Histone H3-G34V and H3-G34R mutant fission yeast exhibit distinct chromatin changes and different DNA damage sensitivities.
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ABSTRACT:
PROVIDER: PRJNA418713 | ENA |
REPOSITORIES: ENA
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Project description:Recurrent somatic mutations of H3F3A in aggressive pediatric high-grade gliomas generate K27M or G34R mutant histone H3.3. H3.3-G34R mutants are common in tumors additionally mutant for p53 and ATRX, an H3.3-specific chromatin remodeler. To gain insight into the role of H3-G34R, we generated fission yeast that express only the mutant histone H3. H3-G34R specifically reduces H3K36 tri-methylation and H3K36 acetylation, but minimally affects transcriptional control. H3-G34R mutants exhibit genomic instability and increased replicative stress including slowed replication fork restart although DNA replication checkpoints are functional. H3-G34R mutants are defective for DNA damage repair by homologous recombination (HR), and on damage have altered HR protein dynamics suggestive that H3-G34R slows resolution of HR-mediated repair. In summary our analysis of H3-G34R mutant fission yeast provides mechanistic insight into how G34R mutation may promote genomic instability in glioma.
2018-11-15 | GSE106979 | GEO
Project description:Recurrent somatic mutations of H3F3A in aggressive pediatric high-grade gliomas generate K27M or G34R mutant histone H3.3. H3.3-G34R mutants are common in tumors additionally mutant for p53 and ATRX, an H3.3-specific chromatin remodeler. To gain insight into the role of H3-G34R, we generated fission yeast that express only the mutant histone H3. H3-G34R specifically reduces H3K36 tri-methylation and H3K36 acetylation, but minimally affects transcriptional control. H3-G34R mutants exhibit genomic instability and increased replicative stress including slowed replication fork restart although DNA replication checkpoints are functional. H3-G34R mutants are defective for DNA damage repair by homologous recombination (HR), and on damage have altered HR protein dynamics suggestive that H3-G34R slows resolution of HR-mediated repair. In summary our analysis of H3-G34R mutant fission yeast provides mechanistic insight into how G34R mutation may promote genomic instability in glioma.
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Project description:Deep sequencing of cancer genomes has identified frequent mutation of core histones, termed oncohistones, but the role of some mutants is poorly understood. Here, using fission yeast as a model, we determine the consequences of mutation of histone H3.3 at Gly 34, a site frequently mutated in pediatric cortical high-grade glioma (G34R/V), and in virtually all giant cell tumors of bone (G34W). H3-G34 mutations cause a surprising diversity of outcomes, differentially affecting modification of the nearby H3K36 residue, subtelomeric silencing, genomic stability, sensitivity to irradiation, alkylating agents, hydroxyurea and influencing DNA repair. Since fifteen genes encode H3 isoforms, and only one allele is targeted in cancer, G34R/V/W H3 likely represents a small portion of total cellular H3. Whilst the presence of wild type H3 rescues most G34 mutant phenotypes, hydroxyurea sensitivity, subtelomeric silencing and homologous recombination defects dominate in cells expressing G34R and wild type H3. Together, these studies demonstrate the complexity associated with different substitutions at even a single residue in histone H3 and highlight the utility of genetically tractable systems for their analysis.
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Project description:Sequencing of paediatric gliomas has identified two common substitution mutations (K27M and G34R) in genes encoding histone H3.3. We introduced a single-copy H3.3 G34R targeted mutation in mouse ES cells and observed gains in H3K36me3 and H3K9me3 across the genome. Altered chromatin profiles correlated with enrichment of KDM4 A/B/C, a histone lysine (K9/K36) demethylase. RNA-seq of H3.3 G34R mutant showed disrupted gene expression patterns which also correlated with KDM4 enrichment. Expression of a single copy of H3.3 G34R at endogenous levels was sufficient to genocopy KDM4 triple-KO cells as determined by ChIP-seq and RNA-seq.
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Project description:Specialized chromatin containing CENP-A nucleosomes instead of H3 nucleosomes is found at all centromeres. However, the mechanisms that specify the locations at which CENP-A chromatin is assembled remain elusive in organisms with regional, epigenetically regulated centromeres. It is known that normal centromeric DNA is transcribed in several systems including the fission yeast, Schizosaccharomyces pombe. Here, we show that factors which preserve stable histone H3 chromatin during transcription also play a role in preventing promiscuous CENP-A(Cnp1) deposition in fission yeast. Mutations in the histone chaperone FACT impair the maintenance of H3 chromatin on transcribed regions and promote widespread CENP-A(Cnp1) incorporation at non-centromeric sites. FACT has little or no effect on CENP-A(Cnp1) assembly at endogenous centromeres where CENP-A(Cnp1) is normally assembled. In contrast, Clr6 complex II (Clr6-CII; equivalent to Rpd3S) histone deacetylase function has a more subtle impact on the stability of transcribed H3 chromatin and acts to prevent the ectopic accumulation of CENP-A(Cnp1) at specific loci, including subtelomeric regions, where CENP-A(Cnp1) is preferentially assembled. Moreover, defective Clr6-CII function allows the de novo assembly of CENP-A(Cnp1) chromatin on centromeric DNA, bypassing the normal requirement for heterochromatin. Thus, our analyses show that alterations in the process of chromatin assembly during transcription can destabilize H3 nucleosomes and thereby allow CENP-A(Cnp1) to assemble in its place. We propose that normal centromeres provide a specific chromatin context that limits reassembly of H3 chromatin during transcription and thereby promotes the establishment of CENP-A(Cnp1) chromatin and associated kinetochores. These findings have important implications for genetic and epigenetic processes involved in centromere specification.
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