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Li W, Hu J, Song F, Yu J, Peng X, Zhang S, Wang L, Hu M, Liu JC, Wei Y, Xiao X, Li Y, Li D, Wang H, Zhou BR, Dai L, Mou Z, Zhou M, Zhang H, Zhou Z, Zhang H, Bai Y, Zhou JQ, Li W, Li G, Zhu P. Structural basis for linker histone H5-nucleosome binding and chromatin fiber compaction. Cell Res 2024:10.1038/s41422-024-01009-z. [PMID: 39103524 DOI: 10.1038/s41422-024-01009-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 07/20/2024] [Indexed: 08/07/2024] Open
Abstract
The hierarchical packaging of chromatin fibers plays a critical role in gene regulation. The 30-nm chromatin fibers, a central-level structure bridging nucleosomal arrays to higher-order organizations, function as the first level of transcriptional dormant chromatin. The dynamics of 30-nm chromatin fiber play a crucial role in biological processes related to DNA. Here, we report a 3.6-angstrom resolution cryogenic electron microscopy structure of H5-bound dodecanucleosome, i.e., the chromatin fiber reconstituted in the presence of linker histone H5, which shows a two-start left-handed double helical structure twisted by tetranucleosomal units. An atomic structural model of the H5-bound chromatin fiber, including an intact chromatosome, is built, which provides structural details of the full-length linker histone H5, including its N-terminal domain and an HMG-motif-like C-terminal domain. The chromatosome structure shows that H5 binds the nucleosome off-dyad through a three-contact mode in the chromatin fiber. More importantly, the H5-chromatin structure provides a fine molecular basis for the intra-tetranucleosomal and inter-tetranucleosomal interactions. In addition, we systematically validated the physiological functions and structural characteristics of the tetranucleosomal unit through a series of genetic and genomic studies in Saccharomyces cerevisiae and in vitro biophysical experiments. Furthermore, our structure reveals that multiple structural asymmetries of histone tails confer a polarity to the chromatin fiber. These findings provide structural and mechanistic insights into how a nucleosomal array folds into a higher-order chromatin fiber with a polarity in vitro and in vivo.
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Affiliation(s)
- Wenyan Li
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jie Hu
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Feng Song
- New Cornerstone Science Laboratory, Frontier Science Center for Immunology and Metabolism, Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan, Hubei, China
- Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou, Shangdong, China
| | - Juan Yu
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xin Peng
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Shuming Zhang
- Department of Public Health Laboratory Sciences, West China School of Public Health, Sichuan University, Chengdu, Sichuan, China
| | - Lin Wang
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Mingli Hu
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jia-Cheng Liu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Yu Wei
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xue Xiao
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Yan Li
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Dongyu Li
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Hui Wang
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Bing-Rui Zhou
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Linchang Dai
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zongjun Mou
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Min Zhou
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Haonan Zhang
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zheng Zhou
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Huidong Zhang
- Research Center for Environment and Female Reproductive Health, The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong, China
| | - Yawen Bai
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jin-Qiu Zhou
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Wei Li
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Guohong Li
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
- New Cornerstone Science Laboratory, Frontier Science Center for Immunology and Metabolism, Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan, Hubei, China.
| | - Ping Zhu
- Key Laboratory of Epigenetic Regulation and Intervention, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
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2
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Vivek Hari Sundar G, Madhu A, Archana A, Shivaprasad PV. Plant histone variants at the nexus of chromatin readouts, stress and development. Biochim Biophys Acta Gen Subj 2024; 1868:130539. [PMID: 38072208 DOI: 10.1016/j.bbagen.2023.130539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 11/21/2023] [Accepted: 12/05/2023] [Indexed: 12/17/2023]
Abstract
Histones are crucial proteins that are involved in packaging the DNA as condensed chromatin inside the eukaryotic cell nucleus. Rather than being static packaging units, these molecules undergo drastic variations spatially and temporally to facilitate accessibility of DNA to replication, transcription as well as wide range of gene regulatory machineries. In addition, incorporation of paralogous variants of canonical histones in the chromatin is ascribed to specific functions. Given the peculiar requirement of plants to rapidly modulate gene expression levels on account of their sessile nature, histones and their variants serve as additional layers of gene regulation. This review summarizes the mechanisms and implications of distribution, modifications and differential incorporation of histones and their variants across plant genomes, and outlines emerging themes.
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Affiliation(s)
- G Vivek Hari Sundar
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India
| | - Aravind Madhu
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India; SASTRA University, Thirumalaisamudram, Thanjavur 613 401, India
| | - A Archana
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India; SASTRA University, Thirumalaisamudram, Thanjavur 613 401, India
| | - P V Shivaprasad
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bangalore, India.
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3
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Verdikt R, Thienpont B. Epigenetic remodelling under hypoxia. Semin Cancer Biol 2024; 98:1-10. [PMID: 38029868 DOI: 10.1016/j.semcancer.2023.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/17/2023] [Accepted: 10/18/2023] [Indexed: 12/01/2023]
Abstract
Hypoxia is intrinsic to tumours and contributes to malignancy and metastasis while hindering the efficiency of existing treatments. Epigenetic mechanisms play a crucial role in the regulation of hypoxic cancer cell programs, both in the initial phases of sensing the decrease in oxygen levels and during adaptation to chronic lack of oxygen. During the latter, the epigenetic regulation of tumour biology intersects with hypoxia-sensitive transcription factors in a complex network of gene regulation that also involves metabolic reprogramming. Here, we review the current literature on the epigenetic control of gene programs in hypoxic cancer cells. We highlight common themes and features of such epigenetic remodelling and discuss their relevance for the development of therapeutic strategies.
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Affiliation(s)
- Roxane Verdikt
- Institute for Society and Genetics, University of California, Los Angeles, Los Angeles, CA, USA; Department of Human Genetics, KU Leuven, Leuven, Belgium; KU Leuven Institute for Single Cell Omics (LISCO), KU Leuven, Leuven, Belgium
| | - Bernard Thienpont
- Department of Human Genetics, KU Leuven, Leuven, Belgium; KU Leuven Institute for Single Cell Omics (LISCO), KU Leuven, Leuven, Belgium; KU Leuven Cancer Institute (LKI), KU Leuven, Leuven, Belgium.
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4
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Liu C, Yu J, Song A, Wang M, Hu J, Chen P, Zhao J, Li G. Histone H1 facilitates restoration of H3K27me3 during DNA replication by chromatin compaction. Nat Commun 2023; 14:4081. [PMID: 37429872 DOI: 10.1038/s41467-023-39846-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 06/30/2023] [Indexed: 07/12/2023] Open
Abstract
During cell renewal, epigenetic information needs to be precisely restored to maintain cell identity and genome integrity following DNA replication. The histone mark H3K27me3 is essential for the formation of facultative heterochromatin and the repression of developmental genes in embryonic stem cells. However, how the restoration of H3K27me3 is precisely achieved following DNA replication is still poorly understood. Here we employ ChOR-seq (Chromatin Occupancy after Replication) to monitor the dynamic re-establishment of H3K27me3 on nascent DNA during DNA replication. We find that the restoration rate of H3K27me3 is highly correlated with dense chromatin states. In addition, we reveal that the linker histone H1 facilitates the rapid post-replication restoration of H3K27me3 on repressed genes and the restoration rate of H3K27me3 on nascent DNA is greatly compromised after partial depletion of H1. Finally, our in vitro biochemical experiments demonstrate that H1 facilitates the propagation of H3K27me3 by PRC2 through compacting chromatin. Collectively, our results indicate that H1-mediated chromatin compaction facilitates the propagation and restoration of H3K27me3 after DNA replication.
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Affiliation(s)
- Cuifang Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
| | - Juan Yu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
| | - Aoqun Song
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Min Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
| | - Jiansen Hu
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Science, 100101, Beijing, China
| | - Ping Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
- Department of Immunology, School of Basic Medical Sciences, Beijing Key Laboratory for Tumor Invasion and Metastasis, Capital Medical University, 100069, Beijing, China
| | - Jicheng Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.
| | - Guohong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.
- University of Chinese Academy of Sciences, 100049, Beijing, China.
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University, 430072, Wuhan, China.
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5
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Di Stefano M, Cavalli G. Integrative studies of 3D genome organization and chromatin structure. Curr Opin Struct Biol 2022; 77:102493. [PMID: 36335845 DOI: 10.1016/j.sbi.2022.102493] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 10/03/2022] [Accepted: 10/04/2022] [Indexed: 11/06/2022]
Abstract
The structural organization of the genome is emerging as a crucial regulator of the cell state, affecting gene transcription, DNA replication, and repair. Over the last twenty years, increasing evidence prompted the development of new experimental techniques to study genome structure. In parallel with the complexity of the novel techniques, computational approaches have become an essential tool in any structural genomics laboratory to analyze and model the data. For biologists to be able to apply the most appropriate modeling approach, it is fundamental to understand the conceptual bases of distinct methods and the insights they can provide. Here, we will discuss recent advances that were possible thanks to 3D genome modeling, discuss their limitations and highlight future perspectives.
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Affiliation(s)
- Marco Di Stefano
- Institute of Human Genetics, CNRS and University of Montpellier, 34094 Cedex 5, 141 Rue de la Cardonille, 34090, Montpellier, France. https://twitter.com/@MarcDiEsse
| | - Giacomo Cavalli
- Institute of Human Genetics, CNRS and University of Montpellier, 34094 Cedex 5, 141 Rue de la Cardonille, 34090, Montpellier, France.
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6
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Mansisidor AR, Risca VI. Chromatin accessibility: methods, mechanisms, and biological insights. Nucleus 2022; 13:236-276. [PMID: 36404679 PMCID: PMC9683059 DOI: 10.1080/19491034.2022.2143106] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/23/2022] [Accepted: 10/30/2022] [Indexed: 11/22/2022] Open
Abstract
Access to DNA is a prerequisite to the execution of essential cellular processes that include transcription, replication, chromosomal segregation, and DNA repair. How the proteins that regulate these processes function in the context of chromatin and its dynamic architectures is an intensive field of study. Over the past decade, genome-wide assays and new imaging approaches have enabled a greater understanding of how access to the genome is regulated by nucleosomes and associated proteins. Additional mechanisms that may control DNA accessibility in vivo include chromatin compaction and phase separation - processes that are beginning to be understood. Here, we review the ongoing development of accessibility measurements, we summarize the different molecular and structural mechanisms that shape the accessibility landscape, and we detail the many important biological functions that are linked to chromatin accessibility.
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Affiliation(s)
- Andrés R. Mansisidor
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
| | - Viviana I. Risca
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
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7
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Peng A, Peng W, Wang R, Zhao H, Yu X, Sun Y. Regulation of 3D Organization and Its Role in Cancer Biology. Front Cell Dev Biol 2022; 10:879465. [PMID: 35757006 PMCID: PMC9213882 DOI: 10.3389/fcell.2022.879465] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 04/27/2022] [Indexed: 11/13/2022] Open
Abstract
Three-dimensional (3D) genomics is the frontier field in the post-genomics era, its foremost content is the relationship between chromatin spatial conformation and regulation of gene transcription. Cancer biology is a complex system resulting from genetic alterations in key tumor oncogenes and suppressor genes for cell proliferation, DNA replication, cell differentiation, and homeostatic functions. Although scientific research in recent decades has revealed how the genome sequence is mutated in many cancers, high-order chromosomal structures involved in the development and fate of cancer cells represent a crucial but rarely explored aspect of cancer genomics. Hence, dissection of the 3D genome conformation of cancer helps understand the unique epigenetic patterns and gene regulation processes that distinguish cancer biology from normal physiological states. In recent years, research in tumor 3D genomics has grown quickly. With the rapid progress of 3D genomics technology, we can now better determine the relationship between cancer pathogenesis and the chromatin structure of cancer cells. It is becoming increasingly explicit that changes in 3D chromatin structure play a vital role in controlling oncogene transcription. This review focuses on the relationships between tumor gene expression regulation, tumor 3D chromatin structure, and cancer phenotypic plasticity. Furthermore, based on the functional consequences of spatial disorganization in the cancer genome, we look forward to the clinical application prospects of 3D genomic biomarkers.
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Affiliation(s)
- Anghui Peng
- Zhuhai Interventional Medical Center, Zhuhai Precision Medical Center, Zhuhai People's Hospital, Zhuhai Hospital Affiliated with Jinan University, Jinan University, Zhuhai, China.,Guangdong Provincial Key Laboratory of Tumor Interventional Diagnosis and Treatment, Zhuhai Institute of Translational Medicine, Zhuhai People's Hospital Affiliated with Jinan University, Jinan University, Zhuhai, China
| | - Wang Peng
- Department of Oncology, Liuzhou People's Hospital, Liuzhou, China
| | - Ruiqi Wang
- Department of Pharmacy, Zhuhai People's Hospital, Zhuhai Hospital Affiliated with Jinan University, Jinan University, Zhuhai, China
| | - Hao Zhao
- The First College of Clinical Medical Science, China Three Gorges University, Yichang, China
| | - Xinyang Yu
- Zhuhai Interventional Medical Center, Zhuhai Precision Medical Center, Zhuhai People's Hospital, Zhuhai Hospital Affiliated with Jinan University, Jinan University, Zhuhai, China.,Guangdong Provincial Key Laboratory of Tumor Interventional Diagnosis and Treatment, Zhuhai Institute of Translational Medicine, Zhuhai People's Hospital Affiliated with Jinan University, Jinan University, Zhuhai, China
| | - Yihao Sun
- Zhuhai Interventional Medical Center, Zhuhai Precision Medical Center, Zhuhai People's Hospital, Zhuhai Hospital Affiliated with Jinan University, Jinan University, Zhuhai, China.,Guangdong Provincial Key Laboratory of Tumor Interventional Diagnosis and Treatment, Zhuhai Institute of Translational Medicine, Zhuhai People's Hospital Affiliated with Jinan University, Jinan University, Zhuhai, China
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8
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Epigenetic Mechanisms of HIV-1 Persistence. Vaccines (Basel) 2021; 9:vaccines9050514. [PMID: 34067608 PMCID: PMC8156729 DOI: 10.3390/vaccines9050514] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 05/01/2021] [Accepted: 05/11/2021] [Indexed: 12/14/2022] Open
Abstract
Eradicating HIV-1 in infected individuals will not be possible without addressing the persistence of the virus in its multiple reservoirs. In this context, the molecular characterization of HIV-1 persistence is key for the development of rationalized therapeutic interventions. HIV-1 gene expression relies on the redundant and cooperative recruitment of cellular epigenetic machineries to cis-regulatory proviral regions. Furthermore, the complex repertoire of HIV-1 repression mechanisms varies depending on the nature of the viral reservoir, although, so far, few studies have addressed the specific regulatory mechanisms of HIV-1 persistence in other reservoirs than the well-studied latently infected CD4+ T cells. Here, we present an exhaustive and updated picture of the heterochromatinization of the HIV-1 promoter in its different reservoirs. We highlight the complexity, heterogeneity and dynamics of the epigenetic mechanisms of HIV-1 persistence, while discussing the importance of further understanding HIV-1 gene regulation for the rational design of novel HIV-1 cure strategies.
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9
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Arora I, Tollefsbol TO. Computational methods and next-generation sequencing approaches to analyze epigenetics data: Profiling of methods and applications. Methods 2021; 187:92-103. [PMID: 32941995 PMCID: PMC7914156 DOI: 10.1016/j.ymeth.2020.09.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/08/2020] [Accepted: 09/10/2020] [Indexed: 12/20/2022] Open
Abstract
Epigenetics is mainly comprised of features that regulate genomic interactions thereby playing a crucial role in a vast array of biological processes. Epigenetic mechanisms such as DNA methylation and histone modifications influence gene expression by modulating the packaging of DNA in the nucleus. A plethora of studies have emphasized the importance of analyzing epigenetics data through genome-wide studies and high-throughput approaches, thereby providing key insights towards epigenetics-based diseases such as cancer. Recent advancements have been made towards translating epigenetics research into a high throughput approach such as genome-scale profiling. Amongst all, bioinformatics plays a pivotal role in achieving epigenetics-related computational studies. Despite significant advancements towards epigenomic profiling, it is challenging to understand how various epigenetic modifications such as chromatin modifications and DNA methylation regulate gene expression. Next-generation sequencing (NGS) provides accurate and parallel sequencing thereby allowing researchers to comprehend epigenomic profiling. In this review, we summarize different computational methods such as machine learning and other bioinformatics tools, publicly available databases and resources to identify key modifications associated with epigenetic machinery. Additionally, the review also focuses on understanding recent methodologies related to epigenome profiling using NGS methods ranging from library preparation, different sequencing platforms and analytical techniques to evaluate various epigenetic modifications such as DNA methylation and histone modifications. We also provide detailed information on bioinformatics tools and computational strategies responsible for analyzing large scale data in epigenetics.
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Affiliation(s)
- Itika Arora
- Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL 35294, USA.
| | - Trygve O Tollefsbol
- Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL 35294, USA; Comprehensive Center for Healthy Aging, University of Alabama Birmingham, 1530 3rd Avenue South, Birmingham, AL 35294, USA; Comprehensive Cancer Center, University of Alabama Birmingham, 1802 6th Avenue South, Birmingham, AL 35294, USA; Nutrition Obesity Research Center, University of Alabama Birmingham, 1675 University Boulevard, Birmingham, AL 35294, USA; Comprehensive Diabetes Center, University of Alabama Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
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10
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Mishmar D, Levin R, Naeem MM, Sondheimer N. Higher Order Organization of the mtDNA: Beyond Mitochondrial Transcription Factor A. Front Genet 2019; 10:1285. [PMID: 31998357 PMCID: PMC6961661 DOI: 10.3389/fgene.2019.01285] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 11/21/2019] [Indexed: 01/09/2023] Open
Abstract
The higher order organization of eukaryotic and prokaryotic genomes is pivotal in the regulation of gene expression. Specifically, chromatin accessibility in eukaryotes and nucleoid accessibility in bacteria are regulated by a cohort of proteins to alter gene expression in response to diverse physiological conditions. By contrast, prior studies have suggested that the mitochondrial genome (mtDNA) is coated solely by mitochondrial transcription factor A (TFAM), whose increased cellular concentration was proposed to be the major determinant of mtDNA packaging in the mitochondrial nucleoid. Nevertheless, recent analysis of DNase-seq and ATAC-seq experiments from multiple human and mouse samples suggest gradual increase in mtDNA occupancy during the course of embryonic development to generate a conserved footprinting pattern which correlate with sites that have low TFAM occupancy in vivo (ChIP-seq) and tend to adopt G-quadruplex structures. These findings, along with recent identification of mtDNA binding by known modulators of chromatin accessibility such as MOF, suggest that mtDNA higher order organization is generated by cross talk with the nuclear regulatory system, may have a role in mtDNA regulation, and is more complex than once thought.
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Affiliation(s)
- Dan Mishmar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Rotem Levin
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Mansur M Naeem
- Institute of Medical Sciences and the Department of Paediatrics, The University of Toronto, Toronto, ON, Canada
| | - Neal Sondheimer
- Institute of Medical Sciences and the Department of Paediatrics, The University of Toronto, Toronto, ON, Canada
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11
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Banerjee DR, Deckard CE, Zeng Y, Sczepanski JT. Acetylation of the histone H3 tail domain regulates base excision repair on higher-order chromatin structures. Sci Rep 2019; 9:15972. [PMID: 31685935 PMCID: PMC6828659 DOI: 10.1038/s41598-019-52340-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 10/15/2019] [Indexed: 02/07/2023] Open
Abstract
Despite recent evidence suggesting that histone lysine acetylation contributes to base excision repair (BER) in cells, their exact mechanistic role remains unclear. In order to examine the influence of histone acetylation on the initial steps of BER, we assembled nucleosome arrays consisting of homogeneously acetylated histone H3 (H3K18 and H3K27) and measured the repair of a site-specifically positioned 2′-deoxyuridine (dU) residue by uracil DNA glycosylase (UDG) and apurinic/apyrimidinic endonuclease 1 (APE1). We find that H3K18ac and H3K27ac differentially influence the combined activities of UDG/APE1 on compact chromatin, suggesting that acetylated lysine residues on the H3 tail domain play distinct roles in regulating the initial steps of BER. In addition, we show that the effects of H3 tail domain acetylation on UDG/APE1 activity are at the nucleosome level and do not influence higher-order chromatin folding. Overall, these results establish a novel regulatory role for histone H3 acetylation during the initiation of BER on chromatin.
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Affiliation(s)
- Deb Ranjan Banerjee
- Department of Chemistry, National Institute of Technology, Durgapur, West Bengal, India
| | - Charles E Deckard
- Department of Chemistry, Texas A&M University, College Station, Texas, 77843, United States
| | - Yu Zeng
- Department of Microbial Pathogenesis and Immunology, Texas A&M University, College Station, Texas, 77843, United States
| | - Jonathan T Sczepanski
- Department of Chemistry, Texas A&M University, College Station, Texas, 77843, United States.
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12
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Rougeot J, Chrispijn ND, Aben M, Elurbe DM, Andralojc KM, Murphy PJ, Jansen PWTC, Vermeulen M, Cairns BR, Kamminga LM. Maintenance of spatial gene expression by Polycomb-mediated repression after formation of a vertebrate body plan. Development 2019; 146:dev.178590. [PMID: 31488564 PMCID: PMC6803366 DOI: 10.1242/dev.178590] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 08/26/2019] [Indexed: 12/22/2022]
Abstract
Polycomb group (PcG) proteins are transcriptional repressors that are important regulators of cell fate during embryonic development. Among them, Ezh2 is responsible for catalyzing the epigenetic repressive mark H3K27me3 and is essential for animal development. The ability of zebrafish embryos lacking both maternal and zygotic ezh2 to form a normal body plan provides a unique model for comprehensively studying Ezh2 function during early development in vertebrates. By using a multi-omics approach, we found that Ezh2 is required for the deposition of H3K27me3 and is essential for proper recruitment of Polycomb group protein Rnf2. However, despite the complete absence of PcG-associated epigenetic mark and proteins, only minor changes in H3K4me3 deposition and gene and protein expression occur. These changes were mainly due to local dysregulation of transcription factors outside their normal expression boundaries. Altogether, our results in zebrafish show that Polycomb-mediated gene repression is important immediately after the body plan is formed to maintain spatially restricted expression profiles of transcription factors, and we highlight the differences that exist in the timing of PcG protein action between vertebrate species. Summary: Our unique zebrafish model of a maternal and zygotic mutant for the Polycomb group gene ezh2 reveals major conserved and divergent mechanisms in epigenetic gene repression during vertebrate development.
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Affiliation(s)
- Julien Rougeot
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Nijmegen 6525 GA, The Netherlands .,Radboud University Medical Center, Department of Molecular Biology, Nijmegen 6525 GA, The Netherlands
| | - Naomi D Chrispijn
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Nijmegen 6525 GA, The Netherlands
| | - Marco Aben
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Nijmegen 6525 GA, The Netherlands.,Radboud University Medical Center, Department of Molecular Biology, Nijmegen 6525 GA, The Netherlands
| | - Dei M Elurbe
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Nijmegen 6525 GA, The Netherlands.,Radboud University Medical Center, Department of Molecular Biology, Nijmegen 6525 GA, The Netherlands
| | - Karolina M Andralojc
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Nijmegen 6525 GA, The Netherlands
| | - Patrick J Murphy
- Howard Hughes Medical Institute, Department of Oncological Sciences and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.,Wilmot Cancer Institute, Rochester Center for Biomedical Informatics, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Pascal W T C Jansen
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Oncode Institute, Nijmegen 6525 GA, The Netherlands
| | - Michiel Vermeulen
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Oncode Institute, Nijmegen 6525 GA, The Netherlands
| | - Bradley R Cairns
- Howard Hughes Medical Institute, Department of Oncological Sciences and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Leonie M Kamminga
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Nijmegen 6525 GA, The Netherlands .,Radboud University Medical Center, Department of Molecular Biology, Nijmegen 6525 GA, The Netherlands
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13
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Chemical and biophysical methods to explore dynamic mechanisms of chromatin silencing. Curr Opin Chem Biol 2019; 51:1-10. [PMID: 30825740 DOI: 10.1016/j.cbpa.2019.01.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/15/2019] [Accepted: 01/25/2019] [Indexed: 12/19/2022]
Abstract
Chromatin, the nucleoprotein complex organizing the genome, is central in regulating gene expression and genome organization. Chromatin conformational dynamics, controlled by histone post-translational modifications (PTM) and effector proteins, play a key role in this regulatory function. Recent developments in chemical biology, cell biology, and biophysics sparked important new studies, which probe direct causal connections between histone PTMs, chromatin effector proteins that write or read these modifications, and the involved functional chromatin states. In particular, the mechanisms of heterochromatin silencing have been explored in great detail in recent years. These studies revealed the highly dynamic nature of this chromatin state, its conformational heterogeneity, and different mechanisms of its formation. Here, we review how chemical biology and biophysics shaped our current understanding of the dynamic processes observed in heterochromatin and discuss the emerging technologies to detect chromatin organization directly in the cellular environment.
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14
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Xiong C, Wen Z, Yu J, Chen J, Liu CP, Zhang X, Chen P, Xu RM, Li G. UBN1/2 of HIRA complex is responsible for recognition and deposition of H3.3 at cis-regulatory elements of genes in mouse ES cells. BMC Biol 2018; 16:110. [PMID: 30285846 PMCID: PMC6171237 DOI: 10.1186/s12915-018-0573-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 09/06/2018] [Indexed: 01/08/2023] Open
Abstract
Background H3.3 is an ancient and conserved H3 variant and plays essential roles in transcriptional regulation. HIRA complex, which is composed of HIRA, UBN1 or UBN2, and Cabin1, is a H3.3 specific chaperone complex. However, it still remains largely uncharacterized how HIRA complex specifically recognizes and deposits H3.3 to the chromatin, such as promoters and enhancers. Results In this study, we demonstrate that the UBN1 or UBN2 subunit is mainly responsible for specific recognition and direct binding of H3.3 by the HIRA complex. While the HIRA subunit can enhance the binding affinity of UBN1 toward H3.3, Cabin1 subunit cannot. We also demonstrate that both Ala87 and Gly90 residues of H3.3 are required and sufficient for the specific recognition and binding by UBN1. ChIP-seq studies reveal that two independent HIRA complexes (UBN1-HIRA and UBN2-HIRA) can cooperatively deposit H3.3 to cis-regulatory regions, including active promoters and active enhancers in mouse embryonic stem (mES) cells. Importantly, disruption of histone chaperone activities of UBN1 and UBN2 by FID/AAA mutation results in the defect of H3.3 deposition at promoters of developmental genes involved in neural differentiation, and subsequently causes the failure of activation of these genes during neural differentiation of mES cells. Conclusion Together, our results provide novel insights into the mechanism by which the HIRA complex specifically recognizes and deposits H3.3 at promoters and enhancers of developmental genes, which plays a critical role in neural differentiation of mES cells. Electronic supplementary material The online version of this article (10.1186/s12915-018-0573-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Chaoyang Xiong
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Zengqi Wen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Juan Yu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jun Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chao-Pei Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Xiaodong Zhang
- College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Ping Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Rui-Ming Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Guohong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
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15
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Azad GK, Swagatika S, Kumawat M, Kumawat R, Tomar RS. Modifying Chromatin by Histone Tail Clipping. J Mol Biol 2018; 430:3051-3067. [DOI: 10.1016/j.jmb.2018.07.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/10/2018] [Accepted: 07/10/2018] [Indexed: 12/15/2022]
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16
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Smith PJ, Darzynkiewicz Z, Errington RJ. Nuclear cytometry and chromatin organization. Cytometry A 2018; 93:771-784. [PMID: 30144297 DOI: 10.1002/cyto.a.23521] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 05/25/2018] [Accepted: 06/13/2018] [Indexed: 12/18/2022]
Abstract
The nuclear-targeting chemical probe, for the detection and quantification of DNA within cells, has been a mainstay of cytometry-from the colorimetric Feulgen stain to smart fluorescent agents with tuned functionality. The level of nuclear structure and function at which the probe aims to readout, or indeed at which a DNA-targeted drug acts, is shadowed by a wide range of detection modalities and analytical methods. These methods are invariably limited in terms of the resolution attainable versus the volume occupied by targeted chromatin structures. The scalar challenge arises from the need to understand the extent and different levels of compaction of genomic DNA and how such structures can be re-modeled, reported, or even perturbed by both probes and drugs. Nuclear cytometry can report on the complex levels of chromatin order, disorder, disassembly, and even active disruption by probes and drugs. Nuclear probes can report defining features of clinical and therapeutic interest as in NETosis and other cell death processes. New cytometric approaches continue to bridge the scalar challenges of analyzing chromatin organization. Advances in super-resolution microscopy address the resolution and depth of analysis issues in cellular systems. Typical of recent insights into chromatin organization enabled by exploiting a DNA interacting probe is ChromEM tomography (ChromEMT). ChromEMT uses the unique properties of the anthraquinone-based cytometric dye DRAQ5™ to reveal that local and global 3D chromatin structures effect differences in compaction. The focus of this review is nuclear and chromatin cytometry, with linked reference to DNA targeting probes and drugs as exemplified by the anthracenediones.
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Affiliation(s)
- Paul J Smith
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, UK
| | - Zbigniew Darzynkiewicz
- Department of Pathology, Brander Cancer Research Institute, New York Medical College, Valhalla, New York, 10595
| | - Rachel J Errington
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, UK
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17
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Mandemaker IK, Geijer ME, Kik I, Bezstarosti K, Rijkers E, Raams A, Janssens RC, Lans H, Hoeijmakers JH, Demmers JA, Vermeulen W, Marteijn JA. DNA damage-induced replication stress results in PA200-proteasome-mediated degradation of acetylated histones. EMBO Rep 2018; 19:embr.201745566. [PMID: 30104204 PMCID: PMC6172457 DOI: 10.15252/embr.201745566] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 07/06/2018] [Accepted: 07/16/2018] [Indexed: 12/21/2022] Open
Abstract
Histone acetylation influences protein interactions and chromatin accessibility and plays an important role in the regulation of transcription, replication, and DNA repair. Conversely, DNA damage affects these crucial cellular processes and induces changes in histone acetylation. However, a comprehensive overview of the effects of DNA damage on the histone acetylation landscape is currently lacking. To quantify changes in histone acetylation, we developed an unbiased quantitative mass spectrometry analysis on affinity‐purified acetylated histone peptides, generated by differential parallel proteolysis. We identify a large number of histone acetylation sites and observe an overall reduction of acetylated histone residues in response to DNA damage, indicative of a histone‐wide loss of acetyl modifications. This decrease is mainly caused by DNA damage‐induced replication stress coupled to specific proteasome‐dependent loss of acetylated histones. Strikingly, this degradation of acetylated histones is independent of ubiquitylation but requires the PA200‐proteasome activator, a complex that specifically targets acetylated histones for degradation. The uncovered replication stress‐induced degradation of acetylated histones represents an important chromatin‐modifying response to cope with replication stress.
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Affiliation(s)
- Imke K Mandemaker
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Marit E Geijer
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Iris Kik
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Karel Bezstarosti
- Proteomics Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Erikjan Rijkers
- Proteomics Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Anja Raams
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Roel C Janssens
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Hannes Lans
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Jan Hj Hoeijmakers
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands.,CECAD Forschungszentrum, Köln, Germany.,Princess Máxima Center for Pediatric Oncology, Bilthoven, The Netherlands
| | - Jeroen Aa Demmers
- Proteomics Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Wim Vermeulen
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Jurgen A Marteijn
- Department of Molecular Genetics, Oncode Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
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18
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Chromatin modulation and gene regulation in plants: insight about PRC1 function. Biochem Soc Trans 2018; 46:957-966. [DOI: 10.1042/bst20170576] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Revised: 05/24/2018] [Accepted: 05/25/2018] [Indexed: 02/07/2023]
Abstract
In plant and metazoan, Polycomb Group (PcG) proteins play key roles in regulating developmental processes by repression of gene expression. PcG proteins function as multi-protein complexes; among them the best characterized ones are Polycomb Repressive Complex 1 (PRC1) and PRC2. PRC2 catalyzes histone H3 lysine 27 trimethylation (H3K27me3), and PRC1 can bind H3K27me3 and catalyzes H2A monoubiquitination. While the PRC2 components and molecular functions are evolutionarily conserved, varied PRC1 complexes are found and they show high divergences between animals and plants. In addition to the core subunits, an exponentially increasing number of PRC1-associated factors have been identified in Arabidopsis thaliana. Recent studies have also unraveled cross-component interactions and intertwined roles of PRC1 and PRC2 in chromatin modulation. In addition, complexities of interactions and functions between PcG and Trithorax Group proteins have been observed. This short review summarizes up current knowledge to provide insight about repressive functional mechanism of PRC1 and its interplay with other factors.
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19
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Blumberg A, Danko CG, Kundaje A, Mishmar D. A common pattern of DNase I footprinting throughout the human mtDNA unveils clues for a chromatin-like organization. Genome Res 2018; 28:1158-1168. [PMID: 30002158 PMCID: PMC6071632 DOI: 10.1101/gr.230409.117] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 06/13/2018] [Indexed: 12/16/2022]
Abstract
Human mitochondrial DNA (mtDNA) is believed to lack chromatin and histones. Instead, it is coated solely by the transcription factor TFAM. We asked whether mtDNA packaging is more regulated than once thought. To address this, we analyzed DNase-seq experiments in 324 human cell types and found, for the first time, a pattern of 29 mtDNA Genomic footprinting (mt-DGF) sites shared by ∼90% of the samples. Their syntenic conservation in mouse DNase-seq experiments reflect selective constraints. Colocalization with known mtDNA regulatory elements, with G-quadruplex structures, in TFAM-poor sites (in HeLa cells) and with transcription pausing sites, suggest a functional regulatory role for such mt-DGFs. Altered mt-DGF pattern in interleukin 3-treated CD34+ cells, certain tissue differences, and significant prevalence change in fetal versus nonfetal samples, offer first clues to their physiological importance. Taken together, human mtDNA has a conserved protein-DNA organization, which is likely involved in mtDNA regulation.
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Affiliation(s)
- Amit Blumberg
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105 Israel
| | - Charles G Danko
- Baker Institute for Animal Health, Cornell University, Ithaca, New York 14853, USA
| | - Anshul Kundaje
- Department of Genetics, Stanford University, Stanford, California 94305-5120, USA
| | - Dan Mishmar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105 Israel
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20
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21
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Banerjee DR, Deckard CE, Elinski MB, Buzbee ML, Wang WW, Batteas JD, Sczepanski JT. Plug-and-Play Approach for Preparing Chromatin Containing Site-Specific DNA Modifications: The Influence of Chromatin Structure on Base Excision Repair. J Am Chem Soc 2018; 140:8260-8267. [PMID: 29883113 DOI: 10.1021/jacs.8b04063] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The genomic DNA of eukaryotic cells exists in the form of chromatin, the structure of which controls the biochemical accessibility of the underlying DNA to effector proteins. In order to gain an in depth molecular understanding of how chromatin structure regulates DNA repair, detailed in vitro biochemical and biophysical studies are required. However, because of challenges associated with reconstituting nucleosome arrays containing site-specifically positioned DNA modifications, such studies have been limited to the use of mono- and dinucleosomes as model in vitro substrates, which are incapable of folding into native chromatin structures. To address this issue, we developed a straightforward and general approach for assembling chemically defined oligonucleosome arrays (i.e., designer chromatin) containing site-specifically modified DNA. Our method takes advantage of nicking endonucleases to excise short fragments of unmodified DNA, which are subsequently replaced with synthetic oligonucleotides containing the desired modification. Using this approach, we prepared several oligonucleosome substrates containing precisely positioned 2'-deoxyuridine (dU) residues and examined the efficiency of base excision repair (BER) within several distinct chromatin architectures. We show that, depending on the translational position of the lesion, the combined catalytic activities of uracil DNA glycosylase (UDG) and apurinic/apyrimidinic endonuclease 1 (APE1) can be either inhibited by as much as 20-fold or accelerated by more than 5-fold within compact chromatin (i.e., the 30 nm fiber) relative to naked DNA. Moreover, we demonstrate that digestion of dU by UDG/APE1 proceeds much more rapidly in mononucleosomes than in compacted nucleosome arrays, thereby providing the first direct evidence that internucleosome interactions play an important role in regulating BER within higher-order chromatin structures. Overall, this work highlights the value of performing detailed biochemical studies on precisely modified chromatin substrates in vitro and provides a robust platform for investigating DNA modifications in chromatin biology.
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Affiliation(s)
- Deb Ranjan Banerjee
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Charles E Deckard
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Meagan B Elinski
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Meridith L Buzbee
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Wesley Wei Wang
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - James D Batteas
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Jonathan T Sczepanski
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
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22
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Korolev N, Lyubartsev AP, Nordenskiöld L. A systematic analysis of nucleosome core particle and nucleosome-nucleosome stacking structure. Sci Rep 2018; 8:1543. [PMID: 29367745 PMCID: PMC5784010 DOI: 10.1038/s41598-018-19875-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/04/2018] [Indexed: 12/13/2022] Open
Abstract
Chromatin condensation is driven by the energetically favourable interaction between nucleosome core particles (NCPs). The close NCP-NCP contact, stacking, is a primary structural element of all condensed states of chromatin in vitro and in vivo. However, the molecular structure of stacked nucleosomes as well as the nature of the interactions involved in its formation have not yet been systematically studied. Here we undertake an investigation of both the structural and physico-chemical features of NCP structure and the NCP-NCP stacking. We introduce an “NCP-centred” set of parameters (NCP-NCP distance, shift, rise, tilt, and others) that allows numerical characterisation of the mutual positions of the NCPs in the stacking and in any other structures formed by the NCP. NCP stacking in more than 140 published NCP crystal structures were analysed. In addition, coarse grained (CG) MD simulations modelling NCP condensation was carried out. The CG model takes into account details of the nucleosome structure and adequately describes the long range electrostatic forces as well as excluded volume effects acting in chromatin. The CG simulations showed good agreement with experimental data and revealed the importance of the H2A and H4 N-terminal tail bridging and screening as well as tail-tail correlations in the stacked nucleosomes.
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Affiliation(s)
- Nikolay Korolev
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
| | - Alexander P Lyubartsev
- Department of Materials and Environmental Chemistry, Stockholm University, 10691, Stockholm, Sweden
| | - Lars Nordenskiöld
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
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23
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Chen P, Li G. Structure and Epigenetic Regulation of Chromatin Fibers. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2017; 82:25-35. [PMID: 29167282 DOI: 10.1101/sqb.2017.82.033795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In eukaryotes, genomic DNA is hierarchically packaged by histones into chromatin on several levels to fit inside the nucleus. As a central-level structure between nucleosomal arrays and higher-order chromatin organizations, the 30-nm chromatin fiber and its dynamics play a crucial role in gene regulation. However, despite considerable efforts over the past three decades, the fundamental structure and its dynamic regulation of chromatin fibers still remain as a big challenge in molecular biology. Here, we mainly summarize the most recent progress in elucidating the structure of the 30-nm chromatin fiber in vitro and epigenetic regulation of chromatin fibers by chromatin factors, particularly histone variants. In addition, we also discuss recent studies in unraveling the three-dimensional organization of chromatin fibers in situ by genomic approaches and electron microscopy.
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Affiliation(s)
- Ping Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Guohong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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24
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Bryan LC, Weilandt DR, Bachmann AL, Kilic S, Lechner CC, Odermatt PD, Fantner GE, Georgeon S, Hantschel O, Hatzimanikatis V, Fierz B. Single-molecule kinetic analysis of HP1-chromatin binding reveals a dynamic network of histone modification and DNA interactions. Nucleic Acids Res 2017; 45:10504-10517. [PMID: 28985346 PMCID: PMC5737501 DOI: 10.1093/nar/gkx697] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 07/27/2017] [Indexed: 12/20/2022] Open
Abstract
Chromatin recruitment of effector proteins involved in gene regulation depends on multivalent interaction with histone post-translational modifications (PTMs) and structural features of the chromatin fiber. Due to the complex interactions involved, it is currently not understood how effectors dynamically sample the chromatin landscape. Here, we dissect the dynamic chromatin interactions of a family of multivalent effectors, heterochromatin protein 1 (HP1) proteins, using single-molecule fluorescence imaging and computational modeling. We show that the three human HP1 isoforms are recruited and retained on chromatin by a dynamic exchange between histone PTM and DNA bound states. These interactions depend on local chromatin structure, the HP1 isoforms as well as on PTMs on HP1 itself. Of the HP1 isoforms, HP1α exhibits the longest residence times and fastest binding rates due to DNA interactions in addition to PTM binding. HP1α phosphorylation further increases chromatin retention through strengthening of multivalency while reducing DNA binding. As DNA binding in combination with specific PTM recognition is found in many chromatin effectors, we propose a general dynamic capture mechanism for effector recruitment. Multiple weak protein and DNA interactions result in a multivalent interaction network that targets effectors to a specific chromatin modification state, where their activity is required.
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Affiliation(s)
- Louise C Bryan
- Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Daniel R Weilandt
- Laboratory of Computational Systems Biotechnology, ISIC, EPFL, 1015 Lausanne, Switzerland
| | - Andreas L Bachmann
- Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Sinan Kilic
- Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Carolin C Lechner
- Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Pascal D Odermatt
- Laboratory for Bio- and Nano instrumentation, Institute of Bioengineering, EPFL, 1015 Lausanne, Switzerland
| | - Georg E Fantner
- Laboratory for Bio- and Nano instrumentation, Institute of Bioengineering, EPFL, 1015 Lausanne, Switzerland
| | - Sandrine Georgeon
- ISREC foundation chair in translational oncology, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Oliver Hantschel
- ISREC foundation chair in translational oncology, School of Life Sciences, EPFL, 1015 Lausanne, Switzerland
| | - Vassily Hatzimanikatis
- Laboratory of Computational Systems Biotechnology, ISIC, EPFL, 1015 Lausanne, Switzerland
| | - Beat Fierz
- Laboratory of Biophysical Chemistry of Macromolecules, Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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25
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Tekel SJ, Haynes KA. Molecular structures guide the engineering of chromatin. Nucleic Acids Res 2017; 45:7555-7570. [PMID: 28609787 PMCID: PMC5570049 DOI: 10.1093/nar/gkx531] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/07/2017] [Indexed: 12/28/2022] Open
Abstract
Chromatin is a system of proteins, RNA, and DNA that interact with each other to organize and regulate genetic information within eukaryotic nuclei. Chromatin proteins carry out essential functions: packing DNA during cell division, partitioning DNA into sub-regions within the nucleus, and controlling levels of gene expression. There is a growing interest in manipulating chromatin dynamics for applications in medicine and agriculture. Progress in this area requires the identification of design rules for the chromatin system. Here, we focus on the relationship between the physical structure and function of chromatin proteins. We discuss key research that has elucidated the intrinsic properties of chromatin proteins and how this information informs design rules for synthetic systems. Recent work demonstrates that chromatin-derived peptide motifs are portable and in some cases can be customized to alter their function. Finally, we present a workflow for fusion protein design and discuss best practices for engineering chromatin to assist scientists in advancing the field of synthetic epigenetics.
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Affiliation(s)
- Stefan J Tekel
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287, USA
| | - Karmella A Haynes
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287, USA
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Abstract
Skeletal muscle regeneration is an efficient stem cell-based repair system that ensures healthy musculature. For this repair system to function continuously throughout life, muscle stem cells must contribute to the process of myofiber repair as well as repopulation of the stem cell niche. The decision made by the muscle stem cells to commit to the muscle repair or to remain a stem cell depends upon patterns of gene expression, a process regulated at the epigenetic level. Indeed, it is well accepted that dynamic changes in epigenetic landscapes to control DNA accessibility and expression is a critical component during myogenesis for the effective repair of damaged muscle. Changes in the epigenetic landscape are governed by various posttranslational histone tail modifications, nucleosome repositioning, and DNA methylation events which collectively allow the control of changes in transcription networks during transitions of satellite cells from a dormant quiescent state toward terminal differentiation. This chapter focuses upon the specific epigenetic changes that occur during muscle stem cell-mediated regeneration to ensure myofiber repair and continuity of the stem cell compartment. Furthermore, we explore open questions in the field that are expected to be important areas of exploration as we move toward a more thorough understanding of the epigenetic mechanism regulating muscle regeneration.
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Affiliation(s)
- Daniel C L Robinson
- Sprott Centre for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada; University of Ottawa, Ottawa, ON, Canada
| | - Francis J Dilworth
- Sprott Centre for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada; University of Ottawa, Ottawa, ON, Canada.
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Meng H, Li H, Zheng Y, Yang Z, Jia Y, Bo S. Evolutionary analysis of nucleosome positioning sequences based on New Symmetric Relative Entropy. Genomics 2017; 110:154-161. [PMID: 28917635 DOI: 10.1016/j.ygeno.2017.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 09/06/2017] [Accepted: 09/12/2017] [Indexed: 10/18/2022]
Abstract
New Symmetric Relative Entropy (NSRE) was applied innovatively to analyze the nucleosome sequences in S. cerevisiae, S. pombe and Drosophila. NSRE distributions could well reflect the characteristic differences of nucleosome sequences among three organisms, and the differences indicate a concerted evolution in the sequence usage of nucleosome. Further analysis about the nucleosomes around TSS shows that the constitutive property of +1/-1 nucleosomes in S. cerevisiae is different from that in S. pombe and Drosophila, which indicates that S. cerevisiae has a different transcription regulation mechanism based on nucleosome. However, in either case, the nucleosome dyad region is conserved and always has a higher NSRE. Base composition analysis shows that this conservative property in nucleosome dyad region is mainly determined by base A and T, and the dependence degrees on base A and T are consistent in three organisms.
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Affiliation(s)
- Hu Meng
- Laboratory of Theoretical Biophysics, School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
| | - Hong Li
- Laboratory of Theoretical Biophysics, School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China.
| | - Yan Zheng
- Laboratory of Theoretical Biophysics, School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
| | - Zhenhua Yang
- Laboratory of Theoretical Biophysics, School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
| | - Yun Jia
- Laboratory of Theoretical Biophysics, School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
| | - Suling Bo
- Laboratory of Theoretical Biophysics, School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
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28
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Szewczak L. Seeing DNA Where It Lives. Cell 2017; 170:1045-1047. [PMID: 28886374 DOI: 10.1016/j.cell.2017.08.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It's the stuff of life, and we're fascinated by DNA and how it's packaged into chromatin and compacted into chromosomes. Advances in looking at chromatin organization in cells are letting us see this polymer, its packing, and its function with fresh eyes.
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29
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Wang Y, van Merwyk L, Tönsing K, Walhorn V, Anselmetti D, Fernàndez-Busquets X. Biophysical characterization of the association of histones with single-stranded DNA. Biochim Biophys Acta Gen Subj 2017; 1861:2739-2749. [PMID: 28756274 DOI: 10.1016/j.bbagen.2017.07.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 07/19/2017] [Accepted: 07/24/2017] [Indexed: 10/19/2022]
Abstract
BACKGROUND Despite the profound current knowledge of the architecture and dynamics of nucleosomes, little is known about the structures generated by the interaction of histones with single-stranded DNA (ssDNA), which is widely present during replication and transcription. METHODS Non-denaturing gel electrophoresis, transmission electron microscopy, atomic force microscopy, magnetic tweezers. RESULTS Histones have a high affinity for ssDNA in 0.15M NaCl ionic strength, with an apparent binding constant similar to that calculated for their association with double-stranded DNA (dsDNA). The length of DNA (number of nucleotides in ssDNA or base pairs in dsDNA) associated with a fixed core histone mass is the same for both ssDNA and dsDNA. Although histone-ssDNA complexes show a high tendency to aggregate, nucleosome-like structures are formed at physiological salt concentrations. Core histones are able to protect ssDNA from digestion by micrococcal nuclease, and a shortening of ssDNA occurs upon its interaction with histones. The purified (+) strand of a cloned DNA fragment of nucleosomal origin has a higher affinity for histones than the purified complementary (-) strand. CONCLUSIONS At physiological ionic strength histones have high affinity for ssDNA, possibly associating with it into nucleosome-like structures. GENERAL SIGNIFICANCE In the cell nucleus histones may spontaneously interact with ssDNA to facilitate their participation in the replication and transcription of chromatin.
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Affiliation(s)
- Ying Wang
- Experimental Biophysics and Applied Nanoscience, Faculty of Physics, Bielefeld University, Bielefeld 33615, Germany
| | - Luis van Merwyk
- Experimental Biophysics and Applied Nanoscience, Faculty of Physics, Bielefeld University, Bielefeld 33615, Germany
| | - Katja Tönsing
- Experimental Biophysics and Applied Nanoscience, Faculty of Physics, Bielefeld University, Bielefeld 33615, Germany
| | - Volker Walhorn
- Experimental Biophysics and Applied Nanoscience, Faculty of Physics, Bielefeld University, Bielefeld 33615, Germany
| | - Dario Anselmetti
- Experimental Biophysics and Applied Nanoscience, Faculty of Physics, Bielefeld University, Bielefeld 33615, Germany
| | - Xavier Fernàndez-Busquets
- Nanomalaria Group, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain; Barcelona Institute for Global Health (ISGlobal), Barcelona Center for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Rosselló 149-153, Barcelona 08036, Spain; Nanoscience and Nanotechnology Institute (IN2UB), University of Barcelona, Martí i Franquès 1, Barcelona 08028, Spain.
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Krzemien KM, Beckers M, Quack S, Michaelis J. Atomic force microscopy of chromatin arrays reveal non-monotonic salt dependence of array compaction in solution. PLoS One 2017; 12:e0173459. [PMID: 28296908 PMCID: PMC5351988 DOI: 10.1371/journal.pone.0173459] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 02/22/2017] [Indexed: 12/03/2022] Open
Abstract
Compaction of DNA in chromatin is a hallmark of the eukaryotic cell and unravelling its structure is required for an understanding of DNA involving processes. Despite strong experimental efforts, many questions concerning the DNA packing are open. In particular, it is heavily debated whether an ordered structure referred to as the “30 nm fibre” exist in vivo. Scanning probe microscopy has become a cutting edge technology for the high-resolution imaging of DNA- protein complexes. Here, we perform high-resolution atomic force microscopy of non-cross-linked chromatin arrays in liquid, under different salt conditions. A statistical analysis of the data reveals that array compaction is salt dependent in a non-monotonic fashion. A simple physical model can qualitatively explain the observed findings due to the opposing effects of salt dependent stiffening of DNA, nucleosome stability and histone-histone interactions. While for different salt concentrations different compaction states are observed, our data do not provide support for the existence of regular chromatin fibres. Our studies add new insights into chromatin structure, and with that contribute to a further understanding of the DNA condensation.
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Affiliation(s)
| | | | - Salina Quack
- Institute of Biophysics, Ulm University, Ulm, Germany
| | - Jens Michaelis
- Institute of Biophysics, Ulm University, Ulm, Germany
- * E-mail:
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31
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Bajpai G, Jain I, Inamdar MM, Das D, Padinhateeri R. Binding of DNA-bending non-histone proteins destabilizes regular 30-nm chromatin structure. PLoS Comput Biol 2017; 13:e1005365. [PMID: 28135276 PMCID: PMC5305278 DOI: 10.1371/journal.pcbi.1005365] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 02/13/2017] [Accepted: 01/14/2017] [Indexed: 11/18/2022] Open
Abstract
Why most of the in vivo experiments do not find the 30-nm chromatin fiber, well studied in vitro, is a puzzle. Two basic physical inputs that are crucial for understanding the structure of the 30-nm fiber are the stiffness of the linker DNA and the relative orientations of the DNA entering/exiting nucleosomes. Based on these inputs we simulate chromatin structure and show that the presence of non-histone proteins, which bind and locally bend linker DNA, destroys any regular higher order structures (e.g., zig-zag). Accounting for the bending geometry of proteins like nhp6 and HMG-B, our theory predicts phase-diagram for the chromatin structure as a function of DNA-bending non-histone protein density and mean linker DNA length. For a wide range of linker lengths, we show that as we vary one parameter, that is, the fraction of bent linker region due to non-histone proteins, the steady-state structure will show a transition from zig-zag to an irregular structure-a structure that is reminiscent of what is observed in experiments recently. Our theory can explain the recent in vivo observation of irregular chromatin having co-existence of finite fraction of the next-neighbor (i + 2) and neighbor (i + 1) nucleosome interactions.
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Affiliation(s)
- Gaurav Bajpai
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Ishutesh Jain
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Mandar M. Inamdar
- Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Dibyendu Das
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
- * E-mail:
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32
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Computational inference of physical spatial organization of eukaryotic genomes. QUANTITATIVE BIOLOGY 2016. [DOI: 10.1007/s40484-016-0082-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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33
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Zhu P, Li G. Higher-order structure of the 30-nm chromatin fiber revealed by cryo-EM. IUBMB Life 2016; 68:873-878. [PMID: 27704715 DOI: 10.1002/iub.1568] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2016] [Accepted: 09/14/2016] [Indexed: 11/07/2022]
Abstract
Genomic DNA is hierarchically packaged into chromatin in eukaryotes. As a central-level chromatin structure between nucleosomal arrays and higher order organizations, 30 nm chromatin fiber, and its dynamics play a crucial role in regulating DNA accessibility for gene transcription. However, despite extensive efforts over three decades, the higher-order structure of the 30 nm chromatin fiber remains unresolved and controversial. We have recently reconstituted the 30 nm chromatin fibers from 12 nucleosomal arrays in vitro in the presence of linker histone H1, and determined their cryo-EM structures at resolution of 11 Å (Song et al., Science 344, 376-380). Here, we briefly reviewed the higher-order structure studies of chromatin fibers, mainly focusing on the insights from the cryo-EM structures we recently solved. © 2016 IUBMB Life, 68(11):873-878, 2016.
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Affiliation(s)
- Ping Zhu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
| | - Guohong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
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34
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Pires RH, Felix SB, Delcea M. The architecture of neutrophil extracellular traps investigated by atomic force microscopy. NANOSCALE 2016; 8:14193-14202. [PMID: 27387552 DOI: 10.1039/c6nr03416k] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Neutrophils are immune cells that engage in a suicidal pathway leading to the release of partially decondensed chromatin, or neutrophil extracellular traps (NETs). NETs behave as a double edged sword; they can bind to pathogens thereby ensnaring them and limiting their spread during infection; however, they may bind to host circulating materials and trigger thrombotic events, and are associated with autoimmune disorders. Despite the fundamental role of NETs as part of an immune system response, there is currently a very poor understanding of how their nanoscale properties are reflected in their macroscopic impact. In this work, using a combination of fluorescence and atomic force microscopy, we show that NETs appear as a branching filament network that results in a substantially organized porous structure with openings with 0.03 ± 0.04 μm(2) on average and thus in the size range of small pathogens. Topological profiles typically up to 3 ± 1 nm in height are compatible with a "beads on a string" model of nucleosome chromatin. Typical branch lengths of 153 ± 103 nm appearing as rigid rods and height profiles of naked DNA in NETs of 1.2 ± 0.5 nm are indicative of extensive DNA supercoiling throughout NETs. The presence of DNA duplexes could also be inferred from force spectroscopy and the occurrence of force plateaus that ranged from ∼65 pN to 300 pN. Proteolytic digestion of NETs resulted in widespread disassembly of the network structure and considerable loss of mechanical properties. Our results suggest that the underlying structure of NETs is considerably organized and that part of its protein content plays an important role in maintaining its mesh architecture. We anticipate that NETs may work as microscopic mechanical sieves with elastic properties that stem from their DNA-protein composition, which is able to segregate particles also as a result of their size. Such a behavior may explain their participation in capturing pathogens and their association with thrombosis.
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Affiliation(s)
- Ricardo H Pires
- ZIK HIKE - Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University of Greifswald, Germany.
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35
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Gao S, Zhang L, Rao VB. Exclusion of small terminase mediated DNA threading models for genome packaging in bacteriophage T4. Nucleic Acids Res 2016; 44:4425-39. [PMID: 26984529 PMCID: PMC4872099 DOI: 10.1093/nar/gkw184] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 03/04/2016] [Indexed: 11/17/2022] Open
Abstract
Tailed bacteriophages and herpes viruses use powerful molecular machines to package their genomes. The packaging machine consists of three components: portal, motor (large terminase; TerL) and regulator (small terminase; TerS). Portal, a dodecamer, and motor, a pentamer, form two concentric rings at the special five-fold vertex of the icosahedral capsid. Powered by ATPase, the motor ratchets DNA into the capsid through the portal channel. TerS is essential for packaging, particularly for genome recognition, but its mechanism is unknown and controversial. Structures of gear-shaped TerS rings inspired models that invoke DNA threading through the central channel. Here, we report that mutations of basic residues that line phage T4 TerS (gp16) channel do not disrupt DNA binding. Even deletion of the entire channel helix retained DNA binding and produced progeny phage in vivo. On the other hand, large oligomers of TerS (11-mers/12-mers), but not small oligomers (trimers to hexamers), bind DNA. These results suggest that TerS oligomerization creates a large outer surface, which, but not the interior of the channel, is critical for function, probably to wrap viral genome around the ring during packaging initiation. Hence, models involving TerS-mediated DNA threading may be excluded as an essential mechanism for viral genome packaging.
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Affiliation(s)
- Song Gao
- Department of Biology, The Catholic University of America, 620 Michigan Avenue Northeast, Washington, DC 20064, USA Jiangsu Key Laboratory of Marine Pharmaceutical Compound Screening, Huaihai Institute of Technology, Lianyungang 222005, China
| | - Liang Zhang
- Department of Biology, The Catholic University of America, 620 Michigan Avenue Northeast, Washington, DC 20064, USA
| | - Venigalla B Rao
- Department of Biology, The Catholic University of America, 620 Michigan Avenue Northeast, Washington, DC 20064, USA
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36
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Pandya-Jones A, Plath K. The "lnc" between 3D chromatin structure and X chromosome inactivation. Semin Cell Dev Biol 2016; 56:35-47. [PMID: 27062886 DOI: 10.1016/j.semcdb.2016.04.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Revised: 04/01/2016] [Accepted: 04/04/2016] [Indexed: 12/01/2022]
Abstract
The long non-coding RNA Xist directs a remarkable instance of developmentally regulated, epigenetic change known as X Chromosome Inactivation (XCI). By spreading in cis across the X chromosome from which it is expressed, Xist RNA facilitates the creation of a heritably silent, heterochromatic nuclear territory that displays a three-dimensional structure distinct from that of the active X chromosome. How Xist RNA attaches to and propagates across a chromosome and its influence over the three-dimensional (3D) structure of the inactive X are aspects of XCI that have remained largely unclear. Here, we discuss studies that have made significant contributions towards answering these open questions.
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Affiliation(s)
- Amy Pandya-Jones
- Department of Biological Chemistry, Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Kathrin Plath
- Department of Biological Chemistry, Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90095, USA.
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