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Das A, Giri AK, Bhattacharjee P. Targeting 'histone mark': Advanced approaches in epigenetic regulation of telomere dynamics in cancer. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2024; 1867:195007. [PMID: 38237857 DOI: 10.1016/j.bbagrm.2024.195007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 01/23/2024]
Abstract
Telomere integrity is required for the maintenance of genome stability and prevention of oncogenic transformation of cells. Recent evidence suggests the presence of epigenetic modifications as an important regulator of mammalian telomeres. Telomeric and subtelomeric regions are rich in epigenetic marks that regulate telomere length majorly through DNA methylation and post-translational histone modifications. Specific histone modifying enzymes play an integral role in establishing telomeric histone codes necessary for the maintenance of structural integrity. Alterations of crucial histone moieties and histone modifiers cause deregulations in the telomeric chromatin leading to carcinogenic manifestations. This review delves into the significance of histone modifications and their influence on telomere dynamics concerning cancer. Additionally, it highlights the existing research gaps that hold the potential to drive the development of therapeutic interventions targeting the telomere epigenome.
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Affiliation(s)
- Ankita Das
- Department of Environmental Science, University of Calcutta, Kolkata 700019, India; Department of Zoology, University of Calcutta, Kolkata 700019, India
| | - Ashok K Giri
- Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Pritha Bhattacharjee
- Department of Environmental Science, University of Calcutta, Kolkata 700019, India.
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Brewis HT, Wang AY, Gaub A, Lau JJ, Stirling PC, Kobor MS. What makes a histone variant a variant: Changing H2A to become H2A.Z. PLoS Genet 2021; 17:e1009950. [PMID: 34871303 PMCID: PMC8675926 DOI: 10.1371/journal.pgen.1009950] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 12/16/2021] [Accepted: 11/16/2021] [Indexed: 01/01/2023] Open
Abstract
Chromatin structure and underlying DNA accessibility is modulated by the incorporation of histone variants. H2A.Z, a variant of the H2A core histone family, plays a distinct and essential role in a diverse set of biological functions including gene regulation and maintenance of heterochromatin-euchromatin boundaries. Although it is currently unclear how the replacement of H2A with H2A.Z can regulate gene expression, the variance in their amino acid sequence likely contributes to their functional differences. To tease apart regions of H2A.Z that confer its unique identity, a set of plasmids expressing H2A-H2A.Z hybrids from the native H2A.Z promoter were examined for their ability to recapitulate H2A.Z function. First, we found that the H2A.Z M6 region was necessary and sufficient for interaction with the SWR1-C chromatin remodeler. Remarkably, the combination of only 9 amino acid changes, the H2A.Z M6 region, K79 and L81 (two amino acids in the α2-helix), were sufficient to fully rescue growth phenotypes of the htz1Δ mutant. Furthermore, combining three unique H2A.Z regions (K79 and L81, M6, C-terminal tail) was sufficient for expression of H2A.Z-dependent heterochromatin-proximal genes and GAL1 derepression. Surprisingly, hybrid constructs that restored the transcription of H2A.Z-dependent genes, did not fully recapitulate patterns of H2A.Z-specific enrichment at the tested loci. This suggested that H2A.Z function in transcription regulation may be at least partially independent of its specific localization in chromatin. Together, this work has identified three regions that can confer specific H2A.Z-identity to replicative H2A, furthering our understanding of what makes a histone variant a variant.
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Affiliation(s)
- Hilary T. Brewis
- Centre for Molecular Medicine and Therapeutics, BC Children’s Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Alice Y. Wang
- Centre for Molecular Medicine and Therapeutics, BC Children’s Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Aline Gaub
- Centre for Molecular Medicine and Therapeutics, BC Children’s Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Justine J. Lau
- Centre for Molecular Medicine and Therapeutics, BC Children’s Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Peter C. Stirling
- Terry Fox Laboratory, BC Cancer, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Michael S. Kobor
- Centre for Molecular Medicine and Therapeutics, BC Children’s Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
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Yi SJ, Kim K. New Insights into the Role of Histone Changes in Aging. Int J Mol Sci 2020; 21:ijms21218241. [PMID: 33153221 PMCID: PMC7662996 DOI: 10.3390/ijms21218241] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/02/2020] [Accepted: 11/02/2020] [Indexed: 12/15/2022] Open
Abstract
Aging is the progressive decline or loss of function at the cellular, tissue, and organismal levels that ultimately leads to death. A number of external and internal factors, including diet, exercise, metabolic dysfunction, genome instability, and epigenetic imbalance, affect the lifespan of an organism. These aging factors regulate transcriptome changes related to the aging process through chromatin remodeling. Many epigenetic regulators, such as histone modification, histone variants, and ATP-dependent chromatin remodeling factors, play roles in chromatin reorganization. The key to understanding the role of gene regulatory networks in aging lies in characterizing the epigenetic regulators responsible for reorganizing and potentiating particular chromatin structures. This review covers epigenetic studies on aging, discusses the impact of epigenetic modifications on gene expression, and provides future directions in this area.
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Aristizabal MJ, Dever K, Negri GL, Shen M, Hawe N, Benschop JJ, Holstege FCP, Krogan NJ, Sadowski I, Kobor MS. Regulation of Skn7-dependent, oxidative stress-induced genes by the RNA polymerase II-CTD phosphatase, Fcp1, and Mediator kinase subunit, Cdk8, in yeast. J Biol Chem 2019; 294:16080-16094. [PMID: 31506296 DOI: 10.1074/jbc.ra119.008515] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 08/23/2019] [Indexed: 11/06/2022] Open
Abstract
Fcp1 is a protein phosphatase that facilitates transcription elongation and termination by dephosphorylating the C-terminal domain of RNA polymerase II. High-throughput genetic screening and gene expression profiling of fcp1 mutants revealed a novel connection to Cdk8, the Mediator complex kinase subunit, and Skn7, a key transcription factor in the oxidative stress response pathway. Briefly, Skn7 was enriched as a regulator of genes whose mRNA levels were altered in fcp1 and cdk8Δ mutants and was required for the suppression of fcp1 mutant growth defects by loss of CDK8 under oxidative stress conditions. Targeted analysis revealed that mutating FCP1 decreased Skn7 mRNA and protein levels as well as its association with target gene promoters but paradoxically increased the mRNA levels of Skn7-dependent oxidative stress-induced genes (TRX2 and TSA1) under basal and induced conditions. The latter was in part recapitulated via chemical inhibition of transcription in WT cells, suggesting that a combination of transcriptional and posttranscriptional effects underscored the increased mRNA levels of TRX2 and TSA1 observed in the fcp1 mutant. Interestingly, loss of CDK8 robustly normalized the mRNA levels of Skn7-dependent genes in the fcp1 mutant background and also increased Skn7 protein levels by preventing its turnover. As such, our work suggested that loss of CDK8 could overcome transcriptional and/or posttranscriptional alterations in the fcp1 mutant through its regulatory effect on Skn7. Furthermore, our work also implicated FCP1 and CDK8 in the broader response to environmental stressors in yeast.
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Affiliation(s)
- Maria J Aristizabal
- Centre for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario M5S 3B2, Canada.,Child and Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario M5G 1Z8, Canada
| | - Kristy Dever
- Centre for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Gian Luca Negri
- Canada's Michael Smith Genome Sciences Centre, BC Cancer, Vancouver V5Z 1L3, British Columbia, Canada
| | - Mary Shen
- Centre for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Nicole Hawe
- Department of Biochemistry and Molecular Biology, Molecular Epigenetics, Life Sciences Institute, University of British Columbia, Vancouver V6T 1Z3, British Columbia, Canada
| | - Joris J Benschop
- Princess Máxima Center for Pediatric Oncology, Heidelberglaan 25, 3584 CS Utrecht, The Netherlands
| | - Frank C P Holstege
- Princess Máxima Center for Pediatric Oncology, Heidelberglaan 25, 3584 CS Utrecht, The Netherlands
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94158
| | - Ivan Sadowski
- Department of Biochemistry and Molecular Biology, Molecular Epigenetics, Life Sciences Institute, University of British Columbia, Vancouver V6T 1Z3, British Columbia, Canada
| | - Michael S Kobor
- Centre for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
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Aristizabal MJ, Negri GL, Kobor MS. The RNAPII-CTD Maintains Genome Integrity through Inhibition of Retrotransposon Gene Expression and Transposition. PLoS Genet 2015; 11:e1005608. [PMID: 26496706 PMCID: PMC4619828 DOI: 10.1371/journal.pgen.1005608] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 09/27/2015] [Indexed: 12/14/2022] Open
Abstract
RNA polymerase II (RNAPII) contains a unique C-terminal domain that is composed of heptapeptide repeats and which plays important regulatory roles during gene expression. RNAPII is responsible for the transcription of most protein-coding genes, a subset of non-coding genes, and retrotransposons. Retrotransposon transcription is the first step in their multiplication cycle, given that the RNA intermediate is required for the synthesis of cDNA, the material that is ultimately incorporated into a new genomic location. Retrotransposition can have grave consequences to genome integrity, as integration events can change the gene expression landscape or lead to alteration or loss of genetic information. Given that RNAPII transcribes retrotransposons, we sought to investigate if the RNAPII-CTD played a role in the regulation of retrotransposon gene expression. Importantly, we found that the RNAPII-CTD functioned to maintaining genome integrity through inhibition of retrotransposon gene expression, as reducing CTD length significantly increased expression and transposition rates of Ty1 elements. Mechanistically, the increased Ty1 mRNA levels in the rpb1-CTD11 mutant were partly due to Cdk8-dependent alterations to the RNAPII-CTD phosphorylation status. In addition, Cdk8 alone contributed to Ty1 gene expression regulation by altering the occupancy of the gene-specific transcription factor Ste12. Loss of STE12 and TEC1 suppressed growth phenotypes of the RNAPII-CTD truncation mutant. Collectively, our results implicate Ste12 and Tec1 as general and important contributors to the Cdk8, RNAPII-CTD regulatory circuitry as it relates to the maintenance of genome integrity.
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Affiliation(s)
- Maria J. Aristizabal
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Gian Luca Negri
- Department of Molecular Oncology, BC Cancer Research Center, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael S. Kobor
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
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Dvořáčková M, Fojtová M, Fajkus J. Chromatin dynamics of plant telomeres and ribosomal genes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 83:18-37. [PMID: 25752316 DOI: 10.1111/tpj.12822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/03/2015] [Accepted: 03/03/2015] [Indexed: 05/03/2023]
Abstract
Telomeres and genes encoding 45S ribosomal RNA (rDNA) are frequently located adjacent to each other on eukaryotic chromosomes. Although their primary roles are different, they show striking similarities with respect to their features and additional functions. Both genome domains have remarkably dynamic chromatin structures. Both are hypersensitive to dysfunctional histone chaperones, responding at the genomic and epigenomic levels. Both generate non-coding transcripts that, in addition to their epigenetic roles, may induce gross chromosomal rearrangements. Both give rise to chromosomal fragile sites, as their replication is intrinsically problematic. However, at the same time, both are essential for maintenance of genomic stability and integrity. Here we discuss the structural and functional inter-connectivity of telomeres and rDNA, with a focus on recent results obtained in plants.
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Affiliation(s)
- Martina Dvořáčková
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Kamenice 5, 62500, Brno, Czech Republic
- Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic
| | - Miloslava Fojtová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Kamenice 5, 62500, Brno, Czech Republic
- Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Kamenice 5, 62500, Brno, Czech Republic
- Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic
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