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Castilho RM, Castilho LS, Palomares BH, Squarize CH. Determinants of Chromatin Organization in Aging and Cancer-Emerging Opportunities for Epigenetic Therapies and AI Technology. Genes (Basel) 2024; 15:710. [PMID: 38927646 PMCID: PMC11202709 DOI: 10.3390/genes15060710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2024] [Revised: 05/21/2024] [Accepted: 05/26/2024] [Indexed: 06/28/2024] Open
Abstract
This review article critically examines the pivotal role of chromatin organization in gene regulation, cellular differentiation, disease progression and aging. It explores the dynamic between the euchromatin and heterochromatin, coded by a complex array of histone modifications that orchestrate essential cellular processes. We discuss the pathological impacts of chromatin state misregulation, particularly in cancer and accelerated aging conditions such as progeroid syndromes, and highlight the innovative role of epigenetic therapies and artificial intelligence (AI) in comprehending and harnessing the histone code toward personalized medicine. In the context of aging, this review explores the use of AI and advanced machine learning (ML) algorithms to parse vast biological datasets, leading to the development of predictive models for epigenetic modifications and providing a framework for understanding complex regulatory mechanisms, such as those governing cell identity genes. It supports innovative platforms like CEFCIG for high-accuracy predictions and tools like GridGO for tailored ChIP-Seq analysis, which are vital for deciphering the epigenetic landscape. The review also casts a vision on the prospects of AI and ML in oncology, particularly in the personalization of cancer therapy, including early diagnostics and treatment optimization for diseases like head and neck and colorectal cancers by harnessing computational methods, AI advancements and integrated clinical data for a transformative impact on healthcare outcomes.
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Affiliation(s)
- Rogerio M. Castilho
- Laboratory of Epithelial Biology, Department of Periodontics and Oral Medicine, School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA; (L.S.C.); (C.H.S.)
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI 48109-1078, USA
| | - Leonard S. Castilho
- Laboratory of Epithelial Biology, Department of Periodontics and Oral Medicine, School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA; (L.S.C.); (C.H.S.)
| | - Bruna H. Palomares
- Oral Diagnosis Department, Piracicaba School of Dentistry, State University of Campinas, Piracicaba 13414-903, Sao Paulo, Brazil;
| | - Cristiane H. Squarize
- Laboratory of Epithelial Biology, Department of Periodontics and Oral Medicine, School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA; (L.S.C.); (C.H.S.)
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI 48109-1078, USA
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Yang J, Yen K, Mahony S. SEM: sized-based expectation maximization for characterizing nucleosome positions and subtypes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.17.562727. [PMID: 37904910 PMCID: PMC10614873 DOI: 10.1101/2023.10.17.562727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2023]
Abstract
Genome-wide nucleosome profiles are predominantly characterized using MNase-seq, which involves extensive MNase digestion and size selection to enrich for mono-nucleosome-sized fragments. Most available MNase-seq analysis packages assume that nucleosomes uniformly protect 147bp DNA fragments. However, some nucleosomes with atypical histone or chemical compositions protect shorter lengths of DNA. The rigid assumptions imposed by current nucleosome analysis packages ignore variation in nucleosome lengths, potentially blinding investigators to regulatory roles played by atypical nucleosomes. To enable the characterization of different nucleosome types from MNase-seq data, we introduce the Size-based Expectation Maximization (SEM) nucleosome calling package. SEM employs a hierarchical Gaussian mixture model to estimate the positions and subtype identity of nucleosomes from MNase-seq fragments. Nucleosome subtypes are automatically identified based on the distribution of protected DNA fragment lengths at nucleosome positions. Benchmark analysis indicates that SEM is on par with existing packages in terms of standard nucleosome-calling accuracy metrics, while uniquely providing the ability to characterize nucleosome subtype identities. Using SEM on a low-dose MNase H2B MNase-ChIP-seq dataset from mouse embryonic stem cells, we identified three nucleosome types: short-fragment nucleosomes, canonical nucleosomes, and di-nucleosomes. The short-fragment nucleosomes can be divided further into two subtypes based on their chromatin accessibility. Interestingly, the subset of short-fragment nucleosomes in accessible regions exhibit high MNase sensitivity and display distribution patterns around transcription start sites (TSSs) and CTCF peaks, similar to the previously reported "fragile nucleosomes". These SEM-defined accessible short-fragment nucleosomes are found not just in promoters, but also in enhancers and other regulatory regions. Additional investigations reveal their co-localization with the chromatin remodelers Chd6, Chd8, and Ep400. In summary, SEM provides an effective platform for distinguishing various nucleosome subtypes, paving the way for future exploration of non-standard nucleosomes.
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Affiliation(s)
- Jianyu Yang
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Kuangyu Yen
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Haihe Laboratory of Cell Ecosystem, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin 300020, China
- Department of Developmental Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Shaun Mahony
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
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Fisher MJ, Luse DS. Promoter-proximal nucleosomes attenuate RNA polymerase II transcription through TFIID. J Biol Chem 2023; 299:104928. [PMID: 37330174 PMCID: PMC10404688 DOI: 10.1016/j.jbc.2023.104928] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 05/08/2023] [Accepted: 06/08/2023] [Indexed: 06/19/2023] Open
Abstract
A nucleosome is typically positioned with its proximal edge (NPE) ∼50 bp downstream from the transcription start site of metazoan RNA polymerase II promoters. This +1 nucleosome has distinctive characteristics, including the presence of variant histone types and trimethylation of histone H3 at lysine 4. To address the role of these features in transcription complex assembly, we generated templates with four different promoters and nucleosomes located at a variety of downstream positions, which were transcribed in vitro using HeLa nuclear extracts. Two promoters lacked TATA elements, but all supported strong initiation from a single transcription start site. In contrast to results with minimal in vitro systems based on the TATA-binding protein (TBP), TATA promoter templates with a +51 NPE were transcriptionally inhibited in extracts; activity continuously increased as the nucleosome was moved downstream to +100. Inhibition was much more pronounced for the TATA-less promoters: +51 NPE templates were inactive, and substantial activity was only seen with the +100 NPE templates. Substituting the histone variants H2A.Z, H3.3, or both did not eliminate the inhibition. However, addition of excess TBP restored activity on nucleosomal templates with TATA promoters, even with an NPE at +20. Remarkably, nucleosomal templates with histone H3 trimethylated at lysine 4 are active with an NPE at +51 for both TATA and TATA-less promoters. Our results strongly suggest that the +1 nucleosome interferes with promoter recognition by TFIID. This inhibition can be overcome with TBP alone at TATA promoters or through positive interactions with histone modifications and TFIID.
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Affiliation(s)
- Michael J Fisher
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Donal S Luse
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.
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Villaman C, Pollastri G, Saez M, Martin AJ. Benefiting from the intrinsic role of epigenetics to predict patterns of CTCF binding. Comput Struct Biotechnol J 2023; 21:3024-3031. [PMID: 37266407 PMCID: PMC10229758 DOI: 10.1016/j.csbj.2023.05.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 05/11/2023] [Accepted: 05/11/2023] [Indexed: 06/03/2023] Open
Abstract
Motivation One of the most relevant mechanisms involved in the determination of chromatin structure is the formation of structural loops that are also related with the conservation of chromatin states. Many of these loops are stabilized by CCCTC-binding factor (CTCF) proteins at their base. Despite the relevance of chromatin structure and the key role of CTCF, the role of the epigenetic factors that are involved in the regulation of CTCF binding, and thus, in the formation of structural loops in the chromatin, is not thoroughly understood. Results Here we describe a CTCF binding predictor based on Random Forest that employs different epigenetic data and genomic features. Importantly, given the ability of Random Forests to determine the relevance of features for the prediction, our approach also shows how the different types of descriptors impact the binding of CTCF, confirming previous knowledge on the relevance of chromatin accessibility and DNA methylation, but demonstrating the effect of epigenetic modifications on the activity of CTCF. We compared our approach against other predictors and found improved performance in terms of areas under PR and ROC curves (PRAUC-ROCAUC), outperforming current state-of-the-art methods.
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Affiliation(s)
- Camilo Villaman
- Programa de Doctorado en Genómica Integrativa, Vicerrectoría de Investigación, Universidad Mayor, Santiago, Chile
- Laboratorio de Redes Biológicas, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Escuela de Ingeniería, Facultad de Ingeniería, Arquitectura y Diseño, Universidad San Sebastián, Santiago, Chile
| | | | - Mauricio Saez
- Centro de Oncología de Precisión, Facultad de Medicina y Ciencias de la Salud, Universidad Mayor, Santiago, Chile
- Laboratorio de Investigación en Salud de Precisión, Departamento de Procesos Diagnósticos y Evaluación, Facultad de Ciencias de la Salud, Universidad Católica de Temuco, Chile
| | - Alberto J.M. Martin
- Laboratorio de Redes Biológicas, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Escuela de Ingeniería, Facultad de Ingeniería, Arquitectura y Diseño, Universidad San Sebastián, Santiago, Chile
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Zahedi Y, Zeng S, Ekwall K. An essential role for the Ino80 chromatin remodeling complex in regulation of gene expression during cellular quiescence. Chromosome Res 2023; 31:14. [PMID: 37043046 PMCID: PMC10097750 DOI: 10.1007/s10577-023-09723-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 03/15/2023] [Accepted: 03/31/2023] [Indexed: 04/13/2023]
Abstract
Cellular quiescence is an important physiological state both in unicellular and multicellular eukaryotes. Quiescent cells are halted for proliferation and stop the cell cycle at the G0 stage. Using fission yeast as a model organism, we have previously found that several subunits of a conserved chromatin remodeling complex, Ino80C (INOsitol requiring nucleosome remodeling factor), are required for survival in quiescence. Here, we demonstrate that Ino80C has a key function in the regulation of gene expression in G0 cells. We show that null mutants for two Ino80C subunits, Iec1 and Ies2, a putative subunit Arp42, a null mutant for the histone variant H2A.Z, and a null mutant for the Inositol kinase Asp1 have very similar phenotypes in quiescence. These mutants show reduced transcription genome-wide and specifically fail to activate 149 quiescence genes, of which many are localized to the subtelomeric regions. Using spike in normalized ChIP-seq experiments, we show that there is a global reduction of H2A.Z levels in quiescent wild-type cells but not in iec1∆ cells and that a subtelomeric chromosome boundary element is strongly affected by Ino80C. Based on these observations, we propose a model in which Ino80C is evicting H2A.Z from chromatin in quiescent cells, thereby inactivating the subtelomeric boundary element, leading to a reorganization of the chromosome structure and activation of genes required to survive in quiescence.
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Affiliation(s)
- Yasaman Zahedi
- Department of Biosciences and Nutrition, Karolinska Institutet, Neo Building, 141 83, Huddinge, Sweden
| | - Shengyuan Zeng
- Department of Biosciences and Nutrition, Karolinska Institutet, Neo Building, 141 83, Huddinge, Sweden
| | - Karl Ekwall
- Department of Biosciences and Nutrition, Karolinska Institutet, Neo Building, 141 83, Huddinge, Sweden.
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6
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Bomber ML, Wang J, Liu Q, Barnett KR, Layden HM, Hodges E, Stengel KR, Hiebert SW. Human SMARCA5 is continuously required to maintain nucleosome spacing. Mol Cell 2023; 83:507-522.e6. [PMID: 36630954 PMCID: PMC9974918 DOI: 10.1016/j.molcel.2022.12.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Revised: 12/07/2022] [Accepted: 12/16/2022] [Indexed: 01/12/2023]
Abstract
Genetic models suggested that SMARCA5 was required for DNA-templated events including transcription, DNA replication, and DNA repair. We engineered a degron tag into the endogenous alleles of SMARCA5, a catalytic component of the imitation switch complexes in three different human cell lines to define the effects of rapid degradation of this key regulator. Degradation of SMARCA5 was associated with a rapid increase in global nucleosome repeat length, which may allow greater chromatin compaction. However, there were few changes in nascent transcription within the first 6 h of degradation. Nevertheless, we demonstrated a requirement for SMARCA5 to control nucleosome repeat length at G1/S and during the S phase. SMARCA5 co-localized with CTCF and H2A.Z, and we found a rapid loss of CTCF DNA binding and disruption of nucleosomal phasing around CTCF binding sites. This spatiotemporal analysis indicates that SMARCA5 is continuously required for maintaining nucleosomal spacing.
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Affiliation(s)
- Monica L Bomber
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Jing Wang
- Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, TN 37203, USA; Center for Quantitative Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Qi Liu
- Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, TN 37203, USA; Center for Quantitative Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Kelly R Barnett
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Hillary M Layden
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Emily Hodges
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Kristy R Stengel
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, USA.
| | - Scott W Hiebert
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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7
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Li S, Wei T, Panchenko AR. Histone variant H2A.Z modulates nucleosome dynamics to promote DNA accessibility. Nat Commun 2023; 14:769. [PMID: 36765119 PMCID: PMC9918499 DOI: 10.1038/s41467-023-36465-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 02/02/2023] [Indexed: 02/12/2023] Open
Abstract
Nucleosomes, containing histone variants H2A.Z, are important for gene transcription initiation and termination, chromosome segregation and DNA double-strand break repair, among other functions. However, the underlying mechanisms of how H2A.Z influences nucleosome stability, dynamics and DNA accessibility are not well understood, as experimental and computational evidence remains inconclusive. Our modeling efforts of human nucleosome stability and dynamics, along with comparisons with experimental data show that the incorporation of H2A.Z results in a substantial decrease of the energy barrier for DNA unwrapping. This leads to the spontaneous DNA unwrapping of about forty base pairs from both ends, nucleosome gapping and increased histone plasticity, which otherwise is not observed for canonical nucleosomes. We demonstrate that both N- and C-terminal tails of H2A.Z play major roles in these events, whereas the H3.3 variant exerts a negligible impact in modulating the DNA end unwrapping. In summary, our results indicate that H2A.Z deposition makes nucleosomes more mobile and DNA more accessible to transcriptional machinery and other chromatin components.
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Affiliation(s)
- Shuxiang Li
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada
| | - Tiejun Wei
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada
| | - Anna R Panchenko
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada. .,Department of Biology and Molecular Sciences, Queen's University, Kingston, ON, Canada. .,School of Computing, Queen's University, Kingston, ON, Canada. .,Ontario Institute of Cancer Research, Toronto, Canada.
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Sokolova V, Sarkar S, Tan D. Histone variants and chromatin structure, update of advances. Comput Struct Biotechnol J 2022; 21:299-311. [PMID: 36582440 PMCID: PMC9764139 DOI: 10.1016/j.csbj.2022.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 12/01/2022] [Accepted: 12/01/2022] [Indexed: 12/12/2022] Open
Abstract
Histone proteins are highly conserved among all eukaryotes. They have two important functions in the cell: to package the genomic DNA and to regulate gene accessibility. Fundamental to these functions is the ability of histone proteins to interact with DNA and to form the nucleoprotein complex called chromatin. One of the mechanisms the cells use to regulate chromatin and gene expression is through replacing canonical histones with their variants at specific loci to achieve functional consequence. Recent cryo-electron microscope (cryo-EM) studies of chromatin containing histone variants reveal new details that shed light on how variant-specific features influence the structures and functions of chromatin. In this article, we review the current state of knowledge on histone variants biochemistry and discuss the implication of these new structural information on histone variant biology and their functions in transcription.
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Interplay Between the Histone Variant H2A.Z and the Epigenome in Pancreatic Cancer. Arch Med Res 2022; 53:840-858. [PMID: 36470770 DOI: 10.1016/j.arcmed.2022.11.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 10/25/2022] [Accepted: 11/18/2022] [Indexed: 12/03/2022]
Abstract
BACKGROUND The oncogenic process is orchestrated by a complex network of chromatin remodeling elements that shape the cancer epigenome. Histone variant H2A.Z regulates DNA control elements such as promoters and enhancers in different types of cancer; however, the interplay between H2A.Z and the pancreatic cancer epigenome is unknown. OBJECTIVE This study analyzed the role of H2A.Z in different DNA regulatory elements. METHODS We performed Chromatin Immunoprecipitation Sequencing assays (ChiP-seq) with total H2A.Z and acetylated H2A.Z (acH2A.Z) antibodies and analyzed published data from ChIP-seq, RNA-seq, bromouridine labeling-UV and sequencing (BruUV-seq), Hi-C and ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) in the pancreatic cancer cell line PANC-1. RESULTS The results indicate that total H2A.Z facilitates the recruitment of RNA polymerase II and transcription factors at promoters and enhancers allowing the expression of pro-oncogenic genes. Interestingly, we demonstrated that H2A.Z is enriched in super-enhancers (SEs) contributing to the transcriptional activation of key genes implicated in tumor development. Importantly, we established that H2A.Z contributes to the three-dimensional (3D) genome organization of pancreatic cancer and that it is a component of the Topological Associated Domains (TADs) boundaries in PANC-1 and that total H2A.Z and acH2A.Z are associated with A and B compartments, respectively. CONCLUSIONS H2A.Z participates in the biology and development of pancreatic cancer by generating a pro-oncogenic transcriptome through its posttranslational modifications, interactions with different partners, and regulatory elements, contributing to the oncogenic 3D genome organization. These data allow us to understand the molecular mechanisms that promote an oncogenic transcriptome in pancreatic cancer mediated by H2A.Z.
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Wei Y, Sandhu E, Yang X, Yang J, Ren Y, Gao X. Bidirectional Functional Effects of Staphylococcus on Carcinogenesis. Microorganisms 2022; 10:microorganisms10122353. [PMID: 36557606 PMCID: PMC9783839 DOI: 10.3390/microorganisms10122353] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 11/20/2022] [Accepted: 11/23/2022] [Indexed: 11/29/2022] Open
Abstract
As a Gram-positive cocci existing in nature, Staphylococcus has a variety of species, such as Staphylococcus aureus and Staphylococcus epidermidis, etc. Growing evidence reveals that Staphylococcus is closely related to the occurrence and development of various cancers. On the one hand, cancer patients are more likely to suffer from bacterial infection and antibiotic-resistant strain infection compared to healthy controls. On the other hand, there exists an association between staphylococcal infection and carcinogenesis. Staphylococcus often plays a pathogenic role and evades the host immune system through surface adhesion molecules, α-hemolysin, PVL (Panton-Valentine leukocidin), SEs (staphylococcal enterotoxins), SpA (staphylococcal protein A), TSST-1 (Toxic shock syndrom toxin-1) and other factors. Staphylococcal nucleases (SNases) are extracellular nucleases that serve as genomic markers for Staphylococcus aureus. Interestingly, a human homologue of SNases, SND1 (staphylococcal nuclease and Tudor domain-containing 1), has been recognized as an oncoprotein. This review is the first to summarize the reported basic and clinical evidence on staphylococci and neoplasms. Investigations on the correlation between Staphylococcus and the occurrence, development, diagnosis and treatment of breast, skin, oral, colon and other cancers, are made from the perspectives of various virulence factors and SND1.
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Affiliation(s)
- Yuannan Wei
- Faculty of Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Esha Sandhu
- Faculty of Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Xi Yang
- Department of Immunology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Jie Yang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Department of Immunology, School of Basic Medical Science, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Key Laboratory of Cellular and Molecular Immunology in Tianjin, Excellent Talent Project, The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
| | - Yuanyuan Ren
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Department of Immunology, School of Basic Medical Science, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Key Laboratory of Cellular and Molecular Immunology in Tianjin, Excellent Talent Project, The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Correspondence: (Y.R.); (X.G.); Tel./Fax: +86-022-83336806 (X.G.)
| | - Xingjie Gao
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Department of Immunology, School of Basic Medical Science, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Key Laboratory of Cellular and Molecular Immunology in Tianjin, Excellent Talent Project, The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Medical University, Qixiangtai Road No. 22, Heping District, Tianjin 300070, China
- Correspondence: (Y.R.); (X.G.); Tel./Fax: +86-022-83336806 (X.G.)
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11
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Wang Q, Qi Y, Xiong F, Wang D, Wang B, Chen Y. The H2A.Z-KDM1A complex promotes tumorigenesis by localizing in the nucleus to promote SFRP1 promoter methylation in cholangiocarcinoma cells. BMC Cancer 2022; 22:1166. [PMID: 36368958 PMCID: PMC9652970 DOI: 10.1186/s12885-022-10279-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 11/03/2022] [Indexed: 11/13/2022] Open
Abstract
Background Intrahepatic cholangiocarcinoma (ICC), originating from the bile ducts, is the second most common primary liver malignancy, and its incidence has recently increased. H2A.Z, a highly conserved H2A variant, is emerging as a key regulatory molecule in cancer. However, its underlying mechanism of action in ICC cells remains unclear. Methods Here, we examined the expression of H2A.Z and SFRP1 in normal intrahepatic cholangiocytes, ICC cell lines, ICC tissue microarrays, and fresh specimens. The correlations between H2A.Z or SFRP1 expression and clinical features were analysed. The overall survival rate was analysed based on H2A.Z and SFRP1 expression. Immunoprecipitation was used to analyse the recruitment of KDM1A, and ChIP sequencing and BSP were used to analyse the enrichment of methylation-related molecules such as H3K4me1 and H3K4me2 in the SFRP1 promoter and reveal the underlying mechanisms. Knockdown and rescue experiments were used to determine the potential mechanism by which H2A.Z and SFRP1 promote tumorigenesis in vitro. Results We showed that upregulation of H2A.Z expression is linked to downregulation of SFRP1 expression in ICC tissues and poor overall survival in patients with ICC. H2A.Z interacted with KDM1A in the nucleus to bind to the -151 ~ -136 bp region upstream of the SFRP1 promoter to increase its demethylation in ICC cells. Functionally, H2A.Z silencing inhibited the proliferation and invasion of ICC cells, and these effects were mitigated by SFRP1 silencing in ICC cells. Conclusions Our findings reveal that H2A.Z inhibits SFRP1 expression through chromatin modification in the context of ICC by forming a complex with KDM1A in the nucleus. Supplementary Information The online version contains supplementary material available at 10.1186/s12885-022-10279-y.
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Simmons JR, An R, Amankwaa B, Zayac S, Kemp J, Labrador M. Phosphorylated histone variant γH2Av is associated with chromatin insulators in Drosophila. PLoS Genet 2022; 18:e1010396. [PMID: 36197938 PMCID: PMC9576066 DOI: 10.1371/journal.pgen.1010396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 10/17/2022] [Accepted: 08/24/2022] [Indexed: 11/27/2022] Open
Abstract
Chromatin insulators are responsible for orchestrating long-range interactions between enhancers and promoters throughout the genome and align with the boundaries of Topologically Associating Domains (TADs). Here, we demonstrate an association between gypsy insulator proteins and the phosphorylated histone variant H2Av (γH2Av), normally a marker of DNA double strand breaks. Gypsy insulator components colocalize with γH2Av throughout the genome, in polytene chromosomes and in diploid cells in which Chromatin IP data shows it is enriched at TAD boundaries. Mutation of insulator components su(Hw) and Cp190 results in a significant reduction in γH2Av levels in chromatin and phosphatase inhibition strengthens the association between insulator components and γH2Av and rescues γH2Av localization in insulator mutants. We also show that γH2Av, but not H2Av, is a component of insulator bodies, which are protein condensates that form during osmotic stress. Phosphatase activity is required for insulator body dissolution after stress recovery. Together, our results implicate the H2A variant with a novel mechanism of insulator function and boundary formation.
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Affiliation(s)
- James R. Simmons
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Ran An
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Bright Amankwaa
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Shannon Zayac
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Justin Kemp
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Mariano Labrador
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
- * E-mail:
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13
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Feng Y, Zhang Y, Lin Z, Ye X, Lin X, Lv L, Lin Y, Sun S, Qi Y, Lin X. Chromatin remodeler Dmp18 regulates apoptosis by controlling H2Av incorporation in Drosophila imaginal disc development. PLoS Genet 2022; 18:e1010395. [PMID: 36166470 PMCID: PMC9514664 DOI: 10.1371/journal.pgen.1010395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 08/23/2022] [Indexed: 11/18/2022] Open
Abstract
Programmed Cell Death (PCD) or apoptosis is a highly conserved biological process and plays essential roles both in the development and stress context. In Drosophila, expression of pro-apoptotic genes, including reaper (rpr), head involution defective (hid), grim, and sickle (skl), is sufficient to induce cell death. Here, we demonstrate that the chromatin remodeler Dmp18, the homolog of mammalian Znhit1, plays a crucial role in regulating apoptosis in eye and wing development. We showed that loss of Dmp18 disrupted eye and wing development, up-regulated transcription of pro-apoptotic genes, and induced apoptosis. Inhibition of apoptosis suppressed the eye defects caused by Dmp18 deletion. Furthermore, loss of Dmp18 disrupted H2Av incorporation into chromatin, promoted H3K4me3, but reduced H3K27me3 modifications on the TSS regions of pro-apoptotic genes. These results indicate that Dmp18 negatively regulates apoptosis by mediating H2Av incorporation and histone H3 modifications at pro-apoptotic gene loci for transcriptional regulation. Our study uncovers the role of Dmp18 in regulating apoptosis in Drosophila eye and wing development and provides insights into chromatin remodeling regulating apoptosis at the epigenetic levels.
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Affiliation(s)
- Ying Feng
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- * E-mail: (YF); (YQ); (XL)
| | - Yan Zhang
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhiqing Lin
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xiaolei Ye
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xue Lin
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Lixiu Lv
- The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yi Lin
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Shenfei Sun
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Greater Bay Area Institute of Precision Medicine (Guangzhou), Zhongshan Hospital, Fudan University, Shanghai, China
| | - Yun Qi
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
- * E-mail: (YF); (YQ); (XL)
| | - Xinhua Lin
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Greater Bay Area Institute of Precision Medicine (Guangzhou), Zhongshan Hospital, Fudan University, Shanghai, China
- * E-mail: (YF); (YQ); (XL)
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14
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Dehingia B, Milewska M, Janowski M, Pękowska A. CTCF shapes chromatin structure and gene expression in health and disease. EMBO Rep 2022; 23:e55146. [PMID: 35993175 PMCID: PMC9442299 DOI: 10.15252/embr.202255146] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 05/31/2022] [Accepted: 07/14/2022] [Indexed: 11/09/2022] Open
Abstract
CCCTC-binding factor (CTCF) is an eleven zinc finger (ZF), multivalent transcriptional regulator, that recognizes numerous motifs thanks to the deployment of distinct combinations of its ZFs. The great majority of the ~50,000 genomic locations bound by the CTCF protein in a given cell type is intergenic, and a fraction of these sites overlaps with transcriptional enhancers. Furthermore, a proportion of the regions bound by CTCF intersect genes and promoters. This suggests multiple ways in which CTCF may impact gene expression. At promoters, CTCF can directly affect transcription. At more distal sites, CTCF may orchestrate interactions between regulatory elements and help separate eu- and heterochromatic areas in the genome, exerting a chromatin barrier function. In this review, we outline how CTCF contributes to the regulation of the three-dimensional structure of chromatin and the formation of chromatin domains. We discuss how CTCF binding and architectural functions are regulated. We examine the literature implicating CTCF in controlling gene expression in development and disease both by acting as an insulator and a factor facilitating regulatory elements to efficiently interact with each other in the nuclear space.
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Affiliation(s)
- Bondita Dehingia
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental BiologyPolish Academy of SciencesWarsawPoland
| | - Małgorzata Milewska
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental BiologyPolish Academy of SciencesWarsawPoland
| | - Marcin Janowski
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental BiologyPolish Academy of SciencesWarsawPoland
| | - Aleksandra Pękowska
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental BiologyPolish Academy of SciencesWarsawPoland
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15
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Assignment of structural transitions during mechanical unwrapping of nucleosomes and their disassembly products. Proc Natl Acad Sci U S A 2022; 119:e2206513119. [PMID: 35939666 PMCID: PMC9388122 DOI: 10.1073/pnas.2206513119] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Nucleosomes, the fundamental structural unit of chromatin, consists of ∼147 DNA base pairs wrapped around a histone protein octamer. To characterize the strength of the nucleosomal barrier and its contribution as a mechanism of control of gene expression, it is essential to determine the forces required to unwrap the DNA from the core particle and the stepwise transitions involved. In this study, we performed combined optical tweezers and single-molecule fluorescence measurements to identify the specific DNA segments unwrapped during the force transitions observed in mechanical stretching of nucleosomes. Furthermore, we characterize the mechanical signatures of subnucleosomal hexasomes and tetrasomes. The characterization performed in this work is essential for the interpretation of ongoing studies of chromatin remodelers, polymerases, and histone chaperones. Nucleosome DNA unwrapping and its disassembly into hexasomes and tetrasomes is necessary for genomic access and plays an important role in transcription regulation. Previous single-molecule mechanical nucleosome unwrapping revealed a low- and a high-force transitions, and force-FRET pulling experiments showed that DNA unwrapping is asymmetric, occurring always first from one side before the other. However, the assignment of DNA segments involved in these transitions remains controversial. Here, using high-resolution optical tweezers with simultaneous single-molecule FRET detection, we show that the low-force transition corresponds to the undoing of the outer wrap of one side of the nucleosome (∼27 bp), a process that can occur either cooperatively or noncooperatively, whereas the high-force transition corresponds to the simultaneous unwrapping of ∼76 bp from both sides. This process may give rise stochastically to the disassembly of nucleosomes into hexasomes and tetrasomes whose unwrapping/rewrapping trajectories we establish. In contrast, nucleosome rewrapping does not exhibit asymmetry. To rationalize all previous nucleosome unwrapping experiments, it is necessary to invoke that mechanical unwrapping involves two nucleosome reorientations: one that contributes to the change in extension at the low-force transition and another that coincides but does not contribute to the high-force transition.
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16
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Boschiero C, Gao Y, Baldwin RL, Ma L, Li CJ, Liu GE. Differentially CTCF-Binding Sites in Cattle Rumen Tissue during Weaning. Int J Mol Sci 2022; 23:ijms23169070. [PMID: 36012336 PMCID: PMC9408924 DOI: 10.3390/ijms23169070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 08/09/2022] [Accepted: 08/11/2022] [Indexed: 11/17/2022] Open
Abstract
The weaning transition in calves is characterized by major structural changes such as an increase in the rumen capacity and surface area due to diet changes. Studies evaluating rumen development in calves are vital to identify genetic mechanisms affected by weaning. This study aimed to provide a genome-wide characterization of CTCF-binding sites and differentially CTCF-binding sites (DCBS) in rumen tissue during the weaning transition of four Holstein calves to uncover regulatory elements in rumen epithelial tissue using ChIP-seq. Our study generated 67,280 CTCF peaks for the before weaning (BW) and 39,891 for after weaning (AW). Then, 7401 DCBS were identified for the AW vs. BW comparison representing 0.15% of the cattle genome, comprising ~54% of induced DCBS and ~46% of repressed DCBS. Most of the induced and repressed DCBS were in distal intergenic regions, showing a potential role as insulators. Gene ontology enrichment revealed many shared GO terms for the induced and the repressed DCBS, mainly related to cellular migration, proliferation, growth, differentiation, cellular adhesion, digestive tract morphogenesis, and response to TGFβ. In addition, shared KEGG pathways were obtained for adherens junction and focal adhesion. Interestingly, other relevant KEGG pathways were observed for the induced DCBS like gastric acid secretion, salivary secretion, bacterial invasion of epithelial cells, apelin signaling, and mucin-type O-glycan biosynthesis. IPA analysis further revealed pathways with potential roles in rumen development during weaning, including TGFβ, Integrin-linked kinase, and Integrin signaling. When DCBS were further integrated with RNA-seq data, 36 putative target genes were identified for the repressed DCBS, including KRT84, COL9A2, MATN3, TSPAN1, and AJM1. This study successfully identified DCBS in cattle rumen tissue after weaning on a genome-wide scale and revealed several candidate target genes that may have a role in rumen development, such as TGFβ, integrins, keratins, and SMADs. The information generated in this preliminary study provides new insights into bovine genome regulation and chromatin landscape.
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Affiliation(s)
- Clarissa Boschiero
- Animal Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA
| | - Yahui Gao
- Animal Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA
- Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA
| | - Ransom L. Baldwin
- Animal Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA
| | - Li Ma
- Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA
| | - Cong-jun Li
- Animal Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA
- Correspondence: (C.-j.L.); (G.E.L.); Tel.: +1-301-504-7216 (C.-j.L.); +1-301-504-9843 (G.E.L.); Fax: +1-301-504-8414 (C.-j.L. & G.E.L.)
| | - George E. Liu
- Animal Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA
- Correspondence: (C.-j.L.); (G.E.L.); Tel.: +1-301-504-7216 (C.-j.L.); +1-301-504-9843 (G.E.L.); Fax: +1-301-504-8414 (C.-j.L. & G.E.L.)
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17
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Sun X, Zhang J, Cao C. CTCF and Its Partners: Shaper of 3D Genome during Development. Genes (Basel) 2022; 13:genes13081383. [PMID: 36011294 PMCID: PMC9407368 DOI: 10.3390/genes13081383] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 07/27/2022] [Accepted: 07/29/2022] [Indexed: 02/06/2023] Open
Abstract
The 3D genome organization and its dynamic modulate genome function, playing a pivotal role in cell differentiation and development. CTCF and cohesin, acting as the core architectural components involved in chromatin looping and genome folding, can also recruit other protein or RNA partners to fine-tune genome structure during development. Moreover, systematic screening for partners of CTCF has been performed through high-throughput approaches. In particular, several novel protein and RNA partners, such as BHLHE40, WIZ, MAZ, Aire, MyoD, YY1, ZNF143, and Jpx, have been identified, and these partners are mostly implicated in transcriptional regulation and chromatin remodeling, offering a unique opportunity for dissecting their roles in higher-order chromatin organization by collaborating with CTCF and cohesin. Here, we review the latest advancements with an emphasis on features of CTCF partners and also discuss the specific functions of CTCF-associated complexes in chromatin structure modulation, which may extend our understanding of the functions of higher-order chromatin architecture in developmental processes.
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Affiliation(s)
- Xiaoyue Sun
- Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China; (X.S.); (J.Z.)
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China
- Center for Reproductive Genetics and Reproductive Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China
| | - Jing Zhang
- Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China; (X.S.); (J.Z.)
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China
- Center for Reproductive Genetics and Reproductive Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China
| | - Chunwei Cao
- Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China; (X.S.); (J.Z.)
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China
- Center for Reproductive Genetics and Reproductive Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510275, China
- Guangzhou Laboratory, Guangzhou 510320, China
- Correspondence:
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18
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Dijkwel Y, Tremethick DJ. The Role of the Histone Variant H2A.Z in Metazoan Development. J Dev Biol 2022; 10:jdb10030028. [PMID: 35893123 PMCID: PMC9326617 DOI: 10.3390/jdb10030028] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/12/2022] [Accepted: 06/23/2022] [Indexed: 12/10/2022] Open
Abstract
During the emergence and radiation of complex multicellular eukaryotes from unicellular ancestors, transcriptional systems evolved by becoming more complex to provide the basis for this morphological diversity. The way eukaryotic genomes are packaged into a highly complex structure, known as chromatin, underpins this evolution of transcriptional regulation. Chromatin structure is controlled by a variety of different epigenetic mechanisms, including the major mechanism for altering the biochemical makeup of the nucleosome by replacing core histones with their variant forms. The histone H2A variant H2A.Z is particularly important in early metazoan development because, without it, embryos cease to develop and die. However, H2A.Z is also required for many differentiation steps beyond the stage that H2A.Z-knockout embryos die. H2A.Z can facilitate the activation and repression of genes that are important for pluripotency and differentiation, and acts through a variety of different molecular mechanisms that depend upon its modification status, its interaction with histone and nonhistone partners, and where it is deposited within the genome. In this review, we discuss the current knowledge about the different mechanisms by which H2A.Z regulates chromatin function at various developmental stages and the chromatin remodeling complexes that determine when and where H2A.Z is deposited.
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19
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Wang C, Xu Q, Zhang X, Day DS, Abraham BJ, Lun K, Chen L, Huang J, Ji X. BRD2 interconnects with BRD3 to facilitate Pol II transcription initiation and elongation to prime promoters for cell differentiation. Cell Mol Life Sci 2022; 79:338. [PMID: 35665862 PMCID: PMC11072765 DOI: 10.1007/s00018-022-04349-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 04/20/2022] [Accepted: 05/04/2022] [Indexed: 11/03/2022]
Abstract
The bromodomain and extraterminal motif (BET) proteins are critical drug targets for diseases. The precise functions and relationship of BRD2 with other BET proteins remain elusive mechanistically. Here, we used acute protein degradation and quantitative genomic and proteomic approaches to investigate the primary functions of BRD2 in transcription. We report that BRD2 is required for TAF3-mediated Pol II initiation at promoters with low levels of H3K4me3 and for R-loop suppression during Pol II elongation. Single and double depletion revealed that BRD2 and BRD3 function additively, independently, or perhaps antagonistically in Pol II transcription at different promoters. Furthermore, we found that BRD2 regulates the expression of different genes during embryonic body differentiation processes by promoter priming in embryonic stem cells. Therefore, our results suggest complex interconnections between BRD2 and BRD3 at promoters to fine-tune Pol II initiation and elongation for control of cell state.
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Affiliation(s)
- Chenlu Wang
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China
| | - Qiqin Xu
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China
| | - Xianhong Zhang
- Hubei Key Laboratory of Cell Homeostasis, RNA Institute, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Daniel S Day
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA, 02142, USA
| | - Brian J Abraham
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA, 02142, USA
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Kehuan Lun
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China
| | - Liang Chen
- Hubei Key Laboratory of Cell Homeostasis, RNA Institute, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Jie Huang
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
| | - Xiong Ji
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
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20
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Mammalian PERIOD2 regulates H2A.Z incorporation in chromatin to orchestrate circadian negative feedback. Nat Struct Mol Biol 2022; 29:549-562. [PMID: 35606517 DOI: 10.1038/s41594-022-00777-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 04/11/2022] [Indexed: 11/08/2022]
Abstract
Mammalian circadian oscillators are built on a feedback loop in which the activity of the transcription factor CLOCK-BMAL1 is repressed by the PER-CRY complex. Here, we show that murine Per-/- fibroblasts display aberrant nucleosome occupancy around transcription start sites (TSSs) and at promoter-proximal and distal CTCF sites due to impaired histone H2A.Z deposition. Knocking out H2A.Z mimicked the Per null chromatin state and disrupted cellular rhythms. We found that endogenous mPER2 complexes retained CTCF as well as the specific H2A.Z-deposition chaperone YL1-a component of the ATP-dependent remodeler SRCAP and p400-TIP60 complex. While depleting YL1 or mutating chaperone-binding sites on H2A.Z lengthened the circadian period, H2A.Z deletion abrogated BMAL1 chromatin recruitment and promoted its proteasomal degradation. We propose that a PER2-mediated H2A.Z deposition pathway (1) compacts CLOCK-BMAL1 binding sites to establish negative feedback, (2) organizes circadian chromatin landscapes using CTCF and (3) bookmarks genomic loci for BMAL1 binding to impinge on the positive arm of the subsequent cycle.
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21
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Kreienbaum C, Paasche LW, Hake SB. H2A.Z's 'social' network: functional partners of an enigmatic histone variant. Trends Biochem Sci 2022; 47:909-920. [PMID: 35606214 DOI: 10.1016/j.tibs.2022.04.014] [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: 02/15/2022] [Revised: 04/14/2022] [Accepted: 04/26/2022] [Indexed: 11/25/2022]
Abstract
The histone variant H2A.Z has been extensively studied to understand its manifold DNA-based functions. In the past years, researchers identified its specific binding partners, the 'H2A.Z interactome', that convey H2A.Z-dependent chromatin changes. Here, we summarize the latest findings regarding vertebrate H2A.Z-associated factors and focus on their roles in gene activation and repression, cell cycle regulation, (neuro)development, and tumorigenesis. Additionally, we demonstrate how protein-protein interactions and post-translational histone modifications can fine-tune the complex interplay of H2A.Z-regulated gene expression. Last, we review the most recent results on interactors of the two isoforms H2A.Z.1 and H2A.Z.2.1, which differ in only three amino acids, and focus on cancer-associated mutations of H2A and H2A.Z, which reveal fascinating insights into the functional importance of such minuscule changes.
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Affiliation(s)
| | - Lena W Paasche
- Institute for Genetics, Justus-Liebig-University Giessen, Giessen, Germany
| | - Sandra B Hake
- Institute for Genetics, Justus-Liebig-University Giessen, Giessen, Germany.
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22
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Poyton MF, Feng XA, Ranjan A, Lei Q, Wang F, Zarb JS, Louder RK, Park G, Jo MH, Ye J, Liu S, Ha T, Wu C. Coordinated DNA and histone dynamics drive accurate histone H2A.Z exchange. SCIENCE ADVANCES 2022; 8:eabj5509. [PMID: 35263135 PMCID: PMC8906749 DOI: 10.1126/sciadv.abj5509] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
Nucleosomal histone H2A is exchanged for its variant H2A.Z by the SWR1 chromatin remodeler, but the mechanism and timing of histone exchange remain unclear. Here, we quantify DNA and histone dynamics during histone exchange in real time using a three-color single-molecule FRET assay. We show that SWR1 operates with timed precision to unwrap DNA with large displacement from one face of the nucleosome, remove H2A-H2B from the same face, and rewrap DNA, all within 2.3 s. This productive DNA unwrapping requires full SWR1 activation and differs from unproductive, smaller-scale DNA unwrapping caused by SWR1 binding alone. On an asymmetrically positioned nucleosome, SWR1 intrinsically senses long-linker DNA to preferentially exchange H2A.Z on the distal face as observed in vivo. The displaced H2A-H2B dimer remains briefly associated with the SWR1-nucleosome complex and is dissociated by histone chaperones. These findings reveal how SWR1 coordinates DNA unwrapping with histone dynamics to rapidly and accurately place H2A.Z at physiological sites on chromatin.
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Affiliation(s)
- Matthew F. Poyton
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Xinyu A. Feng
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
- Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA
| | - Anand Ranjan
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Qin Lei
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Feng Wang
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Jasmin S. Zarb
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Robert K. Louder
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Giho Park
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Myung Hyun Jo
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Joseph Ye
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Sheng Liu
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Howard Hughes Medical Institute, Baltimore, MD, USA
| | - Carl Wu
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, MD, USA
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23
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Whole-genome methods to define DNA and histone accessibility and long-range interactions in chromatin. Biochem Soc Trans 2022; 50:199-212. [PMID: 35166326 PMCID: PMC9847230 DOI: 10.1042/bst20210959] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/30/2021] [Accepted: 01/24/2022] [Indexed: 02/08/2023]
Abstract
Defining the genome-wide chromatin landscape has been a goal of experimentalists for decades. Here we review highlights of these efforts, from seminal experiments showing discontinuities in chromatin structure related to gene activation to extensions of these methods elucidating general features of chromatin related to gene states by exploiting deep sequencing methods. We also review chromatin conformational capture methods to identify patterns in long-range interactions between genomic loci.
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24
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Yang Y, Zhang L, Xiong C, Chen J, Wang L, Wen Z, Yu J, Chen P, Xu Y, Jin J, Cai Y, Li G. HIRA complex presets transcriptional potential through coordinating depositions of the histone variants H3.3 and H2A.Z on the poised genes in mESCs. Nucleic Acids Res 2022; 50:191-206. [PMID: 34893908 PMCID: PMC8754660 DOI: 10.1093/nar/gkab1221] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 11/26/2021] [Accepted: 11/30/2021] [Indexed: 12/21/2022] Open
Abstract
Histone variants have been implicated in regulating chromatin dynamics and genome functions. Previously, we have shown that histone variant H3.3 actively marks enhancers and cooperates with H2A.Z at promoters to prime the genes into a poised state in mouse embryonic stem cells (mESCs). However, how these two important histone variants collaboratively function in this process still remains elusive. In this study, we found that depletion of different components of HIRA complex, a specific chaperone of H3.3, results in significant decreases of H2A.Z enrichment at genome scale. In addition, CUT&Tag data revealed a genomic colocalization between HIRA complex and SRCAP complex. In vivo and in vitro biochemical assays verified that HIRA complex could interact with SRCAP complex through the Hira subunit. Furthermore, our chromatin accessibility and transcription analyses demonstrated that HIRA complex contributed to preset a defined chromatin feature around TSS region for poising gene transcription. In summary, our results unveiled that while regulating the H3.3 incorporation in the regulatory regions, HIRA complex also collaborates with SRCAP to deposit H2A.Z onto the promoters, which cooperatively determines the transcriptional potential of the poised genes in mESCs.
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Affiliation(s)
- Yang Yang
- School of Life Sciences, Jilin University, 2699 Qianjin Street, Changchun 130012, China
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Liwei Zhang
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Chaoyang Xiong
- 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
- Department of Immunology, School of Basic Medical Sciences, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing 100069, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Li Wang
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, 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, China
| | - Juan Yu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Ping Chen
- Department of Immunology, School of Basic Medical Sciences, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing 100069, China
| | - Yanhui Xu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Jingji Jin
- School of Life Sciences, Jilin University, 2699 Qianjin Street, Changchun 130012, China
- National Engineering Laboratory for AIDS Vaccine, Jilin University, 2699 Qianjin Street, Changchun 130012, China
- Key Laboratory for Molecular Enzymology and Engineering, The Ministry of Education, Jilin University, 2699 Qianjin Street, Changchun 130012, China
| | - Yong Cai
- School of Life Sciences, Jilin University, 2699 Qianjin Street, Changchun 130012, China
- National Engineering Laboratory for AIDS Vaccine, Jilin University, 2699 Qianjin Street, Changchun 130012, China
- Key Laboratory for Molecular Enzymology and Engineering, The Ministry of Education, Jilin University, 2699 Qianjin Street, Changchun 130012, 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, China
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Colino-Sanguino Y, Clark SJ, Valdes-Mora F. The H2A.Z-nuclesome code in mammals: emerging functions. Trends Genet 2021; 38:273-289. [PMID: 34702577 DOI: 10.1016/j.tig.2021.10.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/30/2021] [Accepted: 10/04/2021] [Indexed: 12/12/2022]
Abstract
H2A.Z is a histone variant that provides specific structural and docking-side properties to the nucleosome, resulting in diverse and specialised molecular and cellular functions. In this review, we discuss the latest studies uncovering new functional aspects of mammalian H2A.Z in gene transcription, including pausing and elongation of RNA polymerase II (RNAPII) and enhancer activity; DNA repair; DNA replication; and 3D chromatin structure. We also review the recently described role of H2A.Z in embryonic development, cell differentiation, neurodevelopment, and brain function. In conclusion, our cumulative knowledge of H2A.Z over the past 40 years, in combination with the implementation of novel molecular technologies, is unravelling an unexpected and complex role of histone variants in gene regulation and disease.
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Affiliation(s)
- Yolanda Colino-Sanguino
- Cancer Epigenetics Biology and Therapeutics, Precision Medicine Theme, Children's Cancer Institute, Sydney, NSW, Australia; School of Children and Women Health, University of NSW Sydney, Sydney, NSW, Australia.
| | - Susan J Clark
- Epigenetics Research Laboratory, Genomics and Epigenetics Division, Garvan Institute of Medical Research, Sydney, NSW, Australia; St. Vincent's Clinical School, University of NSW Sydney, Sydney, NSW, Australia
| | - Fatima Valdes-Mora
- Cancer Epigenetics Biology and Therapeutics, Precision Medicine Theme, Children's Cancer Institute, Sydney, NSW, Australia; School of Children and Women Health, University of NSW Sydney, Sydney, NSW, Australia.
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26
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Yuan Y, Cao W, Zhou H, Qian H, Wang H. H2A.Z acetylation by lincZNF337-AS1 via KAT5 implicated in the transcriptional misregulation in cancer signaling pathway in hepatocellular carcinoma. Cell Death Dis 2021; 12:609. [PMID: 34120148 PMCID: PMC8197763 DOI: 10.1038/s41419-021-03895-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 05/31/2021] [Accepted: 05/31/2021] [Indexed: 12/12/2022]
Abstract
In eukaryotes, histones and their variants are essential for chromatin structure and function; both play important roles in the regulation of gene transcription, as well as the development of tumors. We aimed to explore the genomics data of hepatocellular carcinoma (HCC), combined with literature analysis, in terms of the histone variant H2A.Z. Cell phenotype assay confirmed the effect of H2A.Z on the proliferation, metastasis, apoptosis, and cell cycle of HCC cells. H2A.Z was shown to function via the tumor dysregulation signaling pathway, with BCL6 as its interacting protein. In addition, the acetylation level of H2A.Z was higher in HCC and was related to tumor formation. We found the acetylation of H2A.Z to be related to and regulated by lincZNF337-AS1. LincZNF337-AS1 was found to bind to H2A.Z and KAT5 at different sites, promoting the acetylation of H2A.Z through KAT5. We concluded that, in HCC, H2A.Z is an oncogene, whose acetylation promotes the transcription of downstream genes, and is regulated by lincZNF331-AS1.
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Affiliation(s)
- Yin Yuan
- The Department of Hepatobiliary Surgery of Hospital Affiliated 5 to Nantong University(Taizhou People's Hospital), Taizhou, Jiangsu Province, China
| | - Wen Cao
- The Department of Liver Disease of Hospital Affiliated 5 to Nantong University(Taizhou People's Hospital), Taizhou, Jiangsu Province, China
| | - Hongbing Zhou
- The Department of Hepatobiliary Surgery of Hospital Affiliated 5 to Nantong University(Taizhou People's Hospital), Taizhou, Jiangsu Province, China
| | - Haixin Qian
- Department of General Surgery, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Honggang Wang
- The Department of General Surgery of Hospital Affiliated 5 to Nantong University(Taizhou People's Hospital), Taizhou, Jiangsu Province, China.
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At the Crossroad of Gene Regulation and Genome Organization: Potential Roles for ATP-Dependent Chromatin Remodelers in the Regulation of CTCF-Mediated 3D Architecture. BIOLOGY 2021; 10:biology10040272. [PMID: 33801596 PMCID: PMC8066914 DOI: 10.3390/biology10040272] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 03/20/2021] [Accepted: 03/25/2021] [Indexed: 02/07/2023]
Abstract
Simple Summary The way DNA is packaged in the nucleus of a cell is important for when and how genes are expressed. There are many levels of packaging, and new techniques have revealed that long-range interactions are important for both promoting and restricting the transcription of genes. Some long-range interactions are mediated by physical loops in the genome where, like a rubber band, the ring-shaped cohesin complex loops sections of DNA bound by CCCTC-binding factor (CTCF). Both cohesin and CTCF act on DNA, and increasing evidence indicates that their function is inhibited by nucleosomes bound to the DNA. In this review, we summarize the current knowledge of how individual chromatin remodelers, which utilize ATP to move nucleosomes on DNA, facilitate or inhibit cohesin/CTCF-dependent looping interactions. Abstract In higher order organisms, the genome is assembled into a protein-dense structure called chromatin. Chromatin is spatially organized in the nucleus through hierarchical folding, which is tightly regulated both in cycling cells and quiescent cells. Assembly and folding are not one-time events in a cell’s lifetime; rather, they are subject to dynamic shifts to allow changes in transcription, DNA replication, or DNA damage repair. Chromatin is regulated at many levels, and recent tools have permitted the elucidation of specific factors involved in the maintenance and regulation of the three-dimensional (3D) genome organization. In this review/perspective, we aim to cover the potential, but relatively unelucidated, crosstalk between 3D genome architecture and the ATP-dependent chromatin remodelers with a specific focus on how the architectural proteins CTCF and cohesin are regulated by chromatin remodeling.
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Scacchetti A, Becker PB. Variation on a theme: Evolutionary strategies for H2A.Z exchange by SWR1-type remodelers. Curr Opin Cell Biol 2020; 70:1-9. [PMID: 33217681 DOI: 10.1016/j.ceb.2020.10.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 10/16/2020] [Accepted: 10/19/2020] [Indexed: 01/08/2023]
Abstract
Histone variants are a universal means to alter the biochemical properties of nucleosomes, implementing local changes in chromatin structure. H2A.Z, one of the most conserved histone variants, is incorporated into chromatin by SWR1-type nucleosome remodelers. Here, we summarize recent advances toward understanding the transcription-regulatory roles of H2A.Z and of the remodeling enzymes that govern its dynamic chromatin incorporation. Tight transcriptional control guaranteed by H2A.Z nucleosomes depends on the context provided by other histone variants or chromatin modifications, such as histone acetylation. The functional cooperation of SWR1-type remodelers with NuA4 histone acetyltransferase complexes, a recurring theme during evolution, is structurally implemented by species-specific strategies.
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Affiliation(s)
- Alessandro Scacchetti
- Molecular Biology Division, Biomedical Center, Ludwig-Maximilians-Universität, Munich, Germany
| | - Peter B Becker
- Molecular Biology Division, Biomedical Center, Ludwig-Maximilians-Universität, Munich, Germany.
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