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Abstract
Histone variants are an important part of the histone contribution to chromatin epigenetics. In this review, we describe how the known structural differences of these variants from their canonical histone counterparts impart a chromatin signature ultimately responsible for their epigenetic contribution. In terms of the core histones, H2A histone variants are major players while H3 variant CenH3, with a controversial role in the nucleosome conformation, remains the genuine epigenetic histone variant. Linker histone variants (histone H1 family) haven’t often been studied for their role in epigenetics. However, the micro-heterogeneity of the somatic canonical forms of linker histones appears to play an important role in maintaining the cell-differentiated states, while the cell cycle independent linker histone variants are involved in development. A picture starts to emerge in which histone H2A variants, in addition to their individual specific contributions to the nucleosome structure and dynamics, globally impair the accessibility of linker histones to defined chromatin locations and may have important consequences for determining different states of chromatin metabolism.
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Affiliation(s)
- Manjinder S Cheema
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W-3P6, Canada.
| | - Juan Ausió
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W-3P6, Canada.
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52
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Kawashima T, Lorković ZJ, Nishihama R, Ishizaki K, Axelsson E, Yelagandula R, Kohchi T, Berger F. Diversification of histone H2A variants during plant evolution. TRENDS IN PLANT SCIENCE 2015; 20:419-25. [PMID: 25983206 DOI: 10.1016/j.tplants.2015.04.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 04/11/2015] [Accepted: 04/13/2015] [Indexed: 05/19/2023]
Abstract
Among eukaryotes, the four core histones show an extremely high conservation of their structure and form nucleosomes that compact, protect, and regulate access to genetic information. Nevertheless, in multicellular eukaryotes the two families, histone H2A and histone H3, have diversified significantly in key residues. We present a phylogenetic analysis across the green plant lineage that reveals an early diversification of the H2A family in unicellular green algae and remarkable expansions of H2A variants in flowering plants. We define motifs and domains that differentiate plant H2A proteins into distinct variant classes. In non-flowering land plants, we identify a new class of H2A variants and propose their possible role in the emergence of the H2A.W variant class in flowering plants.
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Affiliation(s)
- Tomokazu Kawashima
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Zdravko J Lorković
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Ryuichi Nishihama
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | | | - Elin Axelsson
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Ramesh Yelagandula
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Takayuki Kohchi
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Frederic Berger
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria.
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53
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Saade E, Pirozhkova I, Aimbetov R, Lipinski M, Ogryzko V. Molecular turnover, the H3.3 dilemma and organismal aging (hypothesis). Aging Cell 2015; 14:322-33. [PMID: 25720734 PMCID: PMC4406661 DOI: 10.1111/acel.12332] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/28/2015] [Indexed: 12/22/2022] Open
Abstract
The H3.3 histone variant has been a subject of increasing interest in the field of chromatin studies due to its two distinguishing features. First, its incorporation into chromatin is replication independent unlike the replication-coupled deposition of its canonical counterparts H3.1/2. Second, H3.3 has been consistently associated with an active state of chromatin. In accordance, this histone variant should be expected to be causally involved in the regulation of gene expression, or more generally, its incorporation should have downstream consequences for the structure and function of chromatin. This, however, leads to an apparent paradox: In cells that slowly replicate in the organism, H3.3 will accumulate with time, opening the way to aberrant effects on heterochromatin. Here, we review the indications that H3.3 is expected both to be incorporated in the heterochromatin of slowly replicating cells and to retain its functional downstream effects. Implications for organismal aging are discussed.
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Affiliation(s)
- Evelyne Saade
- Faculty of Public Health Lebanese University LU Beirut Lebanon
| | - Iryna Pirozhkova
- Institute Gustave Roussy University Paris SUD 114, rue Edouard Vaillant Villejuif 94805France
| | - Rakhan Aimbetov
- Institute Gustave Roussy University Paris SUD 114, rue Edouard Vaillant Villejuif 94805France
| | - Marc Lipinski
- Institute Gustave Roussy University Paris SUD 114, rue Edouard Vaillant Villejuif 94805France
| | - Vasily Ogryzko
- Institute Gustave Roussy University Paris SUD 114, rue Edouard Vaillant Villejuif 94805France
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54
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Acetylation of intragenic histones on HPV16 correlates with enhanced HPV16 gene expression. Virology 2015; 482:244-59. [PMID: 25900886 DOI: 10.1016/j.virol.2015.02.053] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 01/23/2015] [Accepted: 02/25/2015] [Indexed: 11/21/2022]
Abstract
We report that many histone modifications are unevenly distributed over the HPV16 genome in cervical cancer cells as well as in HPV16-immortalized keratinocytes. For example, H3K36me3 and H3K9Ac that are common in highly expressed cellular genes and over exons, were more common in the early than in the late region of the HPV16 genome. In contrast, H3K9me3, H4K20me3, H2BK5me1 and H4K16Ac were more frequent in the HPV16 late region. Furthermore, a region encompassing the HPV16 early polyadenylation signal pAE displayed high levels of histone H3 acetylation. Histone deacetylase (HDAC) inhibitors caused a 2- to 8-fold induction of HPV16 early and late mRNAs in cervical cancer cells and in immortalized keratinocytes, while at the same time increasing the levels of acetylated histones in the cells and on the HPV16 genome specifically. We concluded that increased histone acetylation on the HPV16 genome correlates with increased HPV16 gene expression.
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55
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Won KJ, Choi I, LeRoy G, Zee BM, Sidoli S, Gonzales-Cope M, Garcia BA. Proteogenomics analysis reveals specific genomic orientations of distal regulatory regions composed by non-canonical histone variants. Epigenetics Chromatin 2015; 8:13. [PMID: 25878728 PMCID: PMC4397702 DOI: 10.1186/s13072-015-0005-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 03/19/2015] [Indexed: 01/05/2023] Open
Abstract
Background Histone variants play further important roles in DNA packaging and controlling gene expression. However, our understanding about their composition and their functions is limited. Results Integrating proteomic and genomic approaches, we performed a comprehensive analysis of the epigenetic landscapes containing the four histone variants H3.1, H3.3, H2A.Z, and macroH2A. These histones were FLAG-tagged in HeLa cells and purified using chromatin immunoprecipitation (ChIP). By adopting ChIP followed by mass spectrometry (ChIP-MS), we quantified histone post-translational modifications (PTMs) and histone variant nucleosomal ratios in highly purified mononucleosomes. Subsequent ChIP followed by next-generation sequencing (ChIP-seq) was used to map the genome-wide localization of the analyzed histone variants and define their chromatin domains. Finally, we included in our study large datasets contained in the ENCODE database. We newly identified a group of regulatory regions enriched in H3.1 and the histone variant associated with repressive marks macroH2A. Systematic analysis identified both symmetric and asymmetric patterns of histone variant occupancies at intergenic regulatory regions. Strikingly, these directional patterns were associated with RNA polymerase II (PolII). These asymmetric patterns correlated with the enhancer activities measured using global run-on sequencing (GRO-seq) data. Conclusions Our studies show that H2A.Z and H3.3 delineate the orientation of transcription at enhancers as observed at promoters. We also showed that enhancers with skewed histone variant patterns well facilitate enhancer activity. Collectively, our study indicates that histone variants are deposited at regulatory regions to assist gene regulation. Electronic supplementary material The online version of this article (doi:10.1186/s13072-015-0005-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kyoung-Jae Won
- The Institute for Diabetes, Obesity, and Metabolism, Philadelphia, PA 19104 USA.,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Inchan Choi
- The Institute for Diabetes, Obesity, and Metabolism, Philadelphia, PA 19104 USA.,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA.,Department of Agricultural Biotechnology, National Academy of Agricultural Science, 370 Nongsaengmyeong-ro, Wansan-gu, Jeonju-si, Jeollabuk-do 560-500 South Korea
| | - Gary LeRoy
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544 USA
| | - Barry M Zee
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544 USA.,Epigenetics Program, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Simone Sidoli
- Epigenetics Program, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Michelle Gonzales-Cope
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544 USA.,Epigenetics Program, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Benjamin A Garcia
- Epigenetics Program, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
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56
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Chemical “Diversity” of Chromatin Through Histone Variants and Histone Modifications. ACTA ACUST UNITED AC 2015. [DOI: 10.1007/s40610-015-0005-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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57
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Distinct features of the histone core structure in nucleosomes containing the histone H2A.B variant. Biophys J 2014; 106:2206-13. [PMID: 24853749 DOI: 10.1016/j.bpj.2014.04.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 03/23/2014] [Accepted: 04/01/2014] [Indexed: 11/24/2022] Open
Abstract
Nucleosomes containing a human histone variant, H2A.B, in an aqueous solution were analyzed by small-angle neutron scattering utilizing a contrast variation technique. Comparisons with the canonical H2A nucleosome structure revealed that the DNA termini of the H2A.B nucleosome are detached from the histone core surface, and flexibly expanded toward the solvent. In contrast, the histone tails are compacted in H2A.B nucleosomes compared to those in canonical H2A nucleosomes, suggesting that they bind to the surface of the histone core and/or DNA. Therefore, the histone tail dynamics may function to regulate the flexibility of the DNA termini in the nucleosomes.
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58
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Huang Y, Yao X, Wang G. 'Mediator-ing' messenger RNA processing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 6:257-69. [PMID: 25515410 DOI: 10.1002/wrna.1273] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 09/29/2014] [Accepted: 10/17/2014] [Indexed: 12/27/2022]
Abstract
Pre-messenger RNA (mRNA) processing, generally including capping, mRNA splicing, and cleavage-polyadenylation, is physically and functionally associated with transcription. The reciprocal coupling between transcription and mRNA processing ensures the efficient and regulated gene expression and editing. Multiple transcription factors/cofactors and mRNA processing factors are involved in the coupling process. This review focuses on several classic examples and recent advances that enlarge our understanding of how the transcriptional factors or cofactors, especially the Mediator complex, contribute to the RNA Pol II elongation, mRNA splicing, and polyadenylation.
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Affiliation(s)
- Yan Huang
- Key Laboratory of Gene Engineering of the Ministry of Education and State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
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59
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Sadakierska-Chudy A, Kostrzewa RM, Filip M. A comprehensive view of the epigenetic landscape part I: DNA methylation, passive and active DNA demethylation pathways and histone variants. Neurotox Res 2014; 27:84-97. [PMID: 25362550 PMCID: PMC4286137 DOI: 10.1007/s12640-014-9497-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 10/07/2014] [Accepted: 10/16/2014] [Indexed: 12/31/2022]
Abstract
In multicellular organisms, all the cells are genetically identical but turn genes on or off at the right time to promote differentiation into specific cell types. The regulation of higher-order chromatin structure is essential for genome-wide reprogramming and for tissue-specific patterns of gene expression. The complexity of the genome is regulated by epigenetic mechanisms, which act at the level of DNA, histones, and nucleosomes. Epigenetic machinery is involved in many biological processes, including genomic imprinting, X-chromosome inactivation, heterochromatin formation, and transcriptional regulation, as well as DNA damage repair. In this review, we summarize the recent understanding of DNA methylation, cytosine derivatives, active and passive demethylation pathways as well as histone variants. DNA methylation is one of the well-characterized epigenetic signaling tools. Cytosine methylation of promoter regions usually represses transcription but methylation in the gene body may have a positive correlation with gene expression. The attachment of a methyl group to cytosine residue in the DNA sequence is catalyzed by enzymes of the DNA methyltransferase family. Recent studies have shown that the Ten-Eleven translocation family enzymes are involved in stepwise oxidation of 5-methylcytosine, creating new cytosine derivatives including 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine. Additionally, histone variants into nucleosomes create another strategy to regulate the structure and function of chromatin. The replacement of canonical histones with specialized histone variants regulates accessibility of DNA, and thus may affect multiple biological processes, such as replication, transcription, DNA repair, and play a role in various disorders such as cancer.
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Affiliation(s)
- Anna Sadakierska-Chudy
- Laboratory of Drug Addiction Pharmacology, Institute of Pharmacology Polish Academy of Sciences, Smetna Street 12, 31-343, Kraków, Poland,
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60
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Batsché E, Ameyar-Zazoua M. The influence of Argonaute proteins on alternative RNA splicing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 6:141-56. [DOI: 10.1002/wrna.1264] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 07/28/2014] [Accepted: 07/31/2014] [Indexed: 12/20/2022]
Affiliation(s)
- Eric Batsché
- Institut Pasteur, Dpt Biologie du Développement et Cellules Souches; Unité de Régulation Epigénétique; 75015 Paris France
- URA2578; CNRS
| | - Maya Ameyar-Zazoua
- Institut Pasteur, Dpt Biologie du Développement et Cellules Souches; Unité de Régulation Epigénétique; 75015 Paris France
- URA2578; CNRS
- Laboratoire Epigénétique et Destin Cellulaire, CNRS UMR7216; Université Paris Diderot, Cité Sorbonne Paris; Paris France
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61
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West JA, Cook A, Alver BH, Stadtfeld M, Deaton AM, Hochedlinger K, Park PJ, Tolstorukov MY, Kingston RE. Nucleosomal occupancy changes locally over key regulatory regions during cell differentiation and reprogramming. Nat Commun 2014; 5:4719. [PMID: 25158628 PMCID: PMC4217530 DOI: 10.1038/ncomms5719] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Accepted: 07/16/2014] [Indexed: 01/23/2023] Open
Abstract
Chromatin structure determines DNA accessibility. We compare nucleosome occupancy in mouse and human embryonic stem cells (ESCs), induced-pluripotent stem cells (iPSCs) and differentiated cell types using MNase-seq. To address variability inherent in this technique, we developed a bioinformatic approach to identify regions of difference (RoD) in nucleosome occupancy between pluripotent and somatic cells. Surprisingly, most chromatin remains unchanged; a majority of rearrangements appear to affect a single nucleosome. RoDs are enriched at genes and regulatory elements, including enhancers associated with pluripotency and differentiation. RoDs co-localize with binding sites of key developmental regulators, including the reprogramming factors Klf4, Oct4/Sox2 and c-Myc. Nucleosomal landscapes in ESC enhancers are extensively altered, exhibiting lower nucleosome occupancy in pluripotent cells than in somatic cells. Most changes are reset during reprogramming. We conclude that changes in nucleosome occupancy are a hallmark of cell differentiation and reprogramming and likely identify regulatory regions essential for these processes. Changes in chromatin structure impact gene expression programs by modulating accessibility to the transcription machinery. Here, West et al. explore differences in nucleosome occupancy between mammalian pluripotent and somatic cells and uncover regulatory regions likely to play key roles in determining cell identity.
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Affiliation(s)
- Jason A West
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA [3] [4]
| | - April Cook
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA [3]
| | - Burak H Alver
- Center for Biomedical Informatics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Matthias Stadtfeld
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine, The Skirball Institute of Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA
| | - Aimee M Deaton
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Konrad Hochedlinger
- 1] Howard Hughes Medical Institute and the Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] The Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Peter J Park
- Center for Biomedical Informatics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Michael Y Tolstorukov
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2]
| | - Robert E Kingston
- 1] Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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62
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Sansoni V, Casas-Delucchi CS, Rajan M, Schmidt A, Bönisch C, Thomae AW, Staege MS, Hake SB, Cardoso MC, Imhof A. The histone variant H2A.Bbd is enriched at sites of DNA synthesis. Nucleic Acids Res 2014; 42:6405-20. [PMID: 24753410 PMCID: PMC4041467 DOI: 10.1093/nar/gku303] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 03/28/2014] [Accepted: 03/31/2014] [Indexed: 01/04/2023] Open
Abstract
Histone variants play an important role in shaping the mammalian epigenome and their aberrant expression is frequently observed in several types of cancer. However, the mechanisms that mediate their function and the composition of the variant-containing chromatin are still largely unknown. A proteomic interrogation of chromatin containing the different H2A variants macroH2A.1.2, H2A.Bbd and H2A revealed a strikingly different protein composition. Gene ontology analysis reveals a strong enrichment of splicing factors as well as components of the mammalian replisome in H2A.Bbd-containing chromatin. We find H2A.Bbd localizing transiently to sites of DNA synthesis during S-phase and during DNA repair. Cells that express H2A.Bbd have a shortened S-phase and are more susceptible to DNA damage, two phenotypes that are also observed in human Hodgkin's lymphoma cells that aberrantly express this variant. Based on our experiments we conclude that H2A.Bbd is targeted to newly synthesized DNA during replication and DNA repair. The transient incorporation of H2A.Bbd may be due to the intrinsic instability of nucleosomes carrying this variant or a faster chromatin loading. This potentially leads to a disturbance of the existing chromatin structure, which may have effects on cell cycle regulation and DNA damage sensitivity.
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Affiliation(s)
- Viola Sansoni
- Munich Center of Integrated Protein Science, Ludwig Maximilians University of Munich, 80336 Munich, Germany
| | | | - Malini Rajan
- Technische Universität Darmstadt Schnittspahnstr. 10, 64287 Darmstadt, Germany
| | - Andreas Schmidt
- Munich Center of Integrated Protein Science, Ludwig Maximilians University of Munich, 80336 Munich, Germany
| | - Clemens Bönisch
- Adolf-Butenandt Institute, Ludwig Maximilians University of Munich, 80336 Munich, Germany
| | - Andreas W Thomae
- Munich Center of Integrated Protein Science, Ludwig Maximilians University of Munich, 80336 Munich, Germany
| | - Martin S Staege
- Department of Pediatrics, Martin Luther University Halle-Wittenberg, Ernst-Grube-Str. 40, 06097 Halle, Germany
| | - Sandra B Hake
- Munich Center of Integrated Protein Science, Ludwig Maximilians University of Munich, 80336 Munich, Germany Adolf-Butenandt Institute, Ludwig Maximilians University of Munich, 80336 Munich, Germany
| | - M Cristina Cardoso
- Technische Universität Darmstadt Schnittspahnstr. 10, 64287 Darmstadt, Germany
| | - Axel Imhof
- Munich Center of Integrated Protein Science, Ludwig Maximilians University of Munich, 80336 Munich, Germany Adolf-Butenandt Institute, Ludwig Maximilians University of Munich, 80336 Munich, Germany
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63
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Abstract
Eukaryotic gene regulation involves a balance between packaging of the genome into nucleosomes and enabling access to regulatory proteins and RNA polymerase. Nucleosomes, consisting of DNA wrapped around a core of histone proteins, are integral components of gene regulation that restrict access to both regulatory sequences and the underlying template. In this review, Weber and Henikoff consider how histone variants and their interacting partners are involved in transcriptional regulation through the creation of unique chromatin states. Eukaryotic gene regulation involves a balance between packaging of the genome into nucleosomes and enabling access to regulatory proteins and RNA polymerase. Nucleosomes are integral components of gene regulation that restrict access to both regulatory sequences and the underlying template. Whereas canonical histones package the newly replicated genome, they can be replaced with histone variants that alter nucleosome structure, stability, dynamics, and, ultimately, DNA accessibility. Here we consider how histone variants and their interacting partners are involved in transcriptional regulation through the creation of unique chromatin states.
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Affiliation(s)
- Christopher M Weber
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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64
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Soboleva TA, Nekrasov M, Ryan DP, Tremethick DJ. Histone variants at the transcription start-site. Trends Genet 2014; 30:199-209. [DOI: 10.1016/j.tig.2014.03.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 03/23/2014] [Accepted: 03/24/2014] [Indexed: 01/30/2023]
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65
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Genome-wide analysis of the chromatin composition of histone H2A and H3 variants in mouse embryonic stem cells. PLoS One 2014; 9:e92689. [PMID: 24658136 PMCID: PMC3962432 DOI: 10.1371/journal.pone.0092689] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 02/24/2014] [Indexed: 12/31/2022] Open
Abstract
Genome-wide distribution of the majority of H2A and H3 variants (H2A, H2AX, H2AZ, macroH2A, H3.1, H3.2 and H3.3) was simultaneously investigated in mouse embryonic stem cells by chromatin immunoprecipitation sequencing. Around the transcription start site, histone variant distribution differed between genes possessing promoters of high and low CpG density, regardless of their expression levels. In the intergenic regions, regulatory elements were enriched in H2A.Z and H3.3, whereas repeat elements were abundant in H2A and macroH2A, and H3.1, respectively. Analysis of H2A and H3 variant combinations composing nucleosomes revealed that the H2A.Z and H3.3 combinations were present at a higher frequency throughout the genome than the other combinations, suggesting that H2A.Z and H3.3 associate preferentially with each other to comprise the nucleosomes independently of genome region. Finally, we found that chromatin was unstable only in regions where it was enriched in both H2A.Z and H3.3, but strongly quantified stable in regions in which only H3.3 was abundant. Therefore, histone variant composition is an important determinant of chromatin structure, which is associated with specific genomic functions.
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66
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Every amino acid matters: essential contributions of histone variants to mammalian development and disease. Nat Rev Genet 2014; 15:259-71. [PMID: 24614311 DOI: 10.1038/nrg3673] [Citation(s) in RCA: 233] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Despite a conserved role for histones as general DNA packaging agents, it is now clear that another key function of these proteins is to confer variations in chromatin structure to ensure dynamic patterns of transcriptional regulation in eukaryotes. The incorporation of histone variants is particularly important to this process. Recent knockdown and knockout studies in various cellular systems, as well as direct mutational evidence from human cancers, now suggest a crucial role for histone variant regulation in processes as diverse as differentiation and proliferation, meiosis and nuclear reprogramming. In this Review, we provide an overview of histone variants in the context of their unique functions during mammalian germ cell and embryonic development, and examine the consequences of aberrant histone variant regulation in human disease.
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67
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Goshima T, Shimada M, Sharif J, Matsuo H, Misaki T, Johmura Y, Murata K, Koseki H, Nakanishi M. Mammal-specific H2A variant, H2ABbd, is involved in apoptotic induction via activation of NF-κB signaling pathway. J Biol Chem 2014; 289:11656-11666. [PMID: 24584930 DOI: 10.1074/jbc.m113.541664] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Histone variants play specific roles in maintenance and regulation of chromatin structures. H2ABbd, an H2A variant, possesses a highly divergent structure compared with canonical H2A and is highly expressed in postmeiotic germ cells, but its functions in the regulation of gene expression are largely unknown. In the present study, we investigated the cellular phenotype associated with enforced H2ABbd expression. Among H2A variants, H2ABbd specifically caused growth defect in human cells and induced apoptosis. H2ABbd expression resulted in degradation of inhibitor of κB-α and translocation of NF-κB into nuclei, indicating the activation of NF-κB. Intriguingly, NF-κB activity was essential for H2ABbd-induced apoptosis. H2ABbd overexpression resulted in DNA damage after release from G1/S, progressed through the S phase slowly, and induced apoptosis. Furthermore, gene expression microarray analysis revealed that expression of H2ABbd activates groups of genes involved in apoptosis and postmeiotic germ cell development, suggesting that H2ABbd might influence transcription. Taken together, our data suggest that H2ABbd may contribute to specific chromatin structures and promote NF-κB activation, which could in turn induce apoptosis in mammalian cells.
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Affiliation(s)
- Takahiro Goshima
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Midori Shimada
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.
| | - Jafar Sharif
- Development Genetics Group, RIKEN Center for Integrative Medical Sciences (IMS), 1-7-22 Suehiuro-cho, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Hiromi Matsuo
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Toshinori Misaki
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Yoshikazu Johmura
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Kazuhiro Murata
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Haruhiko Koseki
- Development Genetics Group, RIKEN Center for Integrative Medical Sciences (IMS), 1-7-22 Suehiuro-cho, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Makoto Nakanishi
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.
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Chen Y, Chen Q, McEachin RC, Cavalcoli JD, Yu X. H2A.B facilitates transcription elongation at methylated CpG loci. Genome Res 2014; 24:570-9. [PMID: 24402521 PMCID: PMC3975057 DOI: 10.1101/gr.156877.113] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
H2A.B is a unique histone H2A variant that only exists in mammals. Here we found that H2A.B is ubiquitously expressed in major organs. Genome-wide analysis of H2A.B in mouse ES cells shows that H2A.B is associated with methylated DNA in gene body regions. Moreover, H2A.B-enriched gene loci are actively transcribed. One typical example is that H2A.B is enriched in a set of differentially methylated regions at imprinted loci and facilitates transcription elongation. These results suggest that H2A.B positively regulates transcription elongation by overcoming DNA methylation in the transcribed region. It provides a novel mechanism by which transcription is regulated at DNA hypermethylated regions.
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Affiliation(s)
- Yibin Chen
- Division of Molecular Medicine and Genetics, Department of Internal Medicine
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69
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Cong R, Das S, Douet J, Wong J, Buschbeck M, Mongelard F, Bouvet P. macroH2A1 histone variant represses rDNA transcription. Nucleic Acids Res 2014; 42:181-92. [PMID: 24071584 PMCID: PMC3874179 DOI: 10.1093/nar/gkt863] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 08/30/2013] [Accepted: 09/04/2013] [Indexed: 01/21/2023] Open
Abstract
The regulation of ribosomal DNA transcription is an important step for the control of cell growth. Epigenetic marks such as DNA methylation and posttranslational modifications of canonical histones have been involved in this regulation, but much less is known about the role of histone variants. In this work, we show that the histone variant macroH2A1 is present on the promoter of methylated rDNA genes. The inhibition of the expression of macroH2A1 in human HeLa and HepG2 cells and in a mouse ES cell line resulted in an up to 5-fold increase of pre-rRNA levels. This increased accumulation of pre-rRNA is accompanied by an increase of the loading of RNA polymerase I and UBF on the rDNA without any changes in the number of active rDNA genes. The inhibition of RNA polymerase I transcription by actinomycin D or by knocking down nucleolin, induces the recruitment of macroH2A1 on the rDNA and the relocalization of macroH2A1 in the nucleolus. Interestingly, the inhibition of rDNA transcription induced by nucleolin depletion is alleviated by the inactivation of macroH2A1. These results demonstrate that macroH2A1 is a new factor involved in the regulation of rDNA transcription.
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Affiliation(s)
- Rong Cong
- Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS USR 3010, Laboratoire Joliot-Curie, 69364 Lyon, France, The Institute of Predictive and Personalized Medicine of Cancer (IMPPC), 08916 Badalona, Barcelona, Spain and The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Sadhan Das
- Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS USR 3010, Laboratoire Joliot-Curie, 69364 Lyon, France, The Institute of Predictive and Personalized Medicine of Cancer (IMPPC), 08916 Badalona, Barcelona, Spain and The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Julien Douet
- Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS USR 3010, Laboratoire Joliot-Curie, 69364 Lyon, France, The Institute of Predictive and Personalized Medicine of Cancer (IMPPC), 08916 Badalona, Barcelona, Spain and The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Jiemin Wong
- Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS USR 3010, Laboratoire Joliot-Curie, 69364 Lyon, France, The Institute of Predictive and Personalized Medicine of Cancer (IMPPC), 08916 Badalona, Barcelona, Spain and The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Marcus Buschbeck
- Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS USR 3010, Laboratoire Joliot-Curie, 69364 Lyon, France, The Institute of Predictive and Personalized Medicine of Cancer (IMPPC), 08916 Badalona, Barcelona, Spain and The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Fabien Mongelard
- Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS USR 3010, Laboratoire Joliot-Curie, 69364 Lyon, France, The Institute of Predictive and Personalized Medicine of Cancer (IMPPC), 08916 Badalona, Barcelona, Spain and The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Philippe Bouvet
- Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS USR 3010, Laboratoire Joliot-Curie, 69364 Lyon, France, The Institute of Predictive and Personalized Medicine of Cancer (IMPPC), 08916 Badalona, Barcelona, Spain and The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
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70
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Abstract
In the past several years, the relationship between chromatin structure and mRNA processing has been the source of significant investigation across diverse disciplines. Central to these efforts was an unanticipated nonrandom distribution of chromatin marks across transcribed regions of protein-coding genes. In addition to the presence of specific histone modifications at the 5' and 3' ends of genes, exonic DNA was demonstrated to present a distinct chromatin landscape relative to intronic DNA. As splicing in higher eukaryotes predominantly occurs co-transcriptionally, these studies raised the possibility that chromatin modifications may aid the spliceosome in the detection of exons amidst vast stretches of noncoding intronic sequences. Recent investigations have supported a direct role for chromatin in splicing regulation and have suggested an intriguing role for splicing in the establishment of chromatin modifications. Here we will summarize an accumulating body of data that begins to reveal extensive coupling between chromatin structure and pre-mRNA splicing.
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Affiliation(s)
- Nazmul Haque
- Laboratory of Ribonucleoprotein Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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71
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Arimura Y, Kimura H, Oda T, Sato K, Osakabe A, Tachiwana H, Sato Y, Kinugasa Y, Ikura T, Sugiyama M, Sato M, Kurumizaka H. Structural basis of a nucleosome containing histone H2A.B/H2A.Bbd that transiently associates with reorganized chromatin. Sci Rep 2013; 3:3510. [PMID: 24336483 PMCID: PMC3863819 DOI: 10.1038/srep03510] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 11/29/2013] [Indexed: 01/26/2023] Open
Abstract
Human histone H2A.B (formerly H2A.Bbd), a non-allelic H2A variant, exchanges rapidly as compared to canonical H2A, and preferentially associates with actively transcribed genes. We found that H2A.B transiently accumulated at DNA replication and repair foci in living cells. To explore the biochemical function of H2A.B, we performed nucleosome reconstitution analyses using various lengths of DNA. Two types of H2A.B nucleosomes, octasome and hexasome, were formed with 116, 124, or 130 base pairs (bp) of DNA, and only the octasome was formed with 136 or 146 bp DNA. In contrast, only hexasome formation was observed by canonical H2A with 116 or 124 bp DNA. A small-angle X-ray scattering analysis revealed that the H2A.B octasome is more extended, due to the flexible detachment of the DNA regions at the entry/exit sites from the histone surface. These results suggested that H2A.B rapidly and transiently forms nucleosomes with short DNA segments during chromatin reorganization.
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Affiliation(s)
- Yasuhiro Arimura
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Hiroshi Kimura
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
- JST, CREST, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Takashi Oda
- Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan
| | - Koichi Sato
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Akihisa Osakabe
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Hiroaki Tachiwana
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yuko Sato
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
- JST, CREST, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yasuha Kinugasa
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tsuyoshi Ikura
- Department of Mutagenesis, Division of Chromatin Regulatory Network, Radiation Biology Center, Kyoto University, Yoshidakonoe, Sakyo-ku, Kyoto 606-8501, Japan
| | - Masaaki Sugiyama
- Research Reactor Institute, Kyoto University, Kumatori, Osaka, 590-0494, Japan
| | - Mamoru Sato
- Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan
- RIKEN SPring-8 Center, 1-1-1 koto, Sayo, Hyogo 679-5148, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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72
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Nekrasov M, Soboleva TA, Jack C, Tremethick DJ. Histone variant selectivity at the transcription start site: H2A.Z or H2A.Lap1. Nucleus 2013; 4:431-8. [PMID: 24213378 PMCID: PMC3925687 DOI: 10.4161/nucl.26862] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Considerable attention has been given to the understanding of how nucleosomes are altered or removed from the transcription start site of RNA polymerase II genes to enable transcription to proceed. This has led to the view that for transcriptional activation to occur, the transcription start site (TSS) must become depleted of nucleosomes. However, we have shown that this is not the case with different unstable histone H2A variant-containing nucleosomes occupying the TSS under different physiological settings. For example, during mouse spermatogenesis we found that the mouse homolog of human H2A.Bbd, H2A.Lap1, is targeted to the TSS of active genes expressed during specific stages of spermatogenesis. On the other hand, we observed in trophoblast stem cells, a H2A.Z-containing nucleosome occupying the TSS of genes active in the G1 phase of the cell cycle. Notably, this H2A.Z-containing nucleosome was different compared with other promoter specific H2A.Z nucleosomes by being heterotypic rather than being homotypic. In other words, it did not contain the expected two copies of H2A.Z per nucleosome but only one (i.e., H2A.Z/H2A rather than H2A.Z/H2A.Z). Given these observations, we wondered whether the histone variant composition of a nucleosome at an active TSS could in fact vary in the same cell type. To investigate this possibility, we performed H2A.Z ChIP-H2A reChIP assays in the mouse testis and compared this data with our testis H2A.Lap1 ChIP-seq data. Indeed, we find that different promoters involved in the expression of genes involved in distinct biological processes can contain either H2A.Z/H2A or H2A.Lap1. This argues that specific mechanisms exist, which can determine whether H2A.Z or H2A.Lap1 is targeted to the TSS of an active gene.
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Affiliation(s)
- Maxim Nekrasov
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
| | - Tatiana A Soboleva
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
| | - Cameron Jack
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
| | - David J Tremethick
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
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73
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Reddy AS, Marquez Y, Kalyna M, Barta A. Complexity of the alternative splicing landscape in plants. THE PLANT CELL 2013; 25:3657-83. [PMID: 24179125 PMCID: PMC3877793 DOI: 10.1105/tpc.113.117523] [Citation(s) in RCA: 516] [Impact Index Per Article: 46.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Revised: 09/27/2013] [Accepted: 10/08/2013] [Indexed: 05/18/2023]
Abstract
Alternative splicing (AS) of precursor mRNAs (pre-mRNAs) from multiexon genes allows organisms to increase their coding potential and regulate gene expression through multiple mechanisms. Recent transcriptome-wide analysis of AS using RNA sequencing has revealed that AS is highly pervasive in plants. Pre-mRNAs from over 60% of intron-containing genes undergo AS to produce a vast repertoire of mRNA isoforms. The functions of most splice variants are unknown. However, emerging evidence indicates that splice variants increase the functional diversity of proteins. Furthermore, AS is coupled to transcript stability and translation through nonsense-mediated decay and microRNA-mediated gene regulation. Widespread changes in AS in response to developmental cues and stresses suggest a role for regulated splicing in plant development and stress responses. Here, we review recent progress in uncovering the extent and complexity of the AS landscape in plants, its regulation, and the roles of AS in gene regulation. The prevalence of AS in plants has raised many new questions that require additional studies. New tools based on recent technological advances are allowing genome-wide analysis of RNA elements in transcripts and of chromatin modifications that regulate AS. Application of these tools in plants will provide significant new insights into AS regulation and crosstalk between AS and other layers of gene regulation.
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Affiliation(s)
- Anireddy S.N. Reddy
- Department of Biology, Program in Molecular Plant Biology, Program in Cell and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
- Address correspondence to
| | - Yamile Marquez
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna A-1030, Austria
| | - Maria Kalyna
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna A-1030, Austria
| | - Andrea Barta
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna A-1030, Austria
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74
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Li G, Zhou L. Genome-wide identification of chromatin transitional regions reveals diverse mechanisms defining the boundary of facultative heterochromatin. PLoS One 2013; 8:e67156. [PMID: 23840609 PMCID: PMC3696093 DOI: 10.1371/journal.pone.0067156] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 05/14/2013] [Indexed: 11/18/2022] Open
Abstract
Due to the self-propagating nature of the heterochromatic modification H3K27me3, chromatin barrier activities are required to demarcate the boundary and prevent it from encroaching into euchromatic regions. Studies in Drosophila and vertebrate systems have revealed several important chromatin barrier elements and their respective binding factors. However, epigenomic data indicate that the binding of these factors are not exclusive to chromatin boundaries. To gain a comprehensive understanding of facultative heterochromatin boundaries, we developed a two-tiered method to identify the Chromatin Transitional Region (CTR), i.e. the nucleosomal region that shows the greatest transition rate of the H3K27me3 modification as revealed by ChIP-Seq. This approach was applied to identify CTRs in Drosophila S2 cells and human HeLa cells. Although many insulator proteins have been characterized in Drosophila, less than half of the CTRs in S2 cells are associated with known insulator proteins, indicating unknown mechanisms remain to be characterized. Our analysis also revealed that the peak binding of insulator proteins are usually 1–2 nucleosomes away from the CTR. Comparison of CTR-associated insulator protein binding sites vs. those in heterochromatic region revealed that boundary-associated binding sites are distinctively flanked by nucleosome destabilizing sequences, which correlates with significant decreased nucleosome density and increased binding intensities of co-factors. Interestingly, several subgroups of boundaries have enhanced H3.3 incorporation but reduced nucleosome turnover rate. Our genome-wide study reveals that diverse mechanisms are employed to define the boundaries of facultative heterochromatin. In both Drosophila and mammalian systems, only a small fraction of insulator protein binding sites co-localize with H3K27me3 boundaries. However, boundary-associated insulator binding sites are distinctively flanked by nucleosome destabilizing sequences, which correlates with significantly decreased nucleosome density and increased binding of co-factors.
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Affiliation(s)
- Guangyao Li
- Graduate Program in Genetics and Genomics, University of Florida Genetics Institute; Department of Molecular Genetics and Microbiology & University of Florida Shands Cancer Center, College of Medicine, University of Florida. Gainesville, Florida, United States of America
| | - Lei Zhou
- Graduate Program in Genetics and Genomics, University of Florida Genetics Institute; Department of Molecular Genetics and Microbiology & University of Florida Shands Cancer Center, College of Medicine, University of Florida. Gainesville, Florida, United States of America
- * E-mail:
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75
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Terweij M, van Leeuwen F. Histone exchange: sculpting the epigenome. FRONTIERS IN LIFE SCIENCE 2013. [DOI: 10.1080/21553769.2013.838193] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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76
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Abstract
Precursor mRNA splicing is one of the most highly regulated processes in metazoan species. In addition to generating vast repertoires of RNAs and proteins, splicing has a profound impact on other gene regulatory layers, including mRNA transcription, turnover, transport, and translation. Conversely, factors regulating chromatin and transcription complexes impact the splicing process. This extensive crosstalk between gene regulatory layers takes advantage of dynamic spatial, physical, and temporal organizational properties of the cell nucleus, and further emphasizes the importance of developing a multidimensional understanding of splicing control.
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77
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Abstract
Chromatin acts as an organizer and indexer of genomic DNA and is a highly dynamic and regulated structure with properties directly related to its constituent parts. Histone variants are abundant components of chromatin that replace canonical histones in a subset of nucleosomes, thereby altering nucleosomal characteristics. The present review focuses on the H2A variant histones, summarizing current knowledge of how H2A variants can introduce chemical and functional heterogeneity into chromatin, the positions that nucleosomes containing H2A variants occupy in eukaryotic genomes, and the regulation of these localization patterns.
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78
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Combined micrococcal nuclease and exonuclease III digestion reveals precise positions of the nucleosome core/linker junctions: implications for high-resolution nucleosome mapping. J Mol Biol 2013; 425:1946-1960. [PMID: 23458408 DOI: 10.1016/j.jmb.2013.02.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 01/29/2013] [Accepted: 02/22/2013] [Indexed: 11/20/2022]
Abstract
Micrococcal nuclease (MNase) is extensively used in genome-wide mapping of nucleosomes but its preference for AT-rich DNA leads to errors in establishing precise positions of nucleosomes. Here, we show that the MNase digestion of nucleosomes assembled on a strong nucleosome positioning sequence, Widom's clone 601, releases nucleosome cores whose sizes are strongly affected by the linker DNA sequence. Our experiments produced nucleosomal DNA sizes varying between 147 and 155 bp, with positions of the MNase cuts reflecting positions of the A⋅T pairs rather than the nucleosome core/linker junctions determined by X-ray crystallography. Extent of chromatosomal DNA protection by linker histone H1 also depends on the linker DNA sequence. Remarkably, we found that a combined treatment with MNase and exonuclease III (exoIII) overcomes MNase sequence preference producing nucleosomal DNA trimmed symmetrically and precisely at the core/linker junctions regardless of the underlying DNA sequence. We propose that combined MNase/exoIII digestion can be applied to in situ chromatin for unbiased genome-wide mapping of nucleosome positions that is not influenced by DNA sequences at the core/linker junctions. The same approach can be also used for the precise mapping of the extent of linker DNA protection by H1 and other protein factors associated with nucleosome linkers.
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79
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Ioudinkova ES, Barat A, Pichugin A, Markova E, Sklyar I, Pirozhkova I, Robin C, Lipinski M, Ogryzko V, Vassetzky YS, Razin SV. Distinct distribution of ectopically expressed histone variants H2A.Bbd and MacroH2A in open and closed chromatin domains. PLoS One 2012; 7:e47157. [PMID: 23118866 PMCID: PMC3484066 DOI: 10.1371/journal.pone.0047157] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 09/13/2012] [Indexed: 12/12/2022] Open
Abstract
Background It becomes increasingly evident that nuclesomes are far from being identical to each other. This nucleosome diversity is due partially to the existence of histone variants encoded by separate genes. Among the known histone variants the less characterized are H2A.Bbd and different forms of macroH2A. This is especially true in the case of H2A.Bbd as there are still no commercially available antibodies specific to H2A.Bbd that can be used for chromatin immunoprecipitation (ChIP). Methods We have generated HeLa S3 cell lines stably expressing epitope-tagged versions of macroH2A1.1, H2A.Bbd or canonical H2A and analyzed genomic distribution of the tagged histones using ChIP-on-chip technique. Results The presence of histone H2A variants macroH2A1.1 and H2A.Bbd has been analyzed in the chromatin of several segments of human chromosomes 11, 16 and X that have been chosen for their different gene densities and chromatin status. Chromatin immunoprecipitation (ChIP) followed by hybridization with custom NimbleGene genomic microarrays demonstrated that in open chromatin domains containing tissue-specific along with housekeeping genes, the H2A.Bbd variant was preferentially associated with the body of a subset of transcribed genes. The macroH2A1.1 variant was virtually absent from some genes and underrepresented in others. In contrast, in closed chromatin domains which contain only tissue-specific genes inactive in HeLa S3 cells, both macroH2A1.1 and H2A.Bbd histone variants were present and often colocalized. Conclusions Genomic distribution of macro H2A and H2A.Bbd does not follow any simple rule and is drastically different in open and closed genomic domains.
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Affiliation(s)
- Elena S. Ioudinkova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Ana Barat
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- The Centre for Scientific Computing & Complex Systems Modelling (SCI-SYM), School of Computing, Dublin City University, Dublin, Ireland
| | - Andrey Pichugin
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Elena Markova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Ilya Sklyar
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Iryna Pirozhkova
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Chloe Robin
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Marc Lipinski
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Vasily Ogryzko
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
| | - Yegor S. Vassetzky
- CNRS UMR 8126, Univ. Paris-Sud 11, Institut de cancérologie Gustave Roussy, Villejuif, France
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
- * E-mail:
| | - Sergey V. Razin
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
- LIA1066, Laboratoire Franco-Russe de recherches en oncologie, Villejuif, France
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80
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Bönisch C, Hake SB. Histone H2A variants in nucleosomes and chromatin: more or less stable? Nucleic Acids Res 2012; 40:10719-41. [PMID: 23002134 PMCID: PMC3510494 DOI: 10.1093/nar/gks865] [Citation(s) in RCA: 210] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
In eukaryotes, DNA is organized together with histones and non-histone proteins into a highly complex nucleoprotein structure called chromatin, with the nucleosome as its monomeric subunit. Various interconnected mechanisms regulate DNA accessibility, including replacement of canonical histones with specialized histone variants. Histone variant incorporation can lead to profound chromatin structure alterations thereby influencing a multitude of biological processes ranging from transcriptional regulation to genome stability. Among core histones, the H2A family exhibits highest sequence divergence, resulting in the largest number of variants known. Strikingly, H2A variants differ mostly in their C-terminus, including the docking domain, strategically placed at the DNA entry/exit site and implicated in interactions with the (H3–H4)2-tetramer within the nucleosome and in the L1 loop, the interaction interface of H2A–H2B dimers. Moreover, the acidic patch, important for internucleosomal contacts and higher-order chromatin structure, is altered between different H2A variants. Consequently, H2A variant incorporation has the potential to strongly regulate DNA organization on several levels resulting in meaningful biological output. Here, we review experimental evidence pinpointing towards outstanding roles of these highly variable regions of H2A family members, docking domain, L1 loop and acidic patch, and close by discussing their influence on nucleosome and higher-order chromatin structure and stability.
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Affiliation(s)
- Clemens Bönisch
- Department of Molecular Biology, Center for Integrated Protein Science Munich, Adolf-Butenandt-Institute, Ludwig-Maximilians-University Munich, 80336 Munich, Germany.
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