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Liu Y, Huang Y. Uncovering the mechanistic basis for specific recognition of monomethylated H3K4 by the CW domain of Arabidopsis histone methyltransferase SDG8. J Biol Chem 2018; 293:6470-6481. [PMID: 29496997 PMCID: PMC5925821 DOI: 10.1074/jbc.ra117.001390] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 02/26/2018] [Indexed: 01/07/2023] Open
Abstract
Chromatin consists of DNA and histones, and specific histone modifications that determine chromatin structure and activity are regulated by three types of proteins, called writer, reader, and eraser. Histone reader proteins from vertebrates, vertebrate-infecting parasites, and higher plants possess a CW domain, which has been reported to read histone H3 lysine 4 (H3K4). The CW domain of Arabidopsis SDG8 (also called ASHH2), a histone H3 lysine 36 methyltransferase, preferentially binds monomethylated H3K4 (H3K4me1), unlike the mammalian CW domain protein, which binds trimethylated H3K4 (H3K4me3). However, the molecular basis of the selective binding by the CW domain of SDG8 (SDG8-CW) remains unclear. Here, we solved the 1.6-Å-resolution structure of SDG8-CW in complex with H3K4me1, which revealed that residues in the C-terminal α-helix of SDG8-CW determine binding specificity for low methylation levels at H3K4. Moreover, substitutions of key residues, specifically Ile-915 and Asn-916, converted SDG8-CW binding preference from H3K4me1 to H3K4me3. Sequence alignment and mutagenesis studies revealed that the CW domain of SDG725, the homolog of SDG8 in rice, shares the same binding preference with SDG8-CW, indicating that preference for low methylated H3K4 by the CW domain of ASHH2 homologs is conserved among higher-order plants. Our findings provide first structural insights into the molecular basis for specific recognition of monomethylated H3K4 by the H3K4me1 reader protein SDG8 from Arabidopsis.
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Affiliation(s)
- Yanchao Liu
- From the State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Science Research Center, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 201210, China
| | - Ying Huang
- From the State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Science Research Center, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 201210, China, To whom correspondence should be addressed. Tel.:
86-20778200; Fax:
86-20778200; E-mail:
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Accessibility of the histone H3 tail in the nucleosome for binding of paired readers. Nat Commun 2017; 8:1489. [PMID: 29138400 PMCID: PMC5686127 DOI: 10.1038/s41467-017-01598-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 10/03/2017] [Indexed: 12/03/2022] Open
Abstract
Combinatorial polyvalent contacts of histone-binding domains or readers commonly mediate localization and activities of chromatin-associated proteins. A pair of readers, the PHD fingers of the protein CHD4, has been shown to bivalently recognize histone H3 tails. Here we describe a mechanism by which these linked but independent readers bind to the intact nucleosome core particle (NCP). Comprehensive NMR, chemical reactivity, molecular dynamics, and fluorescence analyses point to the critical roles of intra-nucleosomal histone-DNA interactions that reduce the accessibility of H3 tails in NCP, the nucleosomal DNA, and the linker between readers in modulating nucleosome- and/or histone-binding activities of the readers. We show that the second PHD finger of CHD4 initiates recruitment to the nucleosome, however both PHDs are required to alter the NCP dynamics. Our findings reveal a distinctive regulatory mechanism for the association of paired readers with the nucleosome that provides an intricate balance between cooperative and individual activities of the readers. The chromatin remodeller CHD4 contains two PHD finger reader domains that have been shown to bivalently recognize H3 histone tails. Here, the authors describe a mechanism by which the PHD fingers bind to the intact nucleosome core particle, revealing both cooperative and individual interactions.
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54
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Yung PYK, Elsässer SJ. Evolution of epigenetic chromatin states. Curr Opin Chem Biol 2017; 41:36-42. [PMID: 29078152 DOI: 10.1016/j.cbpa.2017.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 09/06/2017] [Accepted: 10/03/2017] [Indexed: 01/08/2023]
Abstract
The central dogma of gene expression entails the flow of genetic information from DNA to RNA, then to protein. Decades of studies on epigenetics have characterized an additional layer of information, where epigenetic states help to shape differential utilization of genetic information. Orchestrating conditional gene expressions to elicit a defined phenotype and function, epigenetics states distinguish different cell types or maintain a long-lived memory of past signals. Packaging the genetic information in the nucleus of the eukaryotic cell, chromatin provides a large regulatory repertoire that capacitates the genome to give rise to many distinct epigenomes. We will discuss how reversible, heritable functional annotation mechanisms in chromatin may have evolved from basic chemical diversification of the underlying molecules.
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Affiliation(s)
- Philip Yuk Kwong Yung
- Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Simon J Elsässer
- Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
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Structure and mechanism of plant histone mark readers. SCIENCE CHINA-LIFE SCIENCES 2017; 61:170-177. [PMID: 29019143 DOI: 10.1007/s11427-017-9163-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 08/11/2017] [Indexed: 10/18/2022]
Abstract
In eukaryotes, epigenetic-based mechanisms are involved in almost all the important biological processes. Amongst different epigenetic regulation pathways, the dynamic covalent modifications on histones are the most extensively investigated and characterized types. The covalent modifications on histone can be "read" by specific protein domains and then subsequently trigger downstream signaling events. Plants generally possess epigenetic regulation systems similar to animals and fungi, but also exhibit some plant-specific features. Similar to animals and fungi, plants require distinct protein domains to specifically "read" modified histones in both modification-specific and sequence-specific manners. In this review, we will focus on recent progress of the structural studies on the recognition of the epigenetic marks on histones by plant reader proteins, and further summarize the general and exceptional features of plant histone mark readers.
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Structure of the Dnmt1 Reader Module Complexed with a Unique Two-Mono-Ubiquitin Mark on Histone H3 Reveals the Basis for DNA Methylation Maintenance. Mol Cell 2017; 68:350-360.e7. [DOI: 10.1016/j.molcel.2017.09.037] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 08/03/2017] [Accepted: 09/27/2017] [Indexed: 11/18/2022]
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Bromodomain Histone Readers and Cancer. J Mol Biol 2017; 429:2003-2010. [DOI: 10.1016/j.jmb.2016.11.020] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/15/2016] [Accepted: 11/19/2016] [Indexed: 12/29/2022]
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58
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Mechanisms Governing Precise Protein Biotinylation. Trends Biochem Sci 2017; 42:383-394. [DOI: 10.1016/j.tibs.2017.02.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 01/25/2017] [Accepted: 02/03/2017] [Indexed: 12/26/2022]
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59
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Effects of histone deacetylase inhibitory prodrugs on epigenetic changes and DNA damage response in tumor and heart of glioblastoma xenograft. Invest New Drugs 2017; 35:412-426. [DOI: 10.1007/s10637-017-0448-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Accepted: 03/01/2017] [Indexed: 12/22/2022]
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Shanle EK, Shinsky SA, Bridgers JB, Bae N, Sagum C, Krajewski K, Rothbart SB, Bedford MT, Strahl BD. Histone peptide microarray screen of chromo and Tudor domains defines new histone lysine methylation interactions. Epigenetics Chromatin 2017; 10:12. [PMID: 28293301 PMCID: PMC5348760 DOI: 10.1186/s13072-017-0117-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 03/01/2017] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Histone posttranslational modifications (PTMs) function to regulate chromatin structure and function in part through the recruitment of effector proteins that harbor specialized "reader" domains. Despite efforts to elucidate reader domain-PTM interactions, the influence of neighboring PTMs and the target specificity of many reader domains is still unclear. The aim of this study was to use a high-throughput histone peptide microarray platform to interrogate 83 known and putative histone reader domains from the chromo and Tudor domain families to identify their interactions and characterize the influence of neighboring PTMs on these interactions. RESULTS Nearly a quarter of the chromo and Tudor domains screened showed interactions with histone PTMs by peptide microarray, revealing known and several novel methyllysine interactions. Specifically, we found that the CBX/HP1 chromodomains that recognize H3K9me also recognize H3K23me2/3-a poorly understood histone PTM. We also observed that, in addition to their interaction with H3K4me3, Tudor domains of the Spindlin family also recognized H4K20me3-a previously uncharacterized interaction. Several Tudor domains also showed novel interactions with H3K4me as well. CONCLUSIONS These results provide an important resource for the epigenetics and chromatin community on the interactions of many human chromo and Tudor domains. They also provide the basis for additional studies into the functional significance of the novel interactions that were discovered.
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Affiliation(s)
- Erin K Shanle
- Department of Biological and Environmental Sciences, Longwood University, Farmville, VA 23909 USA
| | - Stephen A Shinsky
- Department of Biochemistry and Biophysics, The University of North Carolina, Chapel Hill, NC 27599 USA.,Lineberger Comprehensive Cancer Center, The University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA.,Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA USA
| | - Joseph B Bridgers
- Department of Biochemistry and Biophysics, The University of North Carolina, Chapel Hill, NC 27599 USA
| | - Narkhyun Bae
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957 USA
| | - Cari Sagum
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957 USA
| | - Krzysztof Krajewski
- Department of Biochemistry and Biophysics, The University of North Carolina, Chapel Hill, NC 27599 USA
| | - Scott B Rothbart
- Center for Epigenetics, Van Andel Research Institute, Grand Rapids, MI 49503 USA
| | - Mark T Bedford
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX 78957 USA
| | - Brian D Strahl
- Department of Biochemistry and Biophysics, The University of North Carolina, Chapel Hill, NC 27599 USA.,Lineberger Comprehensive Cancer Center, The University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA
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61
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Yu H, Jiang Y, Liu L, Shan W, Chu X, Yang Z, Yang ZQ. Integrative genomic and transcriptomic analysis for pinpointing recurrent alterations of plant homeodomain genes and their clinical significance in breast cancer. Oncotarget 2017; 8:13099-13115. [PMID: 28055972 PMCID: PMC5355080 DOI: 10.18632/oncotarget.14402] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 12/05/2016] [Indexed: 11/29/2022] Open
Abstract
A wide range of the epigenetic effectors that regulate chromatin modification, gene expression, genomic stability, and DNA repair contain structurally conserved domains called plant homeodomain (PHD) fingers. Alternations of several PHD finger-containing proteins (PHFs) due to genomic amplification, mutations, deletions, and translocations have been linked directly to various types of cancer. However, little is known about the genomic landscape and the clinical significance of PHFs in breast cancer. Hence, we performed a large-scale genomic and transcriptomic analysis of 98 PHF genes in breast cancer using TCGA and METABRIC datasets and correlated the recurrent alterations with clinicopathological features and survival of patients. Different subtypes of breast cancer had different patterns of copy number and expression for each PHF. We identified a subset of PHF genes that was recurrently altered with high prevalence, including PYGO2 (pygopus family PHD finger 2), ZMYND8 (zinc finger, MYND-type containing 8), ASXL1 (additional sex combs like 1) and CHD3 (chromodomain helicase DNA binding protein 3). Copy number increase and overexpression of ZMYND8 were more prevalent in Luminal B subtypes and were significantly associated with shorter survival of breast cancer patients. ZMYND8 was also involved in a positive feedback circuit of the estrogen receptor (ER) pathway, and the expression of ZMYND8 was repressed by the bromodomain and extra terminal (BET) inhibitor in breast cancer. Our findings suggest a promising avenue for future research-to focus on a subset of PHFs to better understand the molecular mechanisms and to identify therapeutic targets in breast cancer.
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Affiliation(s)
- Huimei Yu
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA
- College of Basic Medicine, Jilin University, Changchun, China
| | - Yuanyuan Jiang
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Lanxin Liu
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Wenqi Shan
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Xiaofang Chu
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Zhe Yang
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Zeng-Quan Yang
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI 48201, USA
- Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, MI 48201, USA
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Abstract
SUMMARYEpigenetic changes are present in all human cancers and are now known to cooperate with genetic alterations to drive the cancer phenotype. These changes involve DNA methylation, histone modifiers and readers, chromatin remodelers, microRNAs, and other components of chromatin. Cancer genetics and epigenetics are inextricably linked in generating the malignant phenotype; epigenetic changes can cause mutations in genes, and, conversely, mutations are frequently observed in genes that modify the epigenome. Epigenetic therapies, in which the goal is to reverse these changes, are now one standard of care for a preleukemic disorder and form of lymphoma. The application of epigenetic therapies in the treatment of solid tumors is also emerging as a viable therapeutic route.
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Affiliation(s)
- Stephen B Baylin
- Cancer Biology Program, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21287
| | - Peter A Jones
- Van Andel Research Institute, Grand Rapids, Michigan 49503
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63
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Vasudevan D, Bovee RC, Thomas DD. Nitric oxide, the new architect of epigenetic landscapes. Nitric Oxide 2016; 59:54-62. [PMID: 27553128 DOI: 10.1016/j.niox.2016.08.002] [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] [Received: 07/10/2016] [Accepted: 08/18/2016] [Indexed: 12/13/2022]
Abstract
Nitric oxide (NO) is an endogenously produced signaling molecule with multiple regulatory functions in physiology and disease. The most studied molecular mechanisms underlying the biological functions of NO include its reaction with heme proteins and regulation of protein activity via modification of thiol residues. A significant number of transcriptional responses and phenotypes observed in NO microenvironments, however, still lack mechanistic understanding. Recent studies shed new light on NO signaling by revealing its influence on epigenetic changes within the cell. Epigenetic alterations are important determinants of transcriptional responses and cell phenotypes, which can relay heritable information during cell division. As transcription across the genome is highly sensitive to these upstream epigenetic changes, this mode of NO signaling provides an alternate explanation for NO-mediated gene expression changes and phenotypes. This review will provide an overview of the interplay between NO and epigenetics as well as emphasize the unprecedented importance of these pathways to explain phenotypic effects associated with biological NO synthesis.
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Affiliation(s)
- Divya Vasudevan
- Department of Urology, Weill Cornell Medical College, New York, NY 10021, USA
| | - Rhea C Bovee
- Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Douglas D Thomas
- Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, Chicago, IL 60612, USA.
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Abstract
Over the past 20 years, breakthrough discoveries of chromatin-modifying enzymes and associated mechanisms that alter chromatin in response to physiological or pathological signals have transformed our knowledge of epigenetics from a collection of curious biological phenomena to a functionally dissected research field. Here, we provide a personal perspective on the development of epigenetics, from its historical origins to what we define as 'the modern era of epigenetic research'. We primarily highlight key molecular mechanisms of and conceptual advances in epigenetic control that have changed our understanding of normal and perturbed development.
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Affiliation(s)
- C David Allis
- Laboratory of Chromatin Biology and Epigenetics, The Rockefeller University, 1230 York Avenue, New York 10065, New York, USA
| | - Thomas Jenuwein
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, Freiburg D-79108, Germany
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65
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Abstract
Histone posttranslational modifications represent a versatile set of epigenetic marks involved not only in dynamic cellular processes, such as transcription and DNA repair, but also in the stable maintenance of repressive chromatin. In this article, we review many of the key and newly identified histone modifications known to be deregulated in cancer and how this impacts function. The latter part of the article addresses the challenges and current status of the epigenetic drug development process as it applies to cancer therapeutics.
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Affiliation(s)
- James E Audia
- Constellation Pharmaceuticals, Cambridge, Massachusetts 02142
| | - Robert M Campbell
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, Indiana 46285
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66
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Kingston RE, Tamkun JW. Transcriptional regulation by trithorax-group proteins. Cold Spring Harb Perspect Biol 2014; 6:a019349. [PMID: 25274705 DOI: 10.1101/cshperspect.a019349] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The trithorax group of genes (trxG) was identified in mutational screens that examined developmental phenotypes and suppression of Polycomb mutant phenotypes. The protein products of these genes are primarily involved in gene activation, although some can also have repressive effects. There is no central function for these proteins. Some move nucleosomes about on the genome in an ATP-dependent manner, some covalently modify histones such as methylating lysine 4 of histone H3, and some directly interact with the transcription machinery or are a part of that machinery. It is interesting to consider why these specific members of large families of functionally related proteins have strong developmental phenotypes.
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Affiliation(s)
- Robert E Kingston
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114
| | - John W Tamkun
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, California 95064
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67
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Cheng X. Structural and functional coordination of DNA and histone methylation. Cold Spring Harb Perspect Biol 2014; 6:6/8/a018747. [PMID: 25085914 DOI: 10.1101/cshperspect.a018747] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
One of the most fundamental questions in the control of gene expression in mammals is how epigenetic methylation patterns of DNA and histones are established, erased, and recognized. This central process in controlling gene expression includes coordinated covalent modifications of DNA and its associated histones. This article focuses on structural aspects of enzymatic activities of histone (arginine and lysine) methylation and demethylation and functional links between the methylation status of the DNA and histones. An interconnected network of methyltransferases, demethylases, and accessory proteins is responsible for changing or maintaining the modification status of specific regions of chromatin.
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Affiliation(s)
- Xiaodong Cheng
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
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68
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Abstract
Research using ciliates revealed early examples of epigenetic phenomena and continues to provide novel findings. These protozoans maintain separate germline and somatic nuclei that carry transcriptionally silent and active genomes, respectively. Examining the differences in chromatin within distinct nuclei of Tetrahymena identified histone variants and established that transcriptional regulators act by modifying histones. Formation of somatic nuclei requires both transcriptional activation of silent chromatin and large-scale DNA elimination. This somatic genome remodeling is directed by homologous RNAs, acting with an RNA interference (RNAi)-related machinery. Furthermore, the content of the parental somatic genome provides a homologous template to guide this genome restructuring. The mechanisms regulating ciliate DNA rearrangements reveal the surprising power of homologous RNAs to remodel the genome and transmit information transgenerationally.
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Affiliation(s)
- Douglas L Chalker
- Department of Biology, Washington University, St. Louis, Missouri 63130
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69
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Abstract
Eukaryotic chromatin is kept flexible and dynamic to respond to environmental, metabolic, and developmental cues through the action of a family of so-called "nucleosome remodeling" ATPases. Consistent with their helicase ancestry, these enzymes experience conformation changes as they bind and hydrolyze ATP. At the same time they interact with DNA and histones, which alters histone-DNA interactions in target nucleosomes. Their action may lead to complete or partial disassembly of nucleosomes, the exchange of histones for variants, the assembly of nucleosomes, or the movement of histone octamers on DNA. "Remodeling" may render DNA sequences accessible to interacting proteins or, conversely, promote packing into tightly folded structures. Remodeling processes participate in every aspect of genome function. Remodeling activities are commonly integrated with other mechanisms such as histone modifications or RNA metabolism to assemble stable, epigenetic states.
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70
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Elgin SCR, Reuter G. Position-effect variegation, heterochromatin formation, and gene silencing in Drosophila. Cold Spring Harb Perspect Biol 2013; 5:a017780. [PMID: 23906716 DOI: 10.1101/cshperspect.a017780] [Citation(s) in RCA: 309] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Position-effect variegation (PEV) results when a gene normally in euchromatin is juxtaposed with heterochromatin by rearrangement or transposition. When heterochromatin packaging spreads across the heterochromatin/euchromatin border, it causes transcriptional silencing in a stochastic pattern. PEV is intensely studied in Drosophila using the white gene. Screens for dominant mutations that suppress or enhance white variegation have identified many conserved epigenetic factors, including the histone H3 lysine 9 methyltransferase SU(VAR)3-9. Heterochromatin protein HP1a binds H3K9me2/3 and interacts with SU(VAR)3-9, creating a core memory system. Genetic, molecular, and biochemical analysis of PEV in Drosophila has contributed many key findings concerning establishment and maintenance of heterochromatin with concomitant gene silencing.
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Affiliation(s)
- Sarah C R Elgin
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
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