1
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Jamge B, Lorković ZJ, Axelsson E, Osakabe A, Shukla V, Yelagandula R, Akimcheva S, Kuehn AL, Berger F. Histone variants shape chromatin states in Arabidopsis. eLife 2023; 12:RP87714. [PMID: 37467143 PMCID: PMC10393023 DOI: 10.7554/elife.87714] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023] Open
Abstract
How different intrinsic sequence variations and regulatory modifications of histones combine in nucleosomes remain unclear. To test the importance of histone variants in the organization of chromatin we investigated how histone variants and histone modifications assemble in the Arabidopsis thaliana genome. We showed that a limited number of chromatin states divide euchromatin and heterochromatin into several subdomains. We found that histone variants are as significant as histone modifications in determining the composition of chromatin states. Particularly strong associations were observed between H2A variants and specific combinations of histone modifications. To study the role of H2A variants in organizing chromatin states we determined the role of the chromatin remodeler DECREASED IN DNA METHYLATION (DDM1) in the organization of chromatin states. We showed that the loss of DDM1 prevented the exchange of the histone variant H2A.Z to H2A.W in constitutive heterochromatin, resulting in significant effects on the definition and distribution of chromatin states in and outside of constitutive heterochromatin. We thus propose that dynamic exchanges of histone variants control the organization of histone modifications into chromatin states, acting as molecular landmarks.
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Affiliation(s)
- Bhagyshree Jamge
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
- Vienna BioCenterViennaAustria
| | - Zdravko J Lorković
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
| | - Elin Axelsson
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
| | - Akihisa Osakabe
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-kuTokyoJapan
- PRESTO, Japan Science and Technology Agency, HonchoKawaguchiJapan
| | - Vikas Shukla
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
- Vienna BioCenterViennaAustria
| | - Ramesh Yelagandula
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
- Institute of Molecular Biotechnology, IMBA, Dr. Bohr-Gasse 3ViennaAustria
| | - Svetlana Akimcheva
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
| | - Annika Luisa Kuehn
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
| | - Frédéric Berger
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenterViennaAustria
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2
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The Role of Epigenetics in Brain and Spinal Cord Tumors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1394:119-136. [PMID: 36587385 DOI: 10.1007/978-3-031-14732-6_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Identification of distinct genetic and epigenetic profiles in various neuroepithelial tumors has improved the classification and uncovered novel diagnostic, prognostic, and predictive molecular biomarkers for improved prediction of treatment response and outcome. Especially, in pediatric high-grade brain tumors, such as diffuse midline glioma, H3K27M-altered and posterior fossa group A-ependymoma, epigenetic changes predominate, along with changes in expression of known oncogenes and tumor suppressor genes induced by histone modifications and DNA methylation. The precise role of epigenetic abnormalities is important for understanding tumorigenesis and the establishment of brain tumor treatment strategies. Using powerful epigenetic-based therapies for cancer cells, the aberrantly regulated epigenome can be restored to a more normal state through epigenetic reprogramming. Combinations of agents targeting DNA methylation and/or other epigenetic modifications may be a promising cancer treatment. Therefore, the integration of multi-omics data including epigenomics is now important for classifying primary brain tumors and predicting their biological behavior. Recent advances in molecular genetics and epigenetic integrated diagnostics of brain tumors influence new strategies for targeted therapy.
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3
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Kenworthy CA, Haque N, Liou SH, Chandris P, Wong V, Dziuba P, Lavis LD, Liu WL, Singer RH, Coleman RA. Bromodomains regulate dynamic targeting of the PBAF chromatin-remodeling complex to chromatin hubs. Biophys J 2022; 121:1738-1752. [PMID: 35364106 PMCID: PMC9117891 DOI: 10.1016/j.bpj.2022.03.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/20/2021] [Accepted: 03/24/2022] [Indexed: 11/12/2022] Open
Abstract
Chromatin remodelers actively target arrays of acetylated nucleosomes at select enhancers and promoters to facilitate or shut down the repeated recruitment of RNA polymerase II during transcriptional bursting. It is poorly understood how chromatin remodelers such as PBAF dynamically target different chromatin states inside a live cell. Our live-cell single-molecule fluorescence microscopy study reveals chromatin hubs throughout the nucleus where PBAF rapidly cycles on and off the genome. Deletion of PBAF's bromodomains impairs targeting and stable engagement of chromatin in hubs. Dual color imaging reveals that PBAF targets both euchromatic and heterochromatic hubs with distinct genome-binding kinetic profiles that mimic chromatin stability. Removal of PBAF's bromodomains stabilizes H3.3 binding within chromatin, indicating that bromodomains may play a direct role in remodeling of the nucleosome. Our data suggests that PBAF's dynamic bromodomain-mediated engagement of a nucleosome may reflect the chromatin-remodeling potential of differentially bound chromatin states.
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Affiliation(s)
- Charles A Kenworthy
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York
| | - Nayem Haque
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York
| | - Shu-Hao Liou
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York
| | - Panagiotis Chandris
- Section on High Resolution Optical Imaging, National Institute on Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland
| | - Vincent Wong
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York
| | - Patrycja Dziuba
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York
| | - Luke D Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia
| | - Wei-Li Liu
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York
| | - Robert H Singer
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York; Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia
| | - Robert A Coleman
- Gruss-Lipper Biophotonics Center, Department of Cell Biology, Albert Einstein College of Medicine, New York.
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4
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Vacík T, Lađinović D, Raška I. KDM2A/B lysine demethylases and their alternative isoforms in development and disease. Nucleus 2019; 9:431-441. [PMID: 30059280 PMCID: PMC7000146 DOI: 10.1080/19491034.2018.1498707] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Aberrant levels of histone modifications lead to chromatin malfunctioning and consequently to various developmental defects and human diseases. Therefore, the proteins bearing the ability to modify histones have been extensively studied and the molecular mechanisms of their action are now fairly well understood. However, little attention has been paid to naturally occurring alternative isoforms of chromatin modifying proteins and to their biological roles. In this review, we focus on mammalian KDM2A and KDM2B, the only two lysine demethylases whose genes have been described to produce also an alternative isoform lacking the N-terminal demethylase domain. These short KDM2A/B-SF isoforms arise through alternative promoter usage and seem to play important roles in development and disease. We hypothesise about the biological significance of these alternative isoforms, which might represent a more common evolutionarily conserved regulatory mechanism.
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Affiliation(s)
- Tomáš Vacík
- a Institute of Biology and Medical Genetics, First Faculty of Medicine , Charles University and General University Hospital in Prague , Praha 2 , Czech Republic
| | - Dijana Lađinović
- a Institute of Biology and Medical Genetics, First Faculty of Medicine , Charles University and General University Hospital in Prague , Praha 2 , Czech Republic
| | - Ivan Raška
- a Institute of Biology and Medical Genetics, First Faculty of Medicine , Charles University and General University Hospital in Prague , Praha 2 , Czech Republic
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5
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Kraushaar DC, Chen Z, Tang Q, Cui K, Zhang J, Zhao K. The gene repressor complex NuRD interacts with the histone variant H3.3 at promoters of active genes. Genome Res 2018; 28:1646-1655. [PMID: 30254051 PMCID: PMC6211640 DOI: 10.1101/gr.236224.118] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 09/13/2018] [Indexed: 12/13/2022]
Abstract
The histone variant H3.3 is deposited across active genes, regulatory regions, and telomeres. It remains unclear how H3.3 interacts with chromatin modifying enzymes and thereby modulates gene activity. In this study, we performed a co-immunoprecipitation-mass spectrometry analysis of proteins associated with H3.3-containing nucleosomes and identified the nucleosome remodeling and deacetylase complex (NuRD) as a major H3.3-interactor. We show that the H3.3-NuRD interaction is dependent on the H3.3 lysine 4 residue and that NuRD binding occurs when lysine 4 is in its unmodified state. The majority of NuRD binding colocalizes with H3.3 and directly correlates with gene activity. H3.3 depletion led to reduced levels of NuRD at sites previously occupied by H3.3, as well as a global decrease in histone marks associated with gene activation. Our results demonstrate the importance of H3.3 in the maintenance of the cellular epigenetic landscape and reveal a highly prevalent interaction between the histone variant H3.3 and the multiprotein complex NuRD.
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Affiliation(s)
- Daniel C Kraushaar
- Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Zuozhou Chen
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology; National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China
| | - Qingsong Tang
- Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Kairong Cui
- Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Junfang Zhang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology; National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China
| | - Keji Zhao
- Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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6
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Kong Q, Banaszynski LA, Geng F, Zhang X, Zhang J, Zhang H, O'Neill CL, Yan P, Liu Z, Shido K, Palermo GD, Allis CD, Rafii S, Rosenwaks Z, Wen D. Histone variant H3.3-mediated chromatin remodeling is essential for paternal genome activation in mouse preimplantation embryos. J Biol Chem 2018; 293:3829-3838. [PMID: 29358330 DOI: 10.1074/jbc.ra117.001150] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/02/2018] [Indexed: 12/22/2022] Open
Abstract
Derepression of chromatin-mediated transcriptional repression of paternal and maternal genomes is considered the first major step that initiates zygotic gene expression after fertilization. The histone variant H3.3 is present in both male and female gametes and is thought to be important for remodeling the paternal and maternal genomes for activation during both fertilization and embryogenesis. However, the underlying mechanisms remain poorly understood. Using our H3.3B-HA-tagged mouse model, engineered to report H3.3 expression in live animals and to distinguish different sources of H3.3 protein in embryos, we show here that sperm-derived H3.3 (sH3.3) protein is removed from the sperm genome shortly after fertilization and extruded from the zygotes via the second polar bodies (PBII) during embryogenesis. We also found that the maternal H3.3 (mH3.3) protein is incorporated into the paternal genome as early as 2 h postfertilization and is detectable in the paternal genome until the morula stage. Knockdown of maternal H3.3 resulted in compromised embryonic development both of fertilized embryos and of androgenetic haploid embryos. Furthermore, we report that mH3.3 depletion in oocytes impairs both activation of the Oct4 pluripotency marker gene and global de novo transcription from the paternal genome important for early embryonic development. Our results suggest that H3.3-mediated paternal chromatin remodeling is essential for the development of preimplantation embryos and the activation of the paternal genome during embryogenesis.
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Affiliation(s)
- Qingran Kong
- From the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine and.,Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin 150030, China, and
| | - Laura A Banaszynski
- Laboratory of Chromatin Biology and Epigenetics, Rockefeller University, New York, New York 10065
| | - Fuqiang Geng
- Department of Medicine, Weill Cornell Medical College, New York, New York 10065
| | - Xiaolei Zhang
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin 150030, China, and
| | - Jiaming Zhang
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin 150030, China, and
| | - Heng Zhang
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin 150030, China, and
| | - Claire L O'Neill
- From the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine and
| | - Peidong Yan
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin 150030, China, and
| | - Zhonghua Liu
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin 150030, China, and
| | - Koji Shido
- Department of Medicine, Weill Cornell Medical College, New York, New York 10065
| | - Gianpiero D Palermo
- From the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine and
| | - C David Allis
- Laboratory of Chromatin Biology and Epigenetics, Rockefeller University, New York, New York 10065
| | - Shahin Rafii
- Department of Medicine, Weill Cornell Medical College, New York, New York 10065
| | - Zev Rosenwaks
- From the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine and
| | - Duancheng Wen
- From the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine and
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7
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García-Giménez JL, Romá-Mateo C, Pérez-Machado G, Peiró-Chova L, Pallardó FV. Role of glutathione in the regulation of epigenetic mechanisms in disease. Free Radic Biol Med 2017; 112:36-48. [PMID: 28705657 DOI: 10.1016/j.freeradbiomed.2017.07.008] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/29/2017] [Accepted: 07/06/2017] [Indexed: 12/14/2022]
Abstract
Epigenetics is a rapidly growing field that studies gene expression modifications not involving changes in the DNA sequence. Histone H3, one of the basic proteins in the nucleosomes that make up chromatin, is S-glutathionylated in mammalian cells and tissues, making Gamma-L-glutamyl-L-cysteinylglycine, glutathione (GSH), a physiological antioxidant and second messenger in cells, a new post-translational modifier of the histone code that alters the structure of the nucleosome. However, the role of GSH in the epigenetic mechanisms likely goes beyond a mere structural function. Evidence supports the hypothesis that there is a link between GSH metabolism and the control of epigenetic mechanisms at different levels (i.e., substrate availability, enzymatic activity for DNA methylation, changes in the expression of microRNAs, and participation in the histone code). However, little is known about the molecular pathways by which GSH can control epigenetic events. Studying mutations in enzymes involved in GSH metabolism and the alterations of the levels of cofactors affecting epigenetic mechanisms appears challenging. However, the number of diseases induced by aberrant epigenetic regulation is growing, so elucidating the intricate network between GSH metabolism, oxidative stress and epigenetics could shed light on how their deregulation contributes to the development of neurodegeneration, cancer, metabolic pathologies and many other types of diseases.
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Affiliation(s)
- José Luis García-Giménez
- Center for Biomedical Network Research on Rare Diseases (CIBERER) Institute of Health Carlos III, Valencia, Spain; Mixed Unit INCLIVA-CIPF Research Institutes, Valencia, Spain; Dept. Physiology, School of Medicine and Dentistry, Universitat de València (UV), Valencia, Spain; Epigenetics Research Platform (CIBERER/UV), Valencia, Spain.
| | - Carlos Romá-Mateo
- Center for Biomedical Network Research on Rare Diseases (CIBERER) Institute of Health Carlos III, Valencia, Spain; Mixed Unit INCLIVA-CIPF Research Institutes, Valencia, Spain; Dept. Physiology, School of Medicine and Dentistry, Universitat de València (UV), Valencia, Spain; Epigenetics Research Platform (CIBERER/UV), Valencia, Spain; Faculty of Biomedicine and Health Sciences, Universidad Europea de Valencia, Valencia, Spain
| | - Gisselle Pérez-Machado
- Dept. Physiology, School of Medicine and Dentistry, Universitat de València (UV), Valencia, Spain; Epigenetics Research Platform (CIBERER/UV), Valencia, Spain
| | | | - Federico V Pallardó
- Center for Biomedical Network Research on Rare Diseases (CIBERER) Institute of Health Carlos III, Valencia, Spain; Mixed Unit INCLIVA-CIPF Research Institutes, Valencia, Spain; Dept. Physiology, School of Medicine and Dentistry, Universitat de València (UV), Valencia, Spain; Epigenetics Research Platform (CIBERER/UV), Valencia, Spain.
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8
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The Drosophila DAXX-Like Protein (DLP) Cooperates with ASF1 for H3.3 Deposition and Heterochromatin Formation. Mol Cell Biol 2017; 37:MCB.00597-16. [PMID: 28320872 DOI: 10.1128/mcb.00597-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 03/09/2017] [Indexed: 01/22/2023] Open
Abstract
Histone variants are nonallelic isoforms of canonical histones, and they are deposited, in contrast to canonical histones, in a replication-independent (RI) manner. RI deposition of H3.3, a histone variant from the H3.3 family, is mediated in mammals by distinct pathways involving either the histone regulator A (HIRA) complex or the death-associated protein (DAXX)/α-thalassemia X-linked mental retardation protein (ATRX) complex. Here, we investigated the function of the Drosophila DAXX-like protein (DLP) by using both fly genetic approaches and protein biochemistry. DLP specifically interacts with H3.3 and shows a prominent localization on the base of the X chromosome, where it appears to act in concert with XNP, the Drosophila homolog of ATRX, in heterochromatin assembly and maintenance. The functional association between DLP and XNP is further supported by a series of experiments that illustrate genetic interactions and the DLP-XNP-dependent localization of specific chromosomal proteins. In addition, DLP both participates in the RI deposition of H3.3 and associates with anti-silencing factor 1 (ASF1). We suggest, in agreement with a recently proposed model, that DLP and ASF1 are part of a predeposition complex, which is recruited by XNP and is necessary to prevent DNA exposure in the nucleus.
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9
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Kannan M, Li J, Fritz SE, Husarek KE, Sanford JC, Sullivan TL, Tiwary PK, An W, Boeke JD, Symer DE. Dynamic silencing of somatic L1 retrotransposon insertions reflects the developmental and cellular contexts of their genomic integration. Mob DNA 2017; 8:8. [PMID: 28491150 PMCID: PMC5424313 DOI: 10.1186/s13100-017-0091-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 05/03/2017] [Indexed: 02/15/2023] Open
Abstract
Background The ongoing mobilization of mammalian transposable elements (TEs) contributes to natural genetic variation. To survey the epigenetic control and expression of reporter genes inserted by L1 retrotransposition in diverse cellular and genomic contexts, we engineered highly sensitive, real-time L1 retrotransposon reporter constructs. Results Here we describe different patterns of expression and epigenetic controls of newly inserted sequences retrotransposed by L1 in various somatic cells and tissues including cultured human cancer cells, mouse embryonic stem cells, and tissues of pseudofounder transgenic mice and their progeny. In cancer cell lines, the newly inserted sequences typically underwent rapid transcriptional gene silencing, but they lacked cytosine methylation even after many cell divisions. L1 reporter expression was reversible and oscillated frequently. Silenced or variegated reporter expression was strongly and uniformly reactivated by treatment with inhibitors of histone deacetylation, revealing the mechanism for their silencing. By contrast, de novo integrants retrotransposed by L1 in pluripotent mouse embryonic stem (ES) cells underwent rapid silencing by dense cytosine methylation. Similarly, de novo cytosine methylation also was identified at new integrants when studied in several distinct somatic tissues of adult founder mice. Pre-existing L1 elements in cultured human cancer cells were stably silenced by dense cytosine methylation, whereas their transcription modestly increased when cytosine methylation was experimentally reduced in cells lacking DNA methyltransferases DNMT1 and DNMT3b. As a control, reporter genes mobilized by piggyBac (PB), a DNA transposon, revealed relatively stable and robust expression without apparent silencing in both cultured cancer cells and ES cells. Conclusions We hypothesize that the de novo methylation marks at newly inserted sequences retrotransposed by L1 in early pre-implantation development are maintained or re-established in adult somatic tissues. By contrast, histone deacetylation reversibly silences L1 reporter insertions that had mobilized at later timepoints in somatic development and differentiation, e.g., in cancer cell lines. We conclude that the cellular contexts of L1 retrotransposition can determine expression or silencing of newly integrated sequences. We propose a model whereby reporter expression from somatic TE insertions reflects the timing, molecular mechanism, epigenetic controls and the genomic, cellular and developmental contexts of their integration. Electronic supplementary material The online version of this article (doi:10.1186/s13100-017-0091-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Manoj Kannan
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, Pilani, 333031 Rajasthan India.,Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Present Address: Birla Institute of Technology and Science, Pilani, Dubai campus, Dubai, United Arab Emirates
| | - Jingfeng Li
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH USA.,Department of Internal Medicine, The Ohio State University, Columbus, OH USA
| | - Sarah E Fritz
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD USA
| | - Kathryn E Husarek
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: Aventiv Research, Inc., Columbus, OH USA
| | - Jonathan C Sanford
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH USA.,Present Address: Drug Safety Research and Development, Pfizer, Inc., Groton, CT USA
| | - Teresa L Sullivan
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA
| | - Pawan Kumar Tiwary
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Present Address: Biocon, Bangalore, India
| | - Wenfeng An
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD USA.,Present Address: Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD USA
| | - Jef D Boeke
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD USA.,Present Address: Institute for Systems Genetics, New York University Langone Medical Center, New York, NY USA
| | - David E Symer
- Laboratory of Immunobiology, Mouse Cancer Genetics Program and Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702 USA.,Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH USA.,Human Cancer Genetics Program, and Department of Biomedical Informatics, The Ohio State University, Columbus, OH USA.,Human Cancer Genetics Program, Department of Cancer Biology and Genetics, and Department of Biomedical Informatics, The Ohio State University, Tzagournis Research Facility, Room 440, 420 West 12th Ave, Columbus, OH 43210 USA
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10
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Taguchi H, Xie Y, Horikoshi N, Maehara K, Harada A, Nogami J, Sato K, Arimura Y, Osakabe A, Kujirai T, Iwasaki T, Semba Y, Tachibana T, Kimura H, Ohkawa Y, Kurumizaka H. Crystal Structure and Characterization of Novel Human Histone H3 Variants, H3.6, H3.7, and H3.8. Biochemistry 2017; 56:2184-2196. [DOI: 10.1021/acs.biochem.6b01098] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hiroyuki Taguchi
- Laboratory of Structural
Biology,
Graduate School of Advanced Science and Engineering, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yan Xie
- Laboratory of Structural
Biology,
Graduate School of Advanced Science and Engineering, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Naoki Horikoshi
- Laboratory of Structural
Biology,
Graduate School of Advanced Science and Engineering, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Kazumitsu Maehara
- Division of Transcriptomics, Medical
Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi,
Higashi-ku, Fukuoka 812-8582, Japan
| | - Akihito Harada
- Division of Transcriptomics, Medical
Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi,
Higashi-ku, Fukuoka 812-8582, Japan
| | - Jumpei Nogami
- Division of Transcriptomics, Medical
Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi,
Higashi-ku, Fukuoka 812-8582, Japan
| | - Koichi Sato
- Laboratory of Structural
Biology,
Graduate School of Advanced Science and Engineering, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yasuhiro Arimura
- Laboratory of Structural
Biology,
Graduate School of Advanced Science and Engineering, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, 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, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Tomoya Kujirai
- Laboratory of Structural
Biology,
Graduate School of Advanced Science and Engineering, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Takeshi Iwasaki
- Division of Transcriptomics, Medical
Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi,
Higashi-ku, Fukuoka 812-8582, Japan
| | - Yuichiro Semba
- Division of Transcriptomics, Medical
Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi,
Higashi-ku, Fukuoka 812-8582, Japan
| | - Taro Tachibana
- Department of Bioengineering, Graduate
School of Engineering, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Hiroshi Kimura
- Cell Biology Unit,
Institute of
Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
| | - Yasuyuki Ohkawa
- Division of Transcriptomics, Medical
Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi,
Higashi-ku, Fukuoka 812-8582, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Structural
Biology,
Graduate School of Advanced Science and Engineering, Research Institute
for Science and Engineering, and Institute for Medical-oriented Structural
Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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11
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Kujirai T, Horikoshi N, Sato K, Maehara K, Machida S, Osakabe A, Kimura H, Ohkawa Y, Kurumizaka H. Structure and function of human histone H3.Y nucleosome. Nucleic Acids Res 2016; 44:6127-41. [PMID: 27016736 PMCID: PMC5291245 DOI: 10.1093/nar/gkw202] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 03/16/2016] [Indexed: 12/25/2022] Open
Abstract
Histone H3.Y is a primate-specific, distant H3 variant. It is evolutionarily derived from H3.3, and may function in transcription regulation. However, the mechanism by which H3.Y regulates transcription has not been elucidated. In the present study, we determined the crystal structure of the H3.Y nucleosome, and found that many H3.Y-specific residues are located on the entry/exit sites of the nucleosome. Biochemical analyses revealed that the DNA ends of the H3.Y nucleosome were more flexible than those of the H3.3 nucleosome, although the H3.Y nucleosome was stable in vitro and in vivo. Interestingly, the linker histone H1, which compacts nucleosomal DNA, appears to bind to the H3.Y nucleosome less efficiently, as compared to the H3.3 nucleosome. These characteristics of the H3.Y nucleosome are also conserved in the H3.Y/H3.3 heterotypic nucleosome, which may be the predominant form in cells. In human cells, H3.Y preferentially accumulated around transcription start sites (TSSs). Taken together, H3.Y-containing nucleosomes around transcription start sites may form relaxed chromatin that allows transcription factor access, to regulate the transcription status of specific genes.
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Affiliation(s)
- Tomoya Kujirai
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Naoki Horikoshi
- Research Institute for Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, 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
| | - Kazumitsu Maehara
- Division of Transcriptomics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Shinichi Machida
- 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
| | - Hiroshi Kimura
- Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Yasuyuki Ohkawa
- Division of Transcriptomics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, 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 Research Institute for Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan Institute for Medical-oriented Structural Biology, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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12
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Szyf M. Prospects for the development of epigenetic drugs for CNS conditions. Nat Rev Drug Discov 2015; 14:461-74. [DOI: 10.1038/nrd4580] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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Szyf M. Epigenetics, a key for unlocking complex CNS disorders? Therapeutic implications. Eur Neuropsychopharmacol 2015; 25:682-702. [PMID: 24857313 DOI: 10.1016/j.euroneuro.2014.01.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 12/07/2013] [Accepted: 01/11/2014] [Indexed: 12/13/2022]
Abstract
Aberrant changes in gene function are believed to be involved in a wide spectrum of human disease including behavioral, cognitive and neurodegenerative pathologies. Most of the attention in last few decades have focused on changes in gene sequence as a cause of gene dysfunction leading to disease and mental health disorders. Germ line mutations or other alterations in the sequence of DNA that associate with different behavioral and neurological pathologies have been identified. However, sequence alterations explain only a small fraction of the cases. In addition there is evidence for "gene-environment" interactions in the brain suggesting mechanisms that alter gene function and the phenotype through environmental exposure. Genes are programmed by "epigenetic" mechanisms such as chromatin structure, chromatin modification and DNA methylation. These mechanisms confer on similar sequences different identities during cellular differentiation. Epigenetic differences are proposed to be involved in differentiating gene function in response to different environmental contexts and could result in alterations in functional gene networks that lead to brain disease. Epigenetic markers could serve important biomarkers in brain and behavioral diseases. Moreover, epigenetic processes are potentially reversible pointing to epigenetic therapeutics in psychotherapy.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada H3G1Y5.
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14
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Epigenetic mechanisms of perinatal programming: translational approaches from rodent to human and back. ADVANCES IN NEUROBIOLOGY 2015; 10:363-80. [PMID: 25287549 DOI: 10.1007/978-1-4939-1372-5_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Perinatal life is a period of enhanced plasticity and susceptibility to environmental effects via the maternal environment or parental care. A variety of studies have indicated that epigenetic mechanisms, which can alter gene function without a change in gene sequence, play a role in setting developmental trajectories that impact health, including mental health. This chapter reviews examples of translational approaches to the study of biological embedding of mental health via differences in parental care.
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15
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Asymmetric distribution of histones during Drosophila male germline stem cell asymmetric divisions. Chromosome Res 2014; 21:255-69. [PMID: 23681658 DOI: 10.1007/s10577-013-9356-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
It has long been known that epigenetic changes are inheritable. However, except for DNA methylation, little is known about the molecular mechanisms of epigenetic inheritance. Many types of stem cells undergo asymmetric cell divisions to generate self-renewed stem cells and daughter cells committed for differentiation. Still, whether and how stem cells retain their epigenetic memory remain questions to be elucidated. During the asymmetric division of Drosophila male germline stem cell (GSC), our recent studies revealed that the preexisting histone 3 (H3) are selectively segregated to the GSC, whereas newly synthesized H3 deposited during DNA replication are enriched in the differentiating daughter cell. We propose a two-step model to explain this asymmetric histone distribution. First, prior to mitosis, preexisting histones and newly synthesized histones are differentially distributed at two sets of sister chromatids. Next, during mitosis, the set of sister chromatids that mainly consist of preexisting histones are segregated to GSCs, while the other set of sister chromatids enriched with newly synthesized histones are partitioned to the daughter cell committed for differentiation. In this review, we apply current knowledge about epigenetic inheritance and asymmetric cell division to inform our discussion of potential molecular mechanisms and the cellular basis underlying this asymmetric histone distribution pattern. We will also discuss whether this phenomenon contributes to the maintenance of stem cell identity and resetting chromatin structure in the other daughter cell for differentiation.
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16
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Dorighi KM, Tamkun JW. The trithorax group proteins Kismet and ASH1 promote H3K36 dimethylation to counteract Polycomb group repression in Drosophila. Development 2013; 140:4182-92. [PMID: 24004944 DOI: 10.1242/dev.095786] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Members of the Polycomb group of repressors and trithorax group of activators maintain heritable states of transcription by modifying nucleosomal histones or remodeling chromatin. Although tremendous progress has been made toward defining the biochemical activities of Polycomb and trithorax group proteins, much remains to be learned about how they interact with each other and the general transcription machinery to maintain on or off states of gene expression. The trithorax group protein Kismet (KIS) is related to the SWI/SNF and CHD families of chromatin remodeling factors. KIS promotes transcription elongation, facilitates the binding of the trithorax group histone methyltransferases ASH1 and TRX to active genes, and counteracts repressive methylation of histone H3 on lysine 27 (H3K27) by Polycomb group proteins. Here, we sought to clarify the mechanism of action of KIS and how it interacts with ASH1 to antagonize H3K27 methylation in Drosophila. We present evidence that KIS promotes transcription elongation and counteracts Polycomb group repression via distinct mechanisms. A chemical inhibitor of transcription elongation, DRB, had no effect on ASH1 recruitment or H3K27 methylation. Conversely, loss of ASH1 function had no effect on transcription elongation. Mutations in kis cause a global reduction in the di- and tri-methylation of histone H3 on lysine 36 (H3K36) - modifications that antagonize H3K27 methylation in vitro. Furthermore, loss of ASH1 significantly decreases H3K36 dimethylation, providing further evidence that ASH1 is an H3K36 dimethylase in vivo. These and other findings suggest that KIS antagonizes Polycomb group repression by facilitating ASH1-dependent H3K36 dimethylation.
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Affiliation(s)
- Kristel M Dorighi
- Department of Molecular Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA
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17
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Regulation of nucleosome dynamics by histone modifications. Nat Struct Mol Biol 2013; 20:259-66. [PMID: 23463310 DOI: 10.1038/nsmb.2470] [Citation(s) in RCA: 618] [Impact Index Per Article: 56.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 11/02/2012] [Indexed: 12/12/2022]
Abstract
Chromatin is a dynamic structure that must respond to myriad stimuli to regulate access to DNA, and chemical modification of histones is a major means by which the cell modulates nucleosome mobility and turnover. Histone modifications are linked to essentially every cellular process requiring DNA access, including transcription, replication and repair. Here we consider properties of the major types of histone modification in the context of their associated biological processes to view them in light of the cellular mechanisms that regulate nucleosome dynamics.
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18
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Epigenetics in fertilization and preimplantation embryo development. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2013; 113:423-32. [PMID: 23454467 DOI: 10.1016/j.pbiomolbio.2013.02.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Revised: 01/10/2013] [Accepted: 02/20/2013] [Indexed: 12/30/2022]
Abstract
Epigenetic reprogramming of the parental genomes upon fertilization is required for proper embryonic development. It has long been appreciated that asymmetric distribution of histone modifications as well as differences in the level of DNA methylation exist between the parental pronuclei in mammalian zygotes and during preimplantation development. The speed at which the paternal genome is demethylated after entering the oocyte and the fact that rapid demethylation occurs in the absence of DNA replication have led many to hypothesize that a DNA demethylase must exist. However, such an enzyme has not been found. That the genome of mammalian preimplantation embryos undergo a wave of global demethylation was first reported 25 years ago but only in the past three years has data surfaced that can partially explain the elusive nature of this phenomenon. In addition to the global reorganization of the methylation and histone modification patterns, oocyte development prior to germinal vesicle breakdown involves the production of numerous small RNA, including miRNA. Despite their presence, miRNA functional activity is thought to be limited in the mature mouse oocyte. Additionally, molecular signatures in the 3' untranslated region of maternally expressed transcripts may impact mRNA stability during the transcriptionally quiescent period following germinal vesicle breakdown and prior to the maternal to zygote transition. In this review, we reference some of the recent works which attempt to shed light into the importance of the dynamic epigenetic landscape observed during oocyte maturation and preimplantation embryo development in mammals.
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19
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Sasaki A, de Vega WC, McGowan PO. Biological embedding in mental health: an epigenomic perspective. Biochem Cell Biol 2013; 91:14-21. [PMID: 23442137 DOI: 10.1139/bcb-2012-0070] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Human epidemiological studies and studies of animal models provide many examples by which early life experiences influence health in a long-term manner, a concept known as biological embedding. Such experiences can have profound impacts during periods of high plasticity in prenatal and early postnatal life. Epigenetic mechanisms influence gene function in the absence of changes in gene sequence. In contrast to the relative stability of gene sequences, epigenetic mechanisms appear, at least to some extent, responsive to environmental signals. To date, a few examples appear to clearly link early social experiences to epigenetic changes in pathways relevant for mental health in adulthood. Our recent work using high-throughput epigenomic techniques points to large-scale changes in gene pathways in addition to candidate genes involved in the response to psychosocial stress and neuroplasticity. Elucidation of which pathways are epigenetically labile under what conditions will enable a more complete understanding of how the epigenome can mediate environmental interactions with the genome that are relevant for mental health. In this mini-review, we provide examples of nascent research into the influence of early life experience on mental health outcomes, discuss evidence of epigenetic mechanisms that may underlie these effects, and describe challenges for research in this area.
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Affiliation(s)
- Aya Sasaki
- Department of Biological Sciences, University of Toronto, Scarborough, Canada
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20
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Dynamic deposition of histone variant H3.3 accompanies developmental remodeling of the Arabidopsis transcriptome. PLoS Genet 2012; 8:e1002658. [PMID: 22570629 PMCID: PMC3342937 DOI: 10.1371/journal.pgen.1002658] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Accepted: 03/04/2012] [Indexed: 12/21/2022] Open
Abstract
In animals, replication-coupled histone H3.1 can be distinguished from replication-independent histone H3.3. H3.3 variants are enriched at active genes and their promoters. Furthermore, H3.3 is specifically incorporated upon gene activation. Histone H3 variants evolved independently in plants and animals, and it is unclear whether different replication-independent H3.3 variants developed similar properties in both phyla. We studied Arabidopsis H3 variants in order to find core properties of this class of histones. Here we present genome-wide maps of H3.3 and H3.1 enrichment and the dynamic changes of their profiles upon cell division arrest. We find H3.3 enrichment to positively correlate with gene expression and to be biased towards the transcription termination site. In contrast with H3.1, heterochromatic regions are mostly depleted of H3.3. We report that, in planta, dynamic changes in H3.3 profiles are associated with the extensive remodeling of the transcriptome that occurs during cell differentiation. We propose that H3.3 dynamics are linked to transcription and are involved in resetting covalent histone marks at a genomic scale during plant development. Our study suggests that H3 variants properties likely result from functionally convergent evolution. Histone proteins are assembled into nucleosomes to build the skeleton of chromosomes. Beyond their role as DNA scaffold, histones participate in the regulation of gene activity. Studies in animals have shown that the deposition of two different histone H3 variants, H3.1 and H3.3, requires distinct pathways and results in distinct profiles throughout the genome. H3 variants evolved independently in plants and animals. Hence, H3 variants' properties shared by plants and animals would reflect core functions that have been selected during evolution. Our study indicates that these core properties include the high enrichment of H3.3 at active genes and a relative low deposition of H3.3 over regions deprived of genes or with inactive genes. In contrast with H3.1, H3.3 incorporation is dynamic and accompanies global changes of gene activity at major developmental transitions. We anticipate that the dynamic link between H3.3 variants and transcription enables remodeling of histone modifications that contribute to developmental transitions.
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21
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Yun M, Ruan C, Huh JW, Li B. Reconstitution of modified chromatin templates for in vitro functional assays. Methods Mol Biol 2012; 833:237-53. [PMID: 22183598 PMCID: PMC3749000 DOI: 10.1007/978-1-61779-477-3_15] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
To study the functions of histone modifications in the context of chromatin, it is necessary to be able to prepare nucleosomal templates that carry specific posttranslational modifications in a defined biochemical system. Here, we describe two sets of protocols for reconstituting designer nucleosomes that contain specifically modified histones. The resulting nucleosomes are suitable for electromobility shift assays, chromatin remodeling assays, and other functional and structural studies.
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Affiliation(s)
- Miyong Yun
- Department of Molecular Biology, UT Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9148
| | - Chun Ruan
- Department of Molecular Biology, UT Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9148
| | - Jae-Wan Huh
- Department of Molecular Biology, UT Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9148
| | - Bing Li
- Department of Molecular Biology, UT Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9148
,To whom correspondence should be addressed: W: (214) 648-1668, F: (214) 648-1490,
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22
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Abstract
Understanding the molecular mechanisms involved in the control of cell differentiation during embryonic development is currently one of the main objectives of developmental biology. This knowledge will provide a basis for the development of new strategies in the field of regenerative medicine, one of the most promising weapons to fight many human diseases. Cell differentiation during embryonic development is controlled primarily by epigenetic factors, that is, mechanisms involved in the regulation of chromatin structure and gene expression. Here we describe the best known epigenetic modifications, and pathways, mainly focused on DNA methylation and histone modifications, and try to depict the state of art in our knowledge about epigenetic regulation of embryonic stem cell maintenance and differentiation.
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23
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Environmental epigenomics: understanding the effects of parental care on the epigenome. Essays Biochem 2010; 48:275-87. [PMID: 20822499 DOI: 10.1042/bse0480275] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
An organism's behavioural and physiological and social milieu influence and are influenced by the epigenome, which is comprised predominantly of chromatin and the covalent modification of DNA by methylation. Epigenetic patterns are sculpted during development to shape the diversity of gene expression programmes in the organism. In contrast with the genetic sequence, which is determined by inheritance and is virtually identical in all tissues, the epigenetic pattern varies from cell type to cell type and is potentially dynamic throughout life. It is postulated that different environmental exposures could effect epigenetic patterns relevant for human behaviour. Because epigenetic programming defines the state of expression of genes, epigenetic differences could have the same consequences as genetic polymorphisms. Yet in contrast with genetic sequence differences, epigenetic alterations are potentially reversible. In the present chapter, we will discuss evidence that epigenetic processes early in life play a role in defining inter-individual trajectories of behaviour, with implications for mental health in adulthood.
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24
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Zygotic Resetting of the HISTONE 3 Variant Repertoire Participates in Epigenetic Reprogramming in Arabidopsis. Curr Biol 2010; 20:2137-43. [DOI: 10.1016/j.cub.2010.11.012] [Citation(s) in RCA: 186] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 10/30/2010] [Accepted: 11/02/2010] [Indexed: 01/19/2023]
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25
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Abstract
Several lines of evidence suggest the involvement of disturbance in epigenetic processes in autoimmune disease. Most noteworthy is the global DNA hypomethylation seen in lupus. Epigenetic states in difference from genetic lesions are potentially reversible and hence candidates for pharmacological intervention. Potential targets for drug development are histone modification and DNA methylating and demethylating enzymes. The most advanced set of drugs in clinical development are histone deacetylase (HDAC) inhibitors. However, the prevalence of DNA hypomethylation in lupus suggests that we should shift our attention from HDAC inhibitors to DNA demethylation inhibitors. MBD2 was recently proposed to be involved in demethylation in T cells in lupus and is, therefore, a candidate target. Although this field is at its infancy, it carries great promise.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, 3655 Sir William Osler Promenade, Montreal, QC, H3G 1Y6, Canada.
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26
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Drané P, Ouararhni K, Depaux A, Shuaib M, Hamiche A. The death-associated protein DAXX is a novel histone chaperone involved in the replication-independent deposition of H3.3. Genes Dev 2010; 24:1253-65. [PMID: 20504901 DOI: 10.1101/gad.566910] [Citation(s) in RCA: 504] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The histone variant H3.3 marks active chromatin by replacing the conventional histone H3.1. In this study, we investigate the detailed mechanism of H3.3 replication-independent deposition. We found that the death domain-associated protein DAXX and the chromatin remodeling factor ATRX (alpha-thalassemia/mental retardation syndrome protein) are specifically associated with the H3.3 deposition machinery. Bacterially expressed DAXX has a marked binding preference for H3.3 and assists the deposition of (H3.3-H4)(2) tetramers on naked DNA, thus showing that DAXX is a H3.3 histone chaperone. In DAXX-depleted cells, a fraction of H3.3 was found associated with the replication-dependent machinery of deposition, suggesting that cells adapt to the depletion. The reintroduced DAXX in these cells colocalizes with H3.3 into the promyelocytic leukemia protein (PML) bodies. Moreover, DAXX associates with pericentric DNA repeats, and modulates the transcription from these repeats through assembly of H3.3 nucleosomes. These findings establish a new link between the PML bodies and the regulation of pericentric DNA repeat chromatin structure. Taken together, our data demonstrate that DAXX functions as a bona fide histone chaperone involved in the replication-independent deposition of H3.3.
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Affiliation(s)
- Pascal Drané
- IGMBC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch F-67400, France
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27
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McGowan PO, Szyf M. The epigenetics of social adversity in early life: implications for mental health outcomes. Neurobiol Dis 2010; 39:66-72. [PMID: 20053376 DOI: 10.1016/j.nbd.2009.12.026] [Citation(s) in RCA: 216] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 12/20/2009] [Accepted: 12/26/2009] [Indexed: 11/16/2022] Open
Abstract
An organism's behavioral and physiological and social milieu influence and are influenced by the epigenome, which is composed predominantly of chromatin and the covalent modification of DNA by methylation. Epigenetic patterns are sculpted during development to shape the diversity of gene expression programs in the organism. In contrast to the genetic sequence, which is determined by inheritance and is virtually identical in all tissues, the epigenetic pattern varies from cell type to cell type and is potentially dynamic throughout life. It is postulated here that different environmental exposures, including early parental care, could impact epigenetic patterns, with important implications for mental health in humans. Because epigenetic programming defines the state of expression of genes, epigenetic differences could have the same consequences as genetic polymorphisms. Yet in contrast to genetic sequence differences, epigenetic alterations are potentially reversible. This review will discuss basic epigenetic mechanisms and how epigenetic processes early in life might play a role in defining inter-individual trajectories of human behavior. In this regard, we will examine evidence for the possibility that epigenetic mechanisms can contribute to later-onset neurological dysfunction and disease.
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Affiliation(s)
- Patrick O McGowan
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada
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28
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Ooi SL, Henikoff JG, Henikoff S. A native chromatin purification system for epigenomic profiling in Caenorhabditis elegans. Nucleic Acids Res 2009; 38:e26. [PMID: 19966274 PMCID: PMC2831312 DOI: 10.1093/nar/gkp1090] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
High-resolution mapping of chromatin features has emerged as an important strategy for understanding gene regulation and epigenetic inheritance. We describe an in vivo tagging system coupled to chromatin purification for genome-wide epigenetic profiling in Caenorhabditis elegans. In this system, we coexpressed the Escherichia coli biotin ligase enzyme (BirA), together with the C. elegans H3.3 gene fused to BioTag, a 23-amino-acid peptide serving as a biotinylation substrate for BirA, in vivo in worms. We found that the fusion BioTag::H3.3 was efficiently biotinylated in vivo. We developed methods to isolate chromatin under different salt extraction conditions, followed by affinity purification of biotinylated chromatin with streptavidin and genome-wide profiling with microarrays. We found that embryonic chromatin is differentially extracted with increasing salt concentrations. Interestingly, chromatin that remains insoluble after washing in 600 mM salt is enriched at 5′ and 3′ ends, suggesting the presence of large protein complexes that render chromatin insoluble at transcriptional initiation and termination sites. We also found that H3.3 landscapes from these salt fractions display consistent features that correlate with gene activity: the most highly expressed genes contain the most H3.3. This versatile two-component approach has the potential of facilitating genome-wide chromatin dynamics and regulatory site identification in C. elegans.
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Affiliation(s)
- Siew Loon Ooi
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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29
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Szyf M. The early life environment and the epigenome. Biochim Biophys Acta Gen Subj 2009; 1790:878-85. [PMID: 19364482 DOI: 10.1016/j.bbagen.2009.01.009] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 01/20/2009] [Accepted: 01/27/2009] [Indexed: 01/22/2023]
Abstract
Several lines of evidence point to the early origin of adult onset disease. A key question is: what are the mechanisms that mediate the effects of the early environment on our health? Another important question is: what is the impact of the environment during adulthood and how reversible are the effects of early life later in life? The genome is programmed by the epigenome, which is comprised of chromatin, a covalent modification of DNA by methylation and noncoding RNAs. The epigenome is sculpted during gestation, resulting in the diversity of gene expression programs in the distinct cell types of the organism. Recent data suggest that epigenetic programming of gene expression profiles is sensitive to the early-life environment and that both the chemical and social environment early in life could affect the manner by which the genome is programmed by the epigenome. We propose that epigenetic alterations early in life can have a life-long lasting impact on gene expression and thus on the phenotype, including susceptibility to disease. We will discuss data from animal models as well as recent data from human studies supporting the hypothesis that early life social-adversity leaves its marks on our epigenome and affects stress responsivity, health, and mental health later in life.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
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30
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Vogel MJ, Pagie L, Talhout W, Nieuwland M, Kerkhoven RM, van Steensel B. High-resolution mapping of heterochromatin redistribution in a Drosophila position-effect variegation model. Epigenetics Chromatin 2009; 2:1. [PMID: 19178722 PMCID: PMC2644302 DOI: 10.1186/1756-8935-2-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 01/29/2009] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Position-effect variegation (PEV) is the stochastic transcriptional silencing of a gene positioned adjacent to heterochromatin. white-mottled X-chromosomal inversions in Drosophila are classic PEV models that show variegation of the eye color gene white due to its relocation next to pericentric heterochromatin. It has been suggested that in these models the spreading of heterochromatin across the rearrangement breakpoint causes the silencing of white. However, the extent of this spreading and the precise pattern of heterochromatin redistribution have remained unclear. To obtain insight into the mechanism of PEV, we constructed high-resolution binding maps of Heterochromatin Protein 1 (HP1) on white-mottled chromosomes. RESULTS We find that HP1 invades euchromatin across the inversion breakpoints over approximately 175 kb and approximately 30 kb, causing de novo association of HP1 with 20 genes. However, HP1 binding levels in these regions show substantial local variation, and white is the most strongly bound gene. Remarkably, white is also the only gene that is detectably repressed by heterochromatin. Furthermore, we find that HP1 binding to the invaded region is particularly sensitive to the dosage of the histone methyltransferase Su(var)3-9, indicating that the de novo formed heterochromatin is less stable than naturally occurring constitutive heterochromatin. CONCLUSION Our molecular maps demonstrate that heterochromatin can invade a normally euchromatic region, yet the strength of HP1 binding and effects on gene expression are highly dependent on local context. Our data suggest that the white gene has an unusual intrinsic affinity for heterochromatin, which may cause this gene to be more sensitive to PEV than most other genes.
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Affiliation(s)
- Maartje J Vogel
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
| | - Ludo Pagie
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
| | - Wendy Talhout
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
| | - Marja Nieuwland
- Central Microarray Facility, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
| | - Ron M Kerkhoven
- Central Microarray Facility, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
| | - Bas van Steensel
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
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31
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Stover PJ, Caudill MA. Genetic and epigenetic contributions to human nutrition and health: managing genome-diet interactions. ACTA ACUST UNITED AC 2008; 108:1480-7. [PMID: 18755320 DOI: 10.1016/j.jada.2008.06.430] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Accepted: 02/04/2008] [Indexed: 01/24/2023]
Abstract
The Institute of Medicine recently convened a workshop to review the state of the various domains of nutritional genomics research and policy and to provide guidance for further development and translation of this knowledge into nutrition practice and policy. Nutritional genomics holds the promise to revolutionize both clinical and public health nutrition practice and facilitate the establishment of (a) genome-informed nutrient and food-based dietary guidelines for disease prevention and healthful aging, (b) individualized medical nutrition therapy for disease management, and (c) better targeted public health nutrition interventions (including micronutrient fortification and supplementation) that maximize benefit and minimize adverse outcomes within genetically diverse human populations. As the field of nutritional genomics matures, which will include filling fundamental gaps in knowledge of nutrient-genome interactions in health and disease and demonstrating the potential benefits of customizing nutrition prescriptions based on genetics, registered dietitians will be faced with the opportunity of making genetically driven dietary recommendations aimed at improving human health.
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Affiliation(s)
- Patrick J Stover
- Cornell University, Division of Nutritional Sciences, Ithaca, NY 14853, USA.
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32
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Abstract
The long-term effects of behaviour and environmental exposures, particularly during childhood, on health outcomes are well documented. Particularly thought provoking is the notion that exposures to different social environments have a long-lasting impact on human physical health. However, the mechanisms mediating the effects of the environment are still unclear. In the last decade, the main focus of attention was the genome, and interindividual genetic polymorphisms were sought after as the principal basis for susceptibility to disease. However, it is becoming clear that recent dramatic increases in the incidence of certain human pathologies, such as asthma and type 2 diabetes, cannot be explained just on the basis of a genetic drift. It is therefore extremely important to unravel the molecular links between the "environmental" exposure, which is believed to be behind this emerging incidence in certain human pathologies, and the disease's molecular mechanisms. Although it is clear that most human pathologies involve long-term changes in gene function, these might be caused by mechanisms other than changes in the deoxyribonucleic acid (DNA) sequence. The genome is programmed by the epigenome, which is composed of chromatin and a covalent modification of DNA by methylation. It is postulated here that "epigenetic" mechanisms mediate the effects of behavioural and environmental exposures early in life, as well as lifelong environmental exposures and the susceptibility to disease later in life. In contrast to genetic sequence differences, epigenetic aberrations are potentially reversible, raising the hope for interventions that will be able to reverse deleterious epigenetic programming.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, Montréimeal, QC.
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33
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Garnier O, Laouiellé-Duprat S, Spillane C. Genomic imprinting in plants. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 626:89-100. [PMID: 18372793 DOI: 10.1007/978-0-387-77576-0_7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- Olivier Garnier
- Genetics and Biotechnology Lab, Department of Biochemistry, Biosciences Institute, University College Cork, Ireland
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34
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Abstract
The epigenome serves as an interface between the dynamic environment and the inherited static genome. The epigenome is comprised of chromatin and a covalent modification of DNA by methylation. The epigenome is sculpted during development to shape the diversity of gene expression programs in the different cell types of the organism by a highly organized process. Epigenetic aberrations have similar consequences to genetic polymorphisms resulting in variations in gene function. Recent data suggest that the epigenome is dynamic and is therefore responsive to environmental signals not only during the critical periods in development but also later in life as well. It is postulated here that not only chemicals but also exposure to social behavior, such as maternal care, could affect the epigenome. It is proposed that exposures to different environmental agents could lead to interindividual phenotypic diversity as well as differential susceptibility to disease and behavioral pathologies. Interindividual differences in the epigenetic state could also affect susceptibility to xenobiotics. Although our current understanding of how epigenetic mechanisms impact on the toxic action of xenobiotics is very limited, it is anticipated that in the future, epigenetics will be incorporated in the assessment of the safety of chemicals.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, 3655 Sir William Osler Promenade, Montréal, Québec H3G 1Y6, Canada.
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35
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Szyf M, Weaver I, Meaney M. Maternal care, the epigenome and phenotypic differences in behavior. Reprod Toxicol 2007; 24:9-19. [PMID: 17561370 DOI: 10.1016/j.reprotox.2007.05.001] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Revised: 04/26/2007] [Accepted: 05/02/2007] [Indexed: 01/24/2023]
Abstract
The genome is programmed by the epigenome, which is comprised of chromatin and a covalent modification of DNA by methylation. Epigenetic patterns are sculpted during development to shape the diversity of gene expression programs in the different cell types of the organism. The epigenome of the developing fetus is especially sensitive to maternal nutrition, and exposure to environmental toxins as well as psychological stress. It is postulated here that not only chemicals but also exposure of the young pup to social behavior, such as maternal care, could affect the epigenome. Since epigenetic programming defines the state of expression of genes, epigenetic differences could have the same consequences as genetic polymorphisms. We will propose here a mechanism linking maternal behavior and epigenetic programming and we will discuss the prospect that similar epigenetic variations generated during early life play a role in generating inter-individual differences in human behavior. We speculate that exposures to different environmental toxins, which affect the epigenetic machinery might alter long-established epigenetic programs in the brain.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, 3655 Sir William Osler Promenade, Montréal, Québec H3G 1Y6, Canada.
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36
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37
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Shivaswamy S, Iyer VR. Genome-wide analysis of chromatin status using tiling microarrays. Methods 2007; 41:304-11. [PMID: 17309841 PMCID: PMC1876658 DOI: 10.1016/j.ymeth.2006.11.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 09/23/2006] [Accepted: 11/14/2006] [Indexed: 10/23/2022] Open
Abstract
The eukaryotic genome is packaged into chromatin, and chromatin modification and remodeling play an important role in transcriptional regulation, DNA replication, recombination and repair. Recent findings have shown that various post-translational histone modifications cooperate to recruit different effector proteins that bring about mobilization of the nucleosomes and cause distinct downstream consequences. The combination of chromatin immunoprecipitation (ChIP) using antibodies directed against the core histones or specific histone modifications, with high-resolution tiling microarray analysis allows the examination of nucleosome occupancy and histone modification status genome-wide. Comparing genome-wide chromatin status with global gene expression patterns can reveal causal connections between specific patterns of histone modifications and the resulting gene expression. Here, we describe current methods based on recent advances in microarray technology to conduct such studies.
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Affiliation(s)
| | - Vishwanath R Iyer
- * Corresponding author. Phone: +1 512 232 7833 Fax: +1 512 232 3472 E-mail:
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38
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Razin SV, Iarovaia OV, Sjakste N, Sjakste T, Bagdoniene L, Rynditch AV, Eivazova ER, Lipinski M, Vassetzky YS. Chromatin domains and regulation of transcription. J Mol Biol 2007; 369:597-607. [PMID: 17466329 DOI: 10.1016/j.jmb.2007.04.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 03/27/2007] [Accepted: 04/02/2007] [Indexed: 12/20/2022]
Abstract
Compartmentalization and compaction of DNA in the nucleus is the characteristic feature of eukaryotic cells. A fully extended DNA molecule has to be compacted 100,000 times to fit within the nucleus. At the same time it is critical that various DNA regions remain accessible for interaction with regulatory factors and transcription/replication factories. This puzzle is solved at the level of DNA packaging in chromatin that occurs in several steps: rolling of DNA onto nucleosomes, compaction of nucleosome fiber with formation of the so-called 30 nm fiber, and folding of the latter into the giant (50-200 kbp) loops, fixed onto the protein skeleton, the nuclear matrix. The general assumption is that DNA folding in the cell nucleus cannot be uniform. It has been known for a long time that a transcriptionally active chromatin fraction is more sensitive to nucleases; this was interpreted as evidence for the less tight compaction of this fraction. In this review we summarize the latest results on structure of transcriptionally active chromatin and the mechanisms of transcriptional regulation in the context of chromatin dynamics. In particular the significance of histone modifications and the mechanisms controlling dynamics of chromatin domains are discussed as well as the significance of spatial organization of the genome for functioning of distant regulatory elements.
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Affiliation(s)
- Sergey V Razin
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
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39
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Abstract
At certain evolutionary junctures, two or more mutations participating in the build-up of a new complex function may be required to become available simultaneously in the same individuals. How could this happen in higher organisms whose populations are small compared to those of microbes, and in which chances of combined nearly simultaneous highly specific favorable mutations are correspondingly low? The question can in principle be answered for regulatory evolution, one of the basic processes of evolutionary change. A combined resetting of transcription rates in several genes could occur in the same individual. It is proposed that, in eukaryotes, changes in epigenetic trends and epigenetically transforming encounters between alternative chromatin structures could arise frequently enough so as to render probable particular conjunctions of changed transcription rates. Such conjunctions could involve mutational changes with low specificity requirements in gene-associated regions of non-protein-coding sequences. The effects of such mutations, notably when they determine the use of histone variants and covalent modifications of histones, can be among those that migrate along chromatin. Changes in chromatin structure are often cellularly inheritable over at least a limited number of generations of cells, and of individuals when the germ line is involved. SINEs and LINEs, which have been considered "junk DNA", are among the repeat sequences that would appear liable to have teleregulatory effects on the function of a nearby promoter, through changes in their numbers and distribution. There may also be present preexisting unstably inheritable epigenetic trends leading to cellular variegation, trends endemic in a cell population based on DNA sequences previously established in the neighborhood. Either way, epigenetically conditioned teleregulatory trends may display only limited penetrance. The imposition at a distance of new chromatin structures with regulatory impact can occur in cis as well as in trans, and is examined as intrachromosomally spreading teleregulation and interchromosomal "gene kissing". The chances for two or more particular epigenetically determined regulatory trends to occur together in a cell are increased thanks to the proposed low specificity requirements for most of the pertinent sequence changes in intergenic and intronic DNA or in the distribution of middle repetitive sequences that have teleregulatory impact. Inheritable epigenetic changes ("epimutations") with effects at a distance would then perdure over the number of generations required for "assimilation" of the several regulatory novelties through the occurrence and selection, gene by gene, of specific classical mutations. These mutations would have effects similar to the epigenetic effects, yet would provide stability and penetrance. The described epigenetic/genetic partnership may well at times have opened the way toward certain complex new functions. Thus, the presence of "junk DNA", through co-determining the (higher or lower) order and the variants of chromatin structure with regulatory effects at a distance, might make an important contribution to the evolution of complex organisms.
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Affiliation(s)
- Emile Zuckerkandl
- Department of Biological Sciences, Stanford University, Stanford, California 94305, USA
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40
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Zhang R, Chen W, Adams PD. Molecular dissection of formation of senescence-associated heterochromatin foci. Mol Cell Biol 2007; 27:2343-58. [PMID: 17242207 PMCID: PMC1820509 DOI: 10.1128/mcb.02019-06] [Citation(s) in RCA: 288] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Senescence is characterized by an irreversible cell proliferation arrest. Specialized domains of facultative heterochromatin, called senescence-associated heterochromatin foci (SAHF), are thought to contribute to the irreversible cell cycle exit in many senescent cells by repressing the expression of proliferation-promoting genes such as cyclin A. SAHF contain known heterochromatin-forming proteins, such as heterochromatin protein 1 (HP1) and the histone H2A variant macroH2A, and other specialized chromatin proteins, such as HMGA proteins. Previously, we showed that a complex of histone chaperones, histone repressor A (HIRA) and antisilencing function 1a (ASF1a), plays a key role in the formation of SAHF. Here we have further dissected the series of events that contribute to SAHF formation. We show that each chromosome condenses into a single SAHF focus. Chromosome condensation depends on the ability of ASF1a to physically interact with its deposition substrate, histone H3, in addition to its cochaperone, HIRA. In cells entering senescence, HP1gamma, but not the related proteins HP1alpha and HP1beta, becomes phosphorylated on serine 93. This phosphorylation is required for efficient incorporation of HP1gamma into SAHF. Remarkably, however, a dramatic reduction in the amount of chromatin-bound HP1 proteins does not detectably affect chromosome condensation into SAHF. Moreover, abundant HP1 proteins are not required for the accumulation in SAHF of histone H3 methylated on lysine 9, the recruitment of macroH2A proteins, nor other hallmarks of senescence, such as the expression of senescence-associated beta-galactosidase activity and senescence-associated cell cycle exit. Based on our results, we propose a stepwise model for the formation of SAHF.
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Affiliation(s)
- Rugang Zhang
- Department of Basic Science, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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41
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D'Alessio AC, Szyf M. Epigenetic tête-à-tête: the bilateral relationship between chromatin modifications and DNA methylation. Biochem Cell Biol 2007; 84:463-76. [PMID: 16936820 DOI: 10.1139/o06-090] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The epigenome, which comprises chromatin, associated proteins, and the pattern of covalent modification of DNA by methylation, sets up and maintains gene expression programs. It was originally believed that DNA methylation was the dominant reaction in determining the chromatin structure. However, emerging data suggest that chromatin can affect DNA methylation in both directions, triggering either de novo DNA methylation or demethylation. These events are particularly important for the understanding of cellular transformation, which requires a coordinated change in gene expression profiles. While genetic alterations can explain some of the changes, the important role of epigenetic reprogramming is becoming more and more evident. Cancer cells exhibit a paradoxical coexistence of global loss of DNA methylation with regional hypermethylation.
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Affiliation(s)
- Ana C D'Alessio
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir William Osler, Montreal, QC H3G 1Y6, Canada
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42
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Oster H, Damerow S, Hut RA, Eichele G. Transcriptional profiling in the adrenal gland reveals circadian regulation of hormone biosynthesis genes and nucleosome assembly genes. J Biol Rhythms 2007; 21:350-61. [PMID: 16998155 DOI: 10.1177/0748730406293053] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The master circadian pacemaker of the suprachiasmatic nuclei coordinates behavioral and physiological rhythms via synchronization of subordinate peripheral oscillators in the central nervous system and organs throughout the body. Among these organs, the adrenal glands hold a prime position because of their regulatory influence on numerous physiological functions via rhythmic secretion of catecholamines and corticoid hormones into the bloodstream. In this report, the authors perform whole genome microarray hybridization to characterize the circadian transcriptome of the murine adrenal. They show that ~5% of the mouse genome is under circadian control in this gland. Using gene ontology analysis, they identify classes of transcripts that may synchronize adrenal hormone production. The authors' expression profiling also revealed that multiple histone genes implicated in either DNA replication or transcriptional regulation are clock controlled, suggesting a novel way by which the circadian clock may regulate the chromatin state.
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Affiliation(s)
- Henrik Oster
- Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.
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