome is passed through generations without being dramatically changed in sperm cells.
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Affiliation(s)
- Nariman Battulin
- Institute of Cytology and Genetics, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Novosibirsk, 630090, Russia. .,Skoltech Center for Stem Cell Research, Skolkovo Institute of Science and Technology, Skolkovo 143025, Moscow, Russia.
| | - Veniamin S Fishman
- Institute of Cytology and Genetics, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Novosibirsk, 630090, Russia. .,Skoltech Center for Stem Cell Research, Skolkovo Institute of Science and Technology, Skolkovo 143025, Moscow, Russia.
| | - Alexander M Mazur
- Center 'Bioengineering', Russian Academy of Sciences, Moscow, 117312, Russia. .,Skoltech Center for Stem Cell Research, Skolkovo Institute of Science and Technology, Skolkovo 143025, Moscow, Russia.
| | - Mikhail Pomaznoy
- Institute of Cytology and Genetics, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Novosibirsk, 630090, Russia.
| | - Anna A Khabarova
- Institute of Cytology and Genetics, Novosibirsk, 630090, Russia. .,Skoltech Center for Stem Cell Research, Skolkovo Institute of Science and Technology, Skolkovo 143025, Moscow, Russia.
| | - Dmitry A Afonnikov
- Institute of Cytology and Genetics, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Novosibirsk, 630090, Russia. .,Skoltech Center for Stem Cell Research, Skolkovo Institute of Science and Technology, Skolkovo 143025, Moscow, Russia.
| | - Egor B Prokhortchouk
- Center 'Bioengineering', Russian Academy of Sciences, Moscow, 117312, Russia. .,National Research Center, Kurchatov Institute, Moscow, 123098, Russia. .,Skoltech Center for Stem Cell Research, Skolkovo Institute of Science and Technology, Skolkovo 143025, Moscow, Russia.
| | - Oleg L Serov
- Institute of Cytology and Genetics, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Novosibirsk, 630090, Russia. .,Skoltech Center for Stem Cell Research, Skolkovo Institute of Science and Technology, Skolkovo 143025, Moscow, Russia.
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