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Ghimire P, Motamedi M, Joh R. Mathematical model for the role of multiple pericentromeric repeats on heterochromatin assembly. PLoS Comput Biol 2024; 20:e1012027. [PMID: 38598558 PMCID: PMC11034663 DOI: 10.1371/journal.pcbi.1012027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 04/22/2024] [Accepted: 03/27/2024] [Indexed: 04/12/2024] Open
Abstract
Although the length and constituting sequences for pericentromeric repeats are highly variable across eukaryotes, the presence of multiple pericentromeric repeats is one of the conserved features of the eukaryotic chromosomes. Pericentromeric heterochromatin is often misregulated in human diseases, with the expansion of pericentromeric repeats in human solid cancers. In this article, we have developed a mathematical model of the RNAi-dependent methylation of H3K9 in the pericentromeric region of fission yeast. Our model, which takes copy number as an explicit parameter, predicts that the pericentromere is silenced only if there are many copies of repeats. It becomes bistable or desilenced if the copy number of repeats is reduced. This suggests that the copy number of pericentromeric repeats alone can determine the fate of heterochromatin silencing in fission yeast. Through sensitivity analysis, we identified parameters that favor bistability and desilencing. Stochastic simulation shows that faster cell division and noise favor the desilenced state. These results show the unexpected role of pericentromeric repeat copy number in gene silencing and provide a quantitative basis for how the copy number allows or protects repetitive and unique parts of the genome from heterochromatin silencing, respectively.
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Affiliation(s)
- Puranjan Ghimire
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Mo Motamedi
- Massachusetts General Hospital Center for Cancer Research and Department of Medicine, Harvard Medical School, Charlestown, Boston, Massachusetts, United States of America
| | - Richard Joh
- Department of Physics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Massey Cancer Center, Virginia Commonwealth University, Richmond Virginia, United States of America
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Sidhwani P, Straight AF. Epigenetic inheritance and boundary maintenance at human centromeres. Curr Opin Struct Biol 2023; 82:102694. [PMID: 37657353 PMCID: PMC10530090 DOI: 10.1016/j.sbi.2023.102694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 07/31/2023] [Accepted: 08/07/2023] [Indexed: 09/03/2023]
Abstract
Centromeres are chromosomal regions that provide the foundation for microtubule attachment during chromosome segregation. Centromeres are epigenetically defined by nucleosomes containing the histone H3 variant centromere protein A (CENP-A) and, in many organisms, are surrounded by transcriptionally repressed pericentromeric chromatin marked by trimethylation of histone H3 lysine 9 (H3K9me3). Pericentromeric regions facilitate sister chromatid cohesion during mitosis, thereby supporting centromere function. Heterochromatin has a known propensity to spread into adjacent euchromatic domains unless it is properly bounded. Heterochromatin spreading into the centromere can disrupt kinetochore function, perturbing chromosome segregation and genome stability. In the fission yeast Schizosaccharomyces pombe, tRNA genes provide barriers to heterochromatin spread at the centromere, the absence of which results in abnormal meiotic chromosome segregation. How heterochromatin-centromere boundaries are established in humans is not understood. We propose models for stable epigenetic inheritance of centromeric domains in humans and discuss advances that will enable the discovery of novel regulators of this process.
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Affiliation(s)
- Pragya Sidhwani
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States. https://twitter.com/@pra_sidh
| | - Aaron F Straight
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States.
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Grewal SIS. The molecular basis of heterochromatin assembly and epigenetic inheritance. Mol Cell 2023; 83:1767-1785. [PMID: 37207657 PMCID: PMC10309086 DOI: 10.1016/j.molcel.2023.04.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 04/10/2023] [Accepted: 04/20/2023] [Indexed: 05/21/2023]
Abstract
Heterochromatin plays a fundamental role in gene regulation, genome integrity, and silencing of repetitive DNA elements. Histone modifications are essential for the establishment of heterochromatin domains, which is initiated by the recruitment of histone-modifying enzymes to nucleation sites. This leads to the deposition of histone H3 lysine-9 methylation (H3K9me), which provides the foundation for building high-concentration territories of heterochromatin proteins and the spread of heterochromatin across extended domains. Moreover, heterochromatin can be epigenetically inherited during cell division in a self-templating manner. This involves a "read-write" mechanism where pre-existing modified histones, such as tri-methylated H3K9 (H3K9me3), support chromatin association of the histone methyltransferase to promote further deposition of H3K9me. Recent studies suggest that a critical density of H3K9me3 and its associated factors is necessary for the propagation of heterochromatin domains across multiple generations. In this review, I discuss the key experiments that have highlighted the importance of modified histones for epigenetic inheritance.
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Affiliation(s)
- Shiv I S Grewal
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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Lam UTF, Tan BKY, Poh JJX, Chen ES. Structural and functional specificity of H3K36 methylation. Epigenetics Chromatin 2022; 15:17. [PMID: 35581654 PMCID: PMC9116022 DOI: 10.1186/s13072-022-00446-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 04/04/2022] [Indexed: 12/20/2022] Open
Abstract
The methylation of histone H3 at lysine 36 (H3K36me) is essential for maintaining genomic stability. Indeed, this methylation mark is essential for proper transcription, recombination, and DNA damage response. Loss- and gain-of-function mutations in H3K36 methyltransferases are closely linked to human developmental disorders and various cancers. Structural analyses suggest that nucleosomal components such as the linker DNA and a hydrophobic patch constituted by histone H2A and H3 are likely determinants of H3K36 methylation in addition to the histone H3 tail, which encompasses H3K36 and the catalytic SET domain. Interaction of H3K36 methyltransferases with the nucleosome collaborates with regulation of their auto-inhibitory changes fine-tunes the precision of H3K36me in mediating dimethylation by NSD2 and NSD3 as well as trimethylation by Set2/SETD2. The identification of specific structural features and various cis-acting factors that bind to different forms of H3K36me, particularly the di-(H3K36me2) and tri-(H3K36me3) methylated forms of H3K36, have highlighted the intricacy of H3K36me functional significance. Here, we consolidate these findings and offer structural insight to the regulation of H3K36me2 to H3K36me3 conversion. We also discuss the mechanisms that underlie the cooperation between H3K36me and other chromatin modifications (in particular, H3K27me3, H3 acetylation, DNA methylation and N6-methyladenosine in RNAs) in the physiological regulation of the epigenomic functions of chromatin.
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Affiliation(s)
- Ulysses Tsz Fung Lam
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Bryan Kok Yan Tan
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - John Jia Xin Poh
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Ee Sin Chen
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. .,National University Health System (NUHS), Singapore, Singapore. .,NUS Center for Cancer Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. .,Integrative Sciences & Engineering Programme, National University of Singapore, Singapore, Singapore.
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Barbosa P, Schemczssen-Graeff Z, Marques A, da Silva M, Favero GM, Sobreiro BP, de Almeida MC, Moreira-Filho O, Silva DMZDA, Porto-Foresti F, Foresti F, Artoni RF. Silencing of Transposable Elements Mediated by 5-mC and Compensation of the Heterochromatin Content by Presence of B Chromosomes in Astyanax scabripinnis. Cells 2021; 10:1162. [PMID: 34064768 PMCID: PMC8151356 DOI: 10.3390/cells10051162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Revised: 04/30/2021] [Accepted: 05/04/2021] [Indexed: 01/21/2023] Open
Abstract
The way in which transcriptional activity overcomes the physical DNA structure and gene regulation mechanisms involves complex processes that are not yet fully understood. Modifications in the cytosine-guanine sequence of DNA by 5-mC are preferentially located in heterochromatic regions and are related to gene silencing. Herein, we investigate evidence of epigenetic regulation related to the B chromosome model and transposable elements in A. scabripinnis. Indirect immunofluorescence using anti-5-mC to mark methylated regions was employed along with quantitative ELISA to determine the total genomic DNA methylation level. 5-mC signals were dispersed in the chromosomes of both females and males, with preferential accumulation in the B chromosome. In addition to the heterochromatic methylated regions, our results suggest that methylation is associated with transposable elements (LINE and Tc1-Mariner). Heterochromatin content was measured based on the C-band length in relation to the size of chromosome 1. The B chromosome in A. scabripinnis comprises heterochromatin located in the pericentromeric region of both arms of this isochromosome. In this context, individuals with B chromosomes should have an increased heterochromatin content when compared to individuals that do not. Although, both heterochromatin content and genome methylation showed no significant differences between sexes or in relation to the occurrence of B chromosomes. Our evidence suggests that the B chromosome can have a compensation effect on the heterochromatin content and that methylation possibly operates to silence TEs in A. scabripinnis. This represents a sui generis compensation and gene activity buffering mechanism.
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Affiliation(s)
- Patrícia Barbosa
- Post Graduate Program in Evolutionary Genetics and Molecular Biology, Department of Genetics and Evolution, Federal University of São Carlos, Rodovia Washington Luís Km 235, São Carlos 13565-905, SP, Brazil; (P.B.); (O.M.-F.)
| | - Zelinda Schemczssen-Graeff
- Post Graduate Program in Evolutionary Biology, Department of Structural, Molecular and Genetic Biology, State University of Ponta Grossa, Avenida Carlos Cavalcanti 4748, Ponta Grossa 84030-900, PR, Brazil; (Z.S.-G.); (M.d.S.); (M.C.d.A.)
| | - André Marques
- Department of Botany, Federal University of Pernambuco, Recife 50670-901, PE, Brazil;
| | - Maelin da Silva
- Post Graduate Program in Evolutionary Biology, Department of Structural, Molecular and Genetic Biology, State University of Ponta Grossa, Avenida Carlos Cavalcanti 4748, Ponta Grossa 84030-900, PR, Brazil; (Z.S.-G.); (M.d.S.); (M.C.d.A.)
| | - Giovani Marino Favero
- Department of General Biology, State University of Ponta Grossa, Avenida Carlos Cavalcanti 4748, Ponta Grossa 84030-900, PR, Brazil;
| | - Bernardo Passos Sobreiro
- Department of Medicine, State University of Ponta Grossa, Avenida Carlos Cavalcanti 4748, Ponta Grossa 84030-900, PR, Brazil;
| | - Mara Cristina de Almeida
- Post Graduate Program in Evolutionary Biology, Department of Structural, Molecular and Genetic Biology, State University of Ponta Grossa, Avenida Carlos Cavalcanti 4748, Ponta Grossa 84030-900, PR, Brazil; (Z.S.-G.); (M.d.S.); (M.C.d.A.)
| | - Orlando Moreira-Filho
- Post Graduate Program in Evolutionary Genetics and Molecular Biology, Department of Genetics and Evolution, Federal University of São Carlos, Rodovia Washington Luís Km 235, São Carlos 13565-905, SP, Brazil; (P.B.); (O.M.-F.)
| | - Duílio Mazzoni Zerbinato de Andrade Silva
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, Sao Paulo State University (UNESP), Botucatu 18618-689, SP, Brazil; (D.M.Z.d.A.S.); (F.F.)
| | - Fábio Porto-Foresti
- Faculty of Sciences, Sao Paulo State University (UNESP), Bauru 01049-010, SP, Brazil;
| | - Fausto Foresti
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, Sao Paulo State University (UNESP), Botucatu 18618-689, SP, Brazil; (D.M.Z.d.A.S.); (F.F.)
| | - Roberto Ferreira Artoni
- Post Graduate Program in Evolutionary Genetics and Molecular Biology, Department of Genetics and Evolution, Federal University of São Carlos, Rodovia Washington Luís Km 235, São Carlos 13565-905, SP, Brazil; (P.B.); (O.M.-F.)
- Post Graduate Program in Evolutionary Biology, Department of Structural, Molecular and Genetic Biology, State University of Ponta Grossa, Avenida Carlos Cavalcanti 4748, Ponta Grossa 84030-900, PR, Brazil; (Z.S.-G.); (M.d.S.); (M.C.d.A.)
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Fission Yeast Methylenetetrahydrofolate Reductase Ensures Mitotic and Meiotic Chromosome Segregation Fidelity. Int J Mol Sci 2021; 22:ijms22020639. [PMID: 33440639 PMCID: PMC7827777 DOI: 10.3390/ijms22020639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 01/05/2021] [Indexed: 12/17/2022] Open
Abstract
Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the folate metabolic pathway, and its loss of function through polymorphisms is often associated with human conditions, including cancer, congenital heart disease, and Down syndrome. MTHFR is also required in the maintenance of heterochromatin, a crucial determinant of genomic stability and precise chromosomal segregation. Here, we characterize the function of a fission yeast gene met11+, which encodes a protein that is highly homologous to the mammalian MTHFR. We show that, although met11+ is not essential for viability, its disruption increases chromosome missegregation and destabilizes constitutive heterochromatic regions at pericentromeric, sub-telomeric and ribosomal DNA (rDNA) loci. Transcriptional silencing at these sites were disrupted, which is accompanied by the reduction in enrichment of histone H3 lysine 9 dimethylation (H3K9me2) and binding of the heterochromatin protein 1 (HP1)-like Swi6. The met11 null mutant also dominantly disrupts meiotic fidelity, as displayed by reduced sporulation efficiency and defects in proper partitioning of the genetic material during meiosis. Interestingly, the faithful execution of these meiotic processes is synergistically ensured by cooperation among Met11, Rec8, a meiosis-specific cohesin protein, and the shugoshin protein Sgo1, which protects Rec8 from untimely cleavage. Overall, our results suggest a key role for Met11 in maintaining pericentromeric heterochromatin for precise genetic inheritance during mitosis and meiosis.
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Wu SK, Roberts JT, Balas MM, Johnson AM. RNA matchmaking in chromatin regulation. Biochem Soc Trans 2020; 48:2467-2481. [PMID: 33245317 PMCID: PMC7888525 DOI: 10.1042/bst20191225] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/05/2020] [Accepted: 10/07/2020] [Indexed: 01/12/2023]
Abstract
Beyond being the product of gene expression, RNA can also influence the regulation of chromatin. The majority of the human genome has the capacity to be transcribed and the majority of the non-protein-coding transcripts made by RNA Polymerase II are enriched in the nucleus. Many chromatin regulators can bind to these ncRNAs in the nucleus; in some cases, there are clear examples of direct RNA-mediated chromatin regulation mechanisms stemming from these interactions, while others have yet to be determined. Recent studies have highlighted examples of chromatin regulation via RNA matchmaking, a term we use broadly here to describe intermolecular base-pairing interactions between one RNA molecule and an RNA or DNA match. This review provides examples of RNA matchmaking that regulates chromatin processes and summarizes the technical approaches used to capture these events.
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Affiliation(s)
- Stephen K. Wu
- Molecular Biology Program, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
| | - Justin T. Roberts
- Molecular Biology Program, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
| | - Maggie M. Balas
- Molecular Biology Program, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
| | - Aaron M. Johnson
- Molecular Biology Program, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver Anschutz Medical Campus 12801 East 17 Ave., Aurora, CO, United States
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Arunkumar G, Melters DP. Centromeric Transcription: A Conserved Swiss-Army Knife. Genes (Basel) 2020; 11:E911. [PMID: 32784923 PMCID: PMC7463856 DOI: 10.3390/genes11080911] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/05/2020] [Accepted: 08/07/2020] [Indexed: 12/11/2022] Open
Abstract
In most species, the centromere is comprised of repetitive DNA sequences, which rapidly evolve. Paradoxically, centromeres fulfill an essential function during mitosis, as they are the chromosomal sites wherein, through the kinetochore, the mitotic spindles bind. It is now generally accepted that centromeres are transcribed, and that such transcription is associated with a broad range of functions. More than a decade of work on this topic has shown that centromeric transcripts are found across the eukaryotic tree and associate with heterochromatin formation, chromatin structure, kinetochore structure, centromeric protein loading, and inner centromere signaling. In this review, we discuss the conservation of small and long non-coding centromeric RNAs, their associations with various centromeric functions, and their potential roles in disease.
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Affiliation(s)
| | - Daniël P. Melters
- Chromatin Structure and Epigenetic Mechanisms, Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892, USA;
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Shen KF, Forsburg SL. Overlapping Roles in Chromosome Segregation for Heterochromatin Protein 1 (Swi6) and DDK in Schizosaccharomyces pombe. Genetics 2019; 212:417-430. [PMID: 31000521 PMCID: PMC6553818 DOI: 10.1534/genetics.119.302125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 04/10/2019] [Indexed: 12/23/2022] Open
Abstract
Fission yeast Swi6 is a human HP1 homolog that plays important roles in multiple cellular processes. In addition to its role in maintaining heterochromatin silencing, Swi6 is required for cohesin enrichment at the pericentromere. Loss of Swi6 leads to abnormal mitosis, including defects in the establishment of bioriented sister kinetochores and microtubule attachment. Swi6 interacts with Dfp1, a regulatory subunit of DBF4-dependent kinase (DDK), and failure to recruit Dfp1 to the pericentromere results in late DNA replication. Using the dfp1-3A mutant allele, which specifically disrupts Swi6-Dfp1 association, we investigated how interaction between Swi6 and Dfp1 affects chromosome dynamics. We find that disrupting the interaction between Swi6 and Dfp1 delays mitotic progression in a spindle assembly checkpoint-dependent manner. Artificially tethering Dfp1 back to the pericentromere is sufficient to restore normal spindle length and rescue segregation defects in swi6-deleted cells. However, Swi6 is necessary for centromeric localization of Rad21-GFP independent of DDK. Our data indicate that DDK contributes to mitotic chromosome segregation in pathways that partly overlap with, but can be separated from both, Swi6 and the other HP1 homolog, Chp2.
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Affiliation(s)
- Kuo-Fang Shen
- Program in Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089-2910
| | - Susan L Forsburg
- Program in Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089-2910
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A Heterochromatin Domain Forms Gradually at a New Telomere and Is Dynamic at Stable Telomeres. Mol Cell Biol 2018; 38:MCB.00393-17. [PMID: 29784772 PMCID: PMC6048312 DOI: 10.1128/mcb.00393-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 05/09/2018] [Indexed: 02/03/2023] Open
Abstract
Heterochromatin domains play important roles in chromosome biology, organismal development, and aging, including centromere function, mammalian female X chromosome inactivation, and senescence-associated heterochromatin foci. In the fission yeast Schizosaccharomyces pombe and metazoans, heterochromatin contains histone H3 that is dimethylated at lysine 9. Heterochromatin domains play important roles in chromosome biology, organismal development, and aging, including centromere function, mammalian female X chromosome inactivation, and senescence-associated heterochromatin foci. In the fission yeast Schizosaccharomyces pombe and metazoans, heterochromatin contains histone H3 that is dimethylated at lysine 9. While factors required for heterochromatin have been identified, the dynamics of heterochromatin formation are poorly understood. Telomeres convert adjacent chromatin into heterochromatin. To form a new heterochromatic region in S. pombe, an inducible DNA double-strand break (DSB) was engineered next to 48 bp of telomere repeats in euchromatin, which caused formation of a new telomere and the establishment and gradual spreading of a new heterochromatin domain. However, spreading was dynamic even after the telomere had reached its stable length, with reporter genes within the heterochromatin domain showing variegated expression. The system also revealed the presence of repeats located near the boundaries of euchromatin and heterochromatin that are oriented to allow the efficient healing of a euchromatic DSB to cap the chromosome end with a new telomere. Telomere formation in S. pombe therefore reveals novel aspects of heterochromatin dynamics and fail-safe mechanisms to repair subtelomeric breaks, with implications for similar processes in metazoan genomes.
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Kato H, Okazaki K, Urano T. How does Hsp90 function in RNAi-dependent heterochromatin assembly? Curr Genet 2018; 65:87-91. [PMID: 29974204 DOI: 10.1007/s00294-018-0866-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 07/01/2018] [Accepted: 07/01/2018] [Indexed: 12/16/2022]
Abstract
Heat-shock protein 90 (Hsp90) was recently identified as a silencing factor required for RNA interference (RNAi)-dependent heterochromatin assembly in the fission yeast Schizosaccharomyces pombe. As Hsp90 is known to contribute to the formation of small RNA-containing effector complexes, it would be expected that Hsp90 is also involved in the RNAi pathway in fission yeast. However, upon investigation, we found it very difficult to determine how Hsp90 modulates RNAi-dependent heterochromatin assembly in the cell. A lack of detectable small interfering RNAs in hsp90 mutant cells prevented us from examining the role of Hsp90 in the siRNA loading in the cell. In addition, deletion of genes encoding co-chaperones for Hsp90 appears not to affect RNAi-dependent pericentromeric silencing. One possible approach for elucidating the role of Hsp90 in RNAi-dependent heterochromatin assembly is the use of forward genetic screens to identify novel factors linking Hsp90 with other known RNAi factors. Here, we discuss the benefits of conducting further screenings and present some technical hints to help identify new factors.
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Affiliation(s)
- Hiroaki Kato
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya-cho, Izumo, 693-8501, Japan.
| | - Kosuke Okazaki
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya-cho, Izumo, 693-8501, Japan.,KNC Laboratories Co. Ltd., Kobe, Hyogo, 651-2271, Japan
| | - Takeshi Urano
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya-cho, Izumo, 693-8501, Japan
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Okazaki K, Kato H, Iida T, Shinmyozu K, Nakayama JI, Murakami Y, Urano T. RNAi-dependent heterochromatin assembly in fission yeast Schizosaccharomyces pombe requires heat-shock molecular chaperones Hsp90 and Mas5. Epigenetics Chromatin 2018; 11:26. [PMID: 29866182 PMCID: PMC5985592 DOI: 10.1186/s13072-018-0199-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Accepted: 05/31/2018] [Indexed: 11/28/2022] Open
Abstract
Background Heat-shock molecular chaperone proteins (Hsps) promote the loading of small interfering RNA (siRNA) onto RNA interference (RNAi) effector complexes. While the RNAi process is coupled with heterochromatin assembly in several model organisms, it remains unclear whether the Hsps contribute to epigenetic gene regulation. In this study, we used the fission yeast Schizosaccharomyces pombe as a model organism and investigated the roles of Hsp90 and Mas5 (a nucleocytoplasmic type-I Hsp40 protein) in RNAi-dependent heterochromatin assembly. Results Using a genetic screen and biochemical analyses, we identified Hsp90 and Mas5 as novel silencing factors. Mutations in the genes encoding these factors caused derepression of silencing at the pericentromere, where heterochromatin is assembled in an RNAi-dependent manner, but not at the subtelomere, where RNAi is dispensable. The mutations also caused a substantial reduction in the level of dimethylation of histone H3 at Lys9 at the pericentromere, where association of the Argonaute protein Ago1 was also abrogated. Consistently, siRNA corresponding to the pericentromeric repeats was undetectable in these mutant cells. In addition, levels of Tas3, which is a protein in the RNA-induced transcriptional silencing complex along with Ago1, were reduced in the absence of Mas5. Conclusions Our results suggest that the Hsps Hsp90 and Mas5 contribute to RNAi-dependent heterochromatin assembly. In particular, Mas5 appears to be required to stabilize Tas3 in vivo. We infer that impairment of Hsp90 and Hsp40 also may affect the integrity of the epigenome in other organisms. Electronic supplementary material The online version of this article (10.1186/s13072-018-0199-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kosuke Okazaki
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya-cho, Izumo, Shimane, 693-8501, Japan.,KNC Laboratories Co. Ltd., Kobe, Hyogo, 651-2271, Japan
| | - Hiroaki Kato
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya-cho, Izumo, Shimane, 693-8501, Japan.
| | - Tetsushi Iida
- Division of Cytogenetics, National Institute of Genetics, Mishima, 1111 Yata, Mishima, 411-8540, Japan.,Laboratory for Genome Regeneration, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Kaori Shinmyozu
- Proteomics Support Unit, RIKEN Center for Developmental Biology, Kobe, Hyogo, 650-0047, Japan.,National Cerebral and Cardiovascular Center, Suita, Osaka, 565-8565, Japan
| | - Jun-Ichi Nakayama
- Division of Chromatin Regulation, National Institute for Basic Biology, Okazaki, Aichi, 444-8585, Japan
| | - Yota Murakami
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
| | - Takeshi Urano
- Department of Biochemistry, Shimane University School of Medicine, 89-1 Enya-cho, Izumo, Shimane, 693-8501, Japan
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Kim HM, Beese-Sims SE, Colaiácovo MP. Fanconi Anemia FANCM/FNCM-1 and FANCD2/FCD-2 Are Required for Maintaining Histone Methylation Levels and Interact with the Histone Demethylase LSD1/SPR-5 in Caenorhabditis elegans. Genetics 2018; 209:409-423. [PMID: 29588287 PMCID: PMC5972417 DOI: 10.1534/genetics.118.300823] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 03/22/2018] [Indexed: 11/18/2022] Open
Abstract
The histone demethylase LSD1 was originally discovered by removing methyl groups from di- and monomethylated histone H3 lysine 4 (H3K4me2/1). Several studies suggest that LSD1 plays roles in meiosis as well as in the epigenetic regulation of fertility given that, in its absence, there is evidence of a progressive accumulation of H3K4me2 and increased sterility through generations. In addition to the progressive sterility phenotype observed in the mutants, growing evidence for the importance of histone methylation in the regulation of DNA damage repair has attracted more attention to the field in recent years. However, we are still far from understanding the mechanisms by which histone methylation is involved in DNA damage repair, and only a few studies have focused on the roles of histone demethylases in germline maintenance. Here, we show that the histone demethylase LSD1/CeSPR-5 interacts with the Fanconi anemia (FA) protein FANCM/CeFNCM-1 using biochemical, cytological, and genetic analyses. LSD1/CeSPR-5 is required for replication stress-induced S phase-checkpoint activation, and its absence suppresses the embryonic lethality and larval arrest observed in fncm-1 mutants. FANCM/CeFNCM-1 relocalizes upon hydroxyurea exposure and colocalizes with FANCD2/CeFCD-2 and LSD1/CeSPR-5, suggesting coordination between this histone demethylase and FA components to resolve replication stress. Surprisingly, the FA pathway is required for H3K4me2 maintenance, regardless of the presence of replication stress. Our study reveals a connection between FA and epigenetic maintenance and therefore provides new mechanistic insight into the regulation of histone methylation in DNA repair.
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Affiliation(s)
- Hyun-Min Kim
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
- School of Pharmaceutical Science and Technology, Tianjin University, 300072, China
| | - Sara E Beese-Sims
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
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15
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Schalch T, Steiner FA. Structure of centromere chromatin: from nucleosome to chromosomal architecture. Chromosoma 2017; 126:443-455. [PMID: 27858158 PMCID: PMC5509776 DOI: 10.1007/s00412-016-0620-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 11/09/2016] [Accepted: 11/10/2016] [Indexed: 12/14/2022]
Abstract
The centromere is essential for the segregation of chromosomes, as it serves as attachment site for microtubules to mediate chromosome segregation during mitosis and meiosis. In most organisms, the centromere is restricted to one chromosomal region that appears as primary constriction on the condensed chromosome and is partitioned into two chromatin domains: The centromere core is characterized by the centromere-specific histone H3 variant CENP-A (also called cenH3) and is required for specifying the centromere and for building the kinetochore complex during mitosis. This core region is generally flanked by pericentric heterochromatin, characterized by nucleosomes containing H3 methylated on lysine 9 (H3K9me) that are bound by heterochromatin proteins. During mitosis, these two domains together form a three-dimensional structure that exposes CENP-A-containing chromatin to the surface for interaction with the kinetochore and microtubules. At the same time, this structure supports the tension generated during the segregation of sister chromatids to opposite poles. In this review, we discuss recent insight into the characteristics of the centromere, from the specialized chromatin structures at the centromere core and the pericentromere to the three-dimensional organization of these regions that make up the functional centromere.
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Affiliation(s)
- Thomas Schalch
- Department of Molecular Biology, Sciences III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland.
| | - Florian A Steiner
- Department of Molecular Biology, Sciences III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland.
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16
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Job G, Brugger C, Xu T, Lowe BR, Pfister Y, Qu C, Shanker S, Baños Sanz JI, Partridge JF, Schalch T. SHREC Silences Heterochromatin via Distinct Remodeling and Deacetylation Modules. Mol Cell 2017; 62:207-221. [PMID: 27105116 DOI: 10.1016/j.molcel.2016.03.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/27/2016] [Accepted: 03/11/2016] [Indexed: 11/18/2022]
Abstract
Nucleosome remodeling and deacetylation (NuRD) complexes are co-transcriptional regulators implicated in differentiation, development, and diseases. Methyl-CpG binding domain (MBD) proteins play an essential role in recruitment of NuRD complexes to their target sites in chromatin. The related SHREC complex in fission yeast drives transcriptional gene silencing in heterochromatin through cooperation with HP1 proteins. How remodeler and histone deacetylase (HDAC) cooperate within NuRD complexes remains unresolved. We determined that in SHREC the two modules occupy distant sites on the scaffold protein Clr1 and that repressive activity of SHREC can be modulated by the expression level of the HDAC-associated Clr1 domain alone. Moreover, the crystal structure of Clr2 reveals an MBD-like domain mediating recruitment of the HDAC module to heterochromatin. Thus, SHREC bi-functionality is organized in two separate modules with separate recruitment mechanisms, which work together to elicit transcriptional silencing at heterochromatic loci.
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Affiliation(s)
- Godwin Job
- Department of Pathology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Christiane Brugger
- Department of Molecular Biology, Science III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 1211 Geneva 4, Switzerland
| | - Tao Xu
- Department of Pathology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Brandon R Lowe
- Department of Pathology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Yvan Pfister
- Department of Molecular Biology, Science III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 1211 Geneva 4, Switzerland
| | - Chunxu Qu
- Department of Computational Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Sreenath Shanker
- Department of Pathology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - José I Baños Sanz
- Department of Molecular Biology, Science III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 1211 Geneva 4, Switzerland
| | - Janet F Partridge
- Department of Pathology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
| | - Thomas Schalch
- Department of Molecular Biology, Science III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 1211 Geneva 4, Switzerland.
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17
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Forsburg SL, Shen KF. Centromere Stability: The Replication Connection. Genes (Basel) 2017; 8:genes8010037. [PMID: 28106789 PMCID: PMC5295031 DOI: 10.3390/genes8010037] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/10/2017] [Accepted: 01/12/2017] [Indexed: 11/16/2022] Open
Abstract
The fission yeast centromere, which is similar to metazoan centromeres, contains highly repetitive pericentromere sequences that are assembled into heterochromatin. This is required for the recruitment of cohesin and proper chromosome segregation. Surprisingly, the pericentromere replicates early in the S phase. Loss of heterochromatin causes this domain to become very sensitive to replication fork defects, leading to gross chromosome rearrangements. This review examines the interplay between components of DNA replication, heterochromatin assembly, and cohesin dynamics that ensures maintenance of genome stability and proper chromosome segregation.
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Affiliation(s)
- Susan L Forsburg
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA.
| | - Kuo-Fang Shen
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA.
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18
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Tange Y, Chikashige Y, Takahata S, Kawakami K, Higashi M, Mori C, Kojidani T, Hirano Y, Asakawa H, Murakami Y, Haraguchi T, Hiraoka Y. Inner nuclear membrane protein Lem2 augments heterochromatin formation in response to nutritional conditions. Genes Cells 2016; 21:812-32. [PMID: 27334362 DOI: 10.1111/gtc.12385] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 05/08/2016] [Indexed: 12/29/2022]
Abstract
Inner nuclear membrane proteins interact with chromosomes in the nucleus and are important for chromosome activity. Lem2 and Man1 are conserved members of the LEM-domain nuclear membrane protein family. Mutations of LEM-domain proteins are associated with laminopathy, but their cellular functions remain unclear. Here, we report that Lem2 maintains genome stability in the fission yeast Schizosaccharomyces pombe. S. pombe cells disrupted for the lem2(+) gene (lem2∆) showed slow growth and increased rate of the minichromosome loss. These phenotypes were prominent in the rich culture medium, but not in the minimum medium. Centromeric heterochromatin formation was augmented upon transfer to the rich medium in wild-type cells. This augmentation of heterochromatin formation was impaired in lem2∆ cells. Notably, lem2∆ cells occasionally exhibited spontaneous duplication of genome sequences flanked by the long-terminal repeats of retrotransposons. The resulting duplication of the lnp1(+) gene, which encodes an endoplasmic reticulum membrane protein, suppressed lem2∆ phenotypes, whereas the lem2∆ lnp1∆ double mutant showed a severe growth defect. A combination of mutations in Lem2 and Bqt4, which encodes a nuclear membrane protein that anchors telomeres to the nuclear membrane, caused synthetic lethality. These genetic interactions imply that Lem2 cooperates with the nuclear membrane protein network to regulate genome stability.
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Affiliation(s)
- Yoshie Tange
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, 565-0871, Japan.,Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe, 651-2492, Japan
| | - Yuji Chikashige
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe, 651-2492, Japan
| | - Shinya Takahata
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Kei Kawakami
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Masato Higashi
- Graduate school of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-0810, Japan
| | - Chie Mori
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe, 651-2492, Japan
| | - Tomoko Kojidani
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe, 651-2492, Japan.,Laboratory of Electron Microscopy, Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo, 112-8681, Japan
| | - Yasuhiro Hirano
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, 565-0871, Japan
| | - Haruhiko Asakawa
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, 565-0871, Japan
| | - Yota Murakami
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Tokuko Haraguchi
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, 565-0871, Japan.,Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe, 651-2492, Japan
| | - Yasushi Hiraoka
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, 565-0871, Japan.,Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe, 651-2492, Japan
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19
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Lim KK, Ong TYR, Tan YR, Yang EG, Ren B, Seah KS, Yang Z, Tan TS, Dymock BW, Chen ES. Mutation of histone H3 serine 86 disrupts GATA factor Ams2 expression and precise chromosome segregation in fission yeast. Sci Rep 2015; 5:14064. [PMID: 26369364 PMCID: PMC4570208 DOI: 10.1038/srep14064] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 08/17/2015] [Indexed: 01/08/2023] Open
Abstract
Eukaryotic genomes are packed into discrete units, referred to as nucleosomes, by organizing around scaffolding histone proteins. The interplay between these histones and the DNA can dynamically regulate the function of the chromosomal domain. Here, we interrogated the function of a pair of juxtaposing serine residues (S86 and S87) that reside within the histone fold of histone H3. We show that fission yeast cells expressing a mutant histone H3 disrupted at S86 and S87 (hht2-S86AS87A) exhibited unequal chromosome segregation, disrupted transcriptional silencing of centromeric chromatin, and reduced expression of Ams2, a GATA-factor that regulates localization of the centromere-specific histone H3 variant CENP-A. We found that overexpression of ams2+ could suppress the chromosome missegregation phenotype that arose in the hht2-S86AS87A mutant. We further demonstrate that centromeric localization of SpCENP-Acnp1-1 was significantly compromised in hht2-S86AS87A, suggesting synergism between histone H3 and the centromere-targeting domain of SpCENP-A. Taken together, our work presents evidence for an uncharacterized serine residue in fission yeast histone H3 that affects centromeric integrity via regulating the expression of the SpCENP-A-localizing Ams2 protein. [173/200 words]
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Affiliation(s)
- Kim Kiat Lim
- Department of Biochemistry, School of Medicine, National University of Singapore, Singapore.,National University Health System (NUHS), National University of Singapore, Singapore
| | - Terenze Yao Rui Ong
- Department of Biochemistry, School of Medicine, National University of Singapore, Singapore.,National University Health System (NUHS), National University of Singapore, Singapore
| | - Yue Rong Tan
- Department of Biochemistry, School of Medicine, National University of Singapore, Singapore.,National University Health System (NUHS), National University of Singapore, Singapore
| | - Eugene Guorong Yang
- Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore
| | - Bingbing Ren
- Department of Biochemistry, School of Medicine, National University of Singapore, Singapore.,National University Health System (NUHS), National University of Singapore, Singapore
| | - Kwi Shan Seah
- Department of Biochemistry, School of Medicine, National University of Singapore, Singapore.,National University Health System (NUHS), National University of Singapore, Singapore
| | - Zhe Yang
- Department of Biochemistry, School of Medicine, National University of Singapore, Singapore.,National University Health System (NUHS), National University of Singapore, Singapore
| | - Tsu Soo Tan
- School of Chemical &Life Sciences, Nanyang Polytechnic, Singapore
| | - Brian W Dymock
- Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore
| | - Ee Sin Chen
- Department of Biochemistry, School of Medicine, National University of Singapore, Singapore.,National University Health System (NUHS), National University of Singapore, Singapore.,Synthetic Biology Research Consortium, National University of Singapore, Singapore.,NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore
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20
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Eissenberg JC, Elgin SCR. HP1a: a structural chromosomal protein regulating transcription. Trends Genet 2014; 30:103-10. [PMID: 24555990 DOI: 10.1016/j.tig.2014.01.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 01/17/2014] [Accepted: 01/17/2014] [Indexed: 01/16/2023]
Abstract
Heterochromatin protein 1 (HP1a in Drosophila) is a conserved eukaryotic chromosomal protein that is prominently associated with pericentric heterochromatin and mediates the concomitant gene silencing. Mechanistic studies implicate HP1 family proteins as 'hub proteins,' able to interact with a variety of chromosomal proteins through the chromo-shadow domain (CSD), as well as to recognize key histone modification sites [primarily histone H3 di/trimethyl Lys9 (H3K9me2/3)] through the chromodomain (CD). Consequently, HP1 has many important roles in chromatin architecture and impacts both gene expression and gene silencing, utilizing a variety of mechanisms. Clearly, HP1 function is altered by context, and potentially by post-translational modifications (PTMs). Here, we report on recent ideas as to how this versatile protein accomplishes its diverse functions.
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Affiliation(s)
- Joel C Eissenberg
- Edward A. Doisy Department of Biochemistry & Molecular Biology, Saint Louis University School of Medicine, Doisy Research Center, 1100 South Grand Boulevard, St Louis, MO 63104, USA
| | - Sarah C R Elgin
- Department of Biology, Washington University in St. Louis, Campus Box 1037, One Brookings Drive, St Louis, MO 63130-4899, USA.
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21
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CRL4-like Clr4 complex in Schizosaccharomyces pombe depends on an exposed surface of Dos1 for heterochromatin silencing. Proc Natl Acad Sci U S A 2014; 111:1795-800. [PMID: 24449894 DOI: 10.1073/pnas.1313096111] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Repressive histone H3 lysine 9 methylation (H3K9me) and its recognition by HP1 proteins are necessary for pericentromeric heterochromatin formation. In Schizosaccharomyces pombe, H3K9me deposition depends on the RNAi pathway. Cryptic loci regulator 4 (Clr4), the only known H3K9 methyltransferase in this organism, is a subunit of the Clr4 methyltransferase complex (CLRC), whose composition is reminiscent of a CRL4 type cullin-RING ubiquitin ligase (CRL) including its cullin Cul4, the RING-box protein Pip1, the DNA damage binding protein 1 homolog Rik1, and the DCAF-like protein delocalization of Swi6 1 (Dos1). Dos2 and Stc1 have been proposed to be part of the complex but do not bear similarity to canonical ubiquitin ligase components. CLRC is an active E3 ligase in vitro, and this activity is necessary for heterochromatin assembly in vivo. The similarity between CLRC and the CRLs suggests that the WD repeat protein Dos1 will act to mediate target recognition and substrate specificity for CLRC. Here, we present a pairwise interaction screen that confirms a CRL4-like subunit arrangement and further identifies Dos2 as a central component of the complex and recruiter of Stc1. We determined the crystal structure of the Dos1 WD repeat domain, revealing an eight-bladed β-propeller fold. Functional mapping of the putative target-binding surface of Dos1 identifies key residues required for heterochromatic silencing, consistent with Dos1's role as the specificity factor for the E3 ubiquitin ligase.
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22
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Duffy MF, Selvarajah SA, Josling GA, Petter M. Epigenetic regulation of the Plasmodium falciparum genome. Brief Funct Genomics 2013; 13:203-16. [PMID: 24326119 DOI: 10.1093/bfgp/elt047] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recent research has highlighted some unique aspects of chromatin biology in the malaria parasite Plasmodium falciparum. During its erythrocytic lifecycle P. falciparum maintains its genome primarily as unstructured euchromatin. Indeed there is no clear role for chromatin-mediated silencing of the majority of the developmentally expressed genes in P. falciparum. However discontinuous stretches of heterochromatin are critical for variegated expression of contingency genes that mediate key pathogenic processes in malaria. These range from invasion of erythrocytes and antigenic variation to solute transport and growth adaptation in response to environmental changes. Despite lack of structure within euchromatin the nucleus maintains functional compartments that regulate expression of many genes at the nuclear periphery, particularly genes with clonally variant expression. The typical components of the chromatin regulatory machinery are present in P. falciparum; however, some of these appear to have evolved novel species-specific functions, e.g. the dynamic regulation of histone variants at virulence gene promoters. The parasite also appears to have repeatedly acquired chromatin regulatory proteins through lateral transfer from endosymbionts and from the host. P. falciparum chromatin regulators have been successfully targeted with multiple drugs in laboratory studies; hopefully their functional divergence from human counterparts will allow the development of parasite-specific inhibitors.
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23
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Woolcock KJ, Bühler M. Nuclear organisation and RNAi in fission yeast. Curr Opin Cell Biol 2013; 25:372-7. [DOI: 10.1016/j.ceb.2013.02.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 02/05/2013] [Indexed: 12/20/2022]
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24
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Li PC, Green MD, Forsburg SL. Mutations disrupting histone methylation have different effects on replication timing in S. pombe centromere. PLoS One 2013; 8:e61464. [PMID: 23658693 PMCID: PMC3641051 DOI: 10.1371/journal.pone.0061464] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 03/11/2013] [Indexed: 11/19/2022] Open
Abstract
The fission yeast pericentromere comprises repetitive sequence elements packaged into heterchromatin marked by histone H3K9 methylation and Swi6 binding. Transient disruption of Swi6 during S phase allows a period of RNA synthesis which programs the RNAi machinery to maintain histone methylation. However, Swi6 is also required for early replication timing. We show that not only Swi6 but also the chromodomain protein Chp1 are delocalized during S phase. Different from loss of swi6, mutations that disrupt histone methylation in the centromere, chp1Δ and clr4Δ, undergo early DNA replication. However, timing is modestly delayed in RNAi mutants dcr1Δ or rdp1Δ, while hrr1Δ mutants resemble swi6Δ in their replication delay. Finally, we show that recruitment of RNA polymerase II in the centromere occurs independently of replication. These different effects indicate that replication timing is not simply linked to histone methylation.
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Affiliation(s)
- Pao-Chen Li
- Molecular & Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Marc D. Green
- Molecular & Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
| | - Susan L. Forsburg
- Molecular & Computational Biology Program, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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