A tagged histone variant exploits cancer-specific pathway in human cells
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE209933 | GEO | 2024/06/14
REPOSITORIES: GEO
Similar Datasets
Project description:CENP-A is a centromere-specific histone 3 variant essential for centromere specification. CENP-A partially replaces canonical histone H3 at the centromeres. How the particular CENP-A/H3 ratio at centromeres is precisely maintained is unknown. It also remains unclear how CENP-A is excluded from non-centromeric chromatin. Here we identify Ccp1, an uncharacterized NAP family protein in fission yeast that antagonizes CENP-A loading at both centromeric and non-centromeric regions. Like the CENP-A loading factor HJURP, Ccp1 interacts with CENP-A, and is recruited to centromeres at the end of mitosis in a Mis16-dependent manner. These data indicate that factors with opposing CENP-A loading activities are recruited to centromeres. Furthermore, Ccp1 also cooperates with H2A.Z to evict CENP-A assembled in euchromatin. Structural analyses indicate that Ccp1 forms a homodimer that is required for its anti-CENP-A loading activity. Our study establishes mechanisms for maintenance of CENP-A homeostasis at centromeres and the prevention of ectopic assembly of centromeres. Examination of cnp1 distribution in one wild type (wt) and two ccp1 mutants.
2016-08-04 | E-GEOD-85166 | biostudies-arrayexpress
Project description:CENP-A is a centromere-specific histone 3 variant essential for centromere specification. CENP-A partially replaces canonical histone H3 at the centromeres. How the particular CENP-A/H3 ratio at centromeres is precisely maintained is unknown. It also remains unclear how CENP-A is excluded from non-centromeric chromatin. Here we identify Ccp1, an uncharacterized NAP family protein in fission yeast that antagonizes CENP-A loading at both centromeric and non-centromeric regions. Like the CENP-A loading factor HJURP, Ccp1 interacts with CENP-A, and is recruited to centromeres at the end of mitosis in a Mis16-dependent manner. These data indicate that factors with opposing CENP-A loading activities are recruited to centromeres. Furthermore, Ccp1 also cooperates with H2A.Z to evict CENP-A assembled in euchromatin. Structural analyses indicate that Ccp1 forms a homodimer that is required for its anti-CENP-A loading activity. Our study establishes mechanisms for maintenance of CENP-A homeostasis at centromeres and the prevention of ectopic assembly of centromeres.
2016-08-04 | GSE85166 | GEO
Project description:At Schizosaccharomyces pombe centromeres, heterochromatin formation is required for de novo incorporation of the histone H3 variant CENP-A/Cnp1, which in turn directs kinetochore assembly and ultimately chromosome segregation during mitosis. Noncoding RNAs (ncRNAs) transcribed by RNA polymerase II (Pol II) directs heterochromatin formation via the RNAi machinery, but also through RNAiindependent RNA processing factors. Control of centromeric ncRNA transcription is therefore a key factor for proper centromere function. We here use transcriptional profiling, gene inactivation experiments, and chromatin immunoprecipitation analyses to demonstrate that the Mediator complex directs ncRNA transcription and regulates centromeric heterochromatin formation in fission yeast. Mediator co-localizes with Pol II at centromeres and loss of the Mediator subunit Med20 causes a dramatic increase in pericentromeric transcription and desilencing of the core centromere. As a consequence, heterochromatin formation is impaired both via the RNAi dependent and independent pathways, resulting in loss of CENP-A/Cnp1 from the core centromere, defect kinetochore function, and a severe chromosome segregation defect. Interestingly, the increased centromeric transcription observed in med20Δ appears to directly block CENP-A/Cnp1 incorporation and inhibition of Pol II transcription can suppress the observed phenotypes. Our data thus identify Mediator as a crucial regulator of ncRNA transcription at fission yeast centromeres and add another crucial layer of regulation to centromere function. 3 samples examined: wild type chromatin incubated with beads as the non antibody control, wild type chromatin incubated with RNA Polymerase II CTD domain antibody and Protein G beads, and TAP-Med7 cells chromatin incubated with IgG beads.
2012-11-06 | E-GEOD-35524 | biostudies-arrayexpress
Project description:Centromeres are the regions of eukaryotic chromosomes where kinetochores are assembled and direct the correct segregation of chromosomes. Active centromeres are defined by presence of nucleosomes containing CENP-A, a histone H3 variant, which alone is sufficient to direct kinetochore assembly. Once assembled at a location CENP-A chromatin and the kinetochore is maintained at that location though a positive feedback loop where kinetochore proteins recruited by CENP-A promote deposition of new CENP-A following replication. Although CENP-A chromatin itself is a heritable entity, it is normally associated with specific sequences such as human alpha satellite arrays. Such analyses suggest that properties of centromeric DNA itself may favour assembly of CENP-A rather than H3 nucleosomes. To investigate the innate properties of centromeric DNA we have examined histone dynamics on this DNA assembled in CENP-A chromatin at endogenous centromeres and when assembled only in H3 chromatin at an ectopic location. We demonstrate that H3 occupancy on centromeric DNA is innately low while H3 turnover is high. Moreover, even at an ectopic location centromeric DNA programs H3 deposition in S phase and its eviction during G2 when CENP-A is otherwise deposited. G2 accumulation of RNAPII on centromeric DNA during G2 is consistent with transcription-coupled destabilisation of H3 nucleosomes to favour CENP-A deposition.
2018-11-29 | GSE106492 | GEO
Project description:Centromeres are the regions of eukaryotic chromosomes where kinetochores are assembled and direct the correct segregation of chromosomes. Active centromeres are defined by presence of nucleosomes containing CENP-A, a histone H3 variant, which alone is sufficient to direct kinetochore assembly. Once assembled at a location CENP-A chromatin and the kinetochore is maintained at that location though a positive feedback loop where kinetochore proteins recruited by CENP-A promote deposition of new CENP-A following replication. Although CENP-A chromatin itself is a heritable entity, it is normally associated with specific sequences such as human alpha satellite arrays. Such analyses suggest that properties of centromeric DNA itself may favour assembly of CENP-A rather than H3 nucleosomes. To investigate the innate properties of centromeric DNA we have examined histone dynamics on this DNA assembled in CENP-A chromatin at endogenous centromeres and when assembled only in H3 chromatin at an ectopic location. We demonstrate that H3 occupancy on centromeric DNA is innately low while H3 turnover is high. Moreover, even at an ectopic location centromeric DNA programs H3 deposition in S phase and its eviction during G2 when CENP-A is otherwise deposited. G2 accumulation of RNAPII on centromeric DNA during G2 is consistent with transcription-coupled destabilisation of H3 nucleosomes to favour CENP-A deposition.
2018-11-29 | GSE106491 | GEO
Project description:Centromeres are the regions of eukaryotic chromosomes where kinetochores are assembled and direct the correct segregation of chromosomes. Active centromeres are defined by presence of nucleosomes containing CENP-A, a histone H3 variant, which alone is sufficient to direct kinetochore assembly. Once assembled at a location CENP-A chromatin and the kinetochore is maintained at that location though a positive feedback loop where kinetochore proteins recruited by CENP-A promote deposition of new CENP-A following replication. Although CENP-A chromatin itself is a heritable entity, it is normally associated with specific sequences such as human alpha satellite arrays. Such analyses suggest that properties of centromeric DNA itself may favour assembly of CENP-A rather than H3 nucleosomes. To investigate the innate properties of centromeric DNA we have examined histone dynamics on this DNA assembled in CENP-A chromatin at endogenous centromeres and when assembled only in H3 chromatin at an ectopic location. We demonstrate that H3 occupancy on centromeric DNA is innately low while H3 turnover is high. Moreover, even at an ectopic location centromeric DNA programs H3 deposition in S phase and its eviction during G2 when CENP-A is otherwise deposited. G2 accumulation of RNAPII on centromeric DNA during G2 is consistent with transcription-coupled destabilisation of H3 nucleosomes to favour CENP-A deposition.
2018-11-29 | GSE119922 | GEO
Project description:Centromeres are the regions of eukaryotic chromosomes where kinetochores are assembled and direct the correct segregation of chromosomes. Active centromeres are defined by presence of nucleosomes containing CENP-A, a histone H3 variant, which alone is sufficient to direct kinetochore assembly. Once assembled at a location CENP-A chromatin and the kinetochore is maintained at that location though a positive feedback loop where kinetochore proteins recruited by CENP-A promote deposition of new CENP-A following replication. Although CENP-A chromatin itself is a heritable entity, it is normally associated with specific sequences such as human alpha satellite arrays. Such analyses suggest that properties of centromeric DNA itself may favour assembly of CENP-A rather than H3 nucleosomes. To investigate the innate properties of centromeric DNA we have examined histone dynamics on this DNA assembled in CENP-A chromatin at endogenous centromeres and when assembled only in H3 chromatin at an ectopic location. We demonstrate that H3 occupancy on centromeric DNA is innately low while H3 turnover is high. Moreover, even at an ectopic location centromeric DNA programs H3 deposition in S phase and its eviction during G2 when CENP-A is otherwise deposited. G2 accumulation of RNAPII on centromeric DNA during G2 is consistent with transcription-coupled destabilisation of H3 nucleosomes to favour CENP-A deposition.
2019-03-04 | GSE112454 | GEO
Project description:The histone H3 variant, CENP-ACnp1, is normally assembled upon canonical centromeric sequences, but there is no apparent obligate coupling of sequence and assembly, suggesting that centromere location can be epigenetically determined. To explore the tolerances and constraints on CENP-ACnp1 deposition we investigated whether certain locations are favoured when additional CENP-ACnp1 is present in fission yeast cells. Our analyses show that additional CENP-ACnp1 accumulates within and close to heterochromatic centromeric outer repeats, and over regions adjacent to rDNA and telomeres. The use of minichromosome derivatives with unique DNA sequences internal to chromosome ends shows that telomeres are sufficient to direct CENP-ACnp1 deposition. However, chromosome ends are not required as CENP-ACnp1 deposition also occurs at telomere repeats inserted at an internal locus and correlates with the presence of H3K9 methylation near these repeats. The Ccq1 protein, which is known to bind telomere repeats and recruit telomerase, was found to be required to induce H3K9 methylation and thus promote the incorporation of CENP-A near telomere repeats. These analyses demonstrate that at non-centromeric chromosomal locations the presence of heterochromatin influences the sites at which CENP-A is incorporated into chromatin and thus, potentially the location of centromeres. For CENP-A/Cnp1 chromatin immunoprecipitation: DNA immunoprecipitated with anti-Cnp1 serum using chromatin extracts from mutants and wild type control cells in biological duplicates normalized to input DNA from each strain.
2013-08-22 | E-GEOD-46427 | biostudies-arrayexpress
Project description:The centromeric histone H3 variant CENP-A is overexpressed in many cancers. Mislocalization of CENP-A to non-centromeric regions contributes to chromosomal instability (CIN), a hallmark of cancer. Despite these observations, pathways that promote and prevent CENP-A mislocalization remain poorly defined. Here, we performed a genome-wide RNAi screen to identify regulators of CENP-A localization. We identified DNAJC9, a J-domain protein as a lead candidate from the screen and showed that cells depleted for DNAJC9 exhibit mislocalization of CENP-A, enrichment of CENP-A in chromatin, and CIN phenotypes. Global interactome analysis showed an enhanced interaction of CENP-A with the replication-associated H3-H4 chaperone MCM2 in DNAJC9-depleted cells and co-depletion of MCM2 and DNAJC9 suppressed CENP-A mislocalization. Furthermore, we showed that cells ablated for the ability of DNAJC9 to promote the proper folding of H3–H4, exhibit CENP-A mislocalization. CUT&RUN Sequencing analysis of genome-wide CENP-A occupancy in DNAJC9-depleted cells identified 16,603 sites of non-centromeric localization, that broadly overlapped with open chromatin regions. Our comprehensive analysis has identified factors that prevent mislocalization of CENP-A and has defined DNAJC9 as an important safeguard that prevents CENP-A mislocalization and CIN.
2024-03-26 | GSE253387 | GEO
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. In total, 24 samples: 22 ChIP DNA files (10 different conditions), 2 Input files.
2015-02-19 | E-GEOD-66106 | biostudies-arrayexpress