Ccp1 homodimer mediates chromatin integrity by antagonizing CENP-A loading
Ontology highlight
ABSTRACT:
ORGANISM(S): Schizosaccharomyces pombe
SUBMITTER: Fei Li
PROVIDER: E-GEOD-85166 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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.
2016-08-04 | GSE85166 | GEO
Project description:We employ the well-studied fission yeast centromere to investigate the function of the CENP-A (Cnp1) N-tail. We show that alteration of the N-tail did not affect Cnp1 loading at centromeres, outer kinetochore formation, or spindle checkpoint signaling, but nevertheless elevated chromosome loss. N-Tail mutants exhibited synthetic lethality with an altered centromeric DNA sequence, with rare survivors harboring chromosomal fusions in which the altered centromere was epigenetically inactivated. Elevated centromere inactivation was also observed for N-tail mutants with unaltered centromeric DNA sequences. N-tail mutants specifically reduced localization of the CCAN proteins Cnp20/CENP-T and Mis6/CENP-I, but not Cnp3/CENP-C. Overexpression of Cnp20/CENP-T suppressed defects in an N-tail mutant, suggesting a causal link between reduced CENP-T recruitment and the observed centromere inactivation phenotype. Thus, the Cnp1 N-tail promotes epigenetic stability of centromeres via recruitment of the CENP-T branch of the CCAN. Genome-wide localization of GFP-tagged N-tail Cnp1 variant tailswap versus wt control in cnp1 deletion background
2015-04-16 | E-GEOD-63350 | biostudies-arrayexpress
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
Project description:We employ the well-studied fission yeast centromere to investigate the function of the CENP-A (Cnp1) N-tail. We show that alteration of the N-tail did not affect Cnp1 loading at centromeres, outer kinetochore formation, or spindle checkpoint signaling, but nevertheless elevated chromosome loss. N-Tail mutants exhibited synthetic lethality with an altered centromeric DNA sequence, with rare survivors harboring chromosomal fusions in which the altered centromere was epigenetically inactivated. Elevated centromere inactivation was also observed for N-tail mutants with unaltered centromeric DNA sequences. N-tail mutants specifically reduced localization of the CCAN proteins Cnp20/CENP-T and Mis6/CENP-I, but not Cnp3/CENP-C. Overexpression of Cnp20/CENP-T suppressed defects in an N-tail mutant, suggesting a causal link between reduced CENP-T recruitment and the observed centromere inactivation phenotype. Thus, the Cnp1 N-tail promotes epigenetic stability of centromeres via recruitment of the CENP-T branch of the CCAN.
2015-04-16 | GSE63350 | 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.
2015-02-19 | GSE66106 | 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.
2012-11-06 | GSE35524 | 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 specialized chromatin regions marked by the presence of nucleosomes containing the centromere-specific histone H3 variant CENP-A, which is essential for chromosome segregation. Assembly and disassembly of nucleosomes is intimately linked to DNA topology and DNA topoisomerases have previously been implicated in the dynamics of canonical H3 nucleosomes. Here we show that Schizosaccharomyces pombe Top3 and its partner Rqh1 are involved in controlling the levels of CENP-ACnp1 at centromeres. Both top3 and rqh1 mutants display defects in chromosome segregation. Using chromatin immunoprecipitation and tiling microarrays we show that Top3 unlike Top1 and Top2 is highly enriched at centromeric central domains, demonstrating that Top3 is the major topoisomerase in this region. Moreover, centromeric Top3 occupancy positively correlates with CENP-ACnp1 occupancy. Intriguingly, both top3 and rqh1 mutants display increased relative enrichment of CENP-ACnp1 at centromeric central domains. Thus, Top3 and Rqh1 normally limit the levels of CENP-ACnp1 in this region. This new role is independent of the established function of Top3 and Rqh1 in homologous recombination downstream of Rad51. Therefore, we hypothesize that the Top3-Rqh1 complex has an important role in controlling centromere DNA topology which in turn affects the dynamics of CENP-ACnp1 nucleosomes. For transcription: Total RNA from top3-105 mutant and WT control cells after 8 hours at 36C in biological duplicates. For Top3-myc chromatin immunoprecipitation: DNA immunoprecipitated with mouse anti-Myc using chromatin extracts from cells expressing Top3-Myc from the endogenous locus at 30C in biological duplicates normalized to input DNA from wild type cells at 30C in biological duplicates. For CENP-A/Cnp1 chromatin immunoprecipitation: DNA immunoprecipitated with anti-Cnp1 serum using chromatin extracts from top3-105 mutant and wild type control cells after 8 hours at 36C in in biological duplicates normalized to input DNA from each strain.
2013-03-14 | E-GEOD-44206 | biostudies-arrayexpress
Project description:We use high-resolution chemical cleavage mapping and both native and cross-linked chromatin immunoprecipitation with paired-end sequencing to elucidate the profile of nuceleosomes containing the centromere-specific variant of H3 (cenH3), known as CENP-A or Cnp1 in fission yeast. We find that in the central domain of fission yeast centromeres H3 nucleosomes are nearly absent and CENP-A nucleosomes are more widely spaced that nucleosomes elsewere. CENP-A (Cnp1), CENP-C (Cnp3), CENP-T (Cnp20) and CENP-I (Mis6) are highly enriched at every position in the central domain except at tRNA genes, with weak enrichment in the flanking heterochromatin where these proteins show no evidence of the positioning that has been seen in point centromeres and in the satellite-rich centromeres of plants and animals. Our findings suggest that classical regional centromeres are distinguished from other centromere classes by the absence of cenH3 nucleosome positioning.
2015-08-17 | GSE64294 | GEO
Project description:Centromere is the chromosomal locus at which kinetochore is assembled to direct chromosome segregation. Histone H3 variant CENP-A epigenetically marks active centromeres; however, the mechanism by which CENP-A propagates at the centromere, replacing histone H3, remains poorly understood. Using fission yeast, we find that CENP-ACnp1 chromatin assembly at the centromere requires the Ino80 ATP-dependent chromatin remodeling complex which removes histone H3-containing nucleosomes from associated chromatin. CENP-ACnp1 chromatin actively recruits the Ino80 complex to centromeres to elicit eviction of histone H3-containing nucleosomes. Artificial targeting of Ino80 subunits to a non-centromeric DNA placed in a native centromere enhances the spreading of CENP-ACnp1 chromatin into the non-centromeric DNA. Based on these results, we propose that CENP-ACnp1 chromatin employs the Ino80 complex to mediate replacement of histone H3 with CENP-ACnp1, and thereby reinforces itself.
2017-07-14 | GSE99589 | GEO