Centromeric DNA destabilizes H3 nucleosomes to promote CENP-A deposition during the cell cycle (part 1)
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PROVIDER: PRJNA417133 | ENA |
REPOSITORIES: ENA
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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:Centromeric DNA destabilizes H3 nucleosomes to promote CENP-A deposition during the cell cycle (part 2)
| PRJNA417132 | ENA
Project description:Centromeric DNA destabilizes H3 nucleosomes to promote CENP-A deposition during the cell cycle (part 3)
| PRJNA490713 | ENA
Project description:Centromeric DNA destabilizes H3 nucleosomes to promote CENP-A deposition during the cell cycle
| PRJNA417043 | ENA
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: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.
2013-03-14 | GSE44206 | 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
Project description:We used native ChIP-seq of CENP-A-containing particles from normal centromeres on alpha-satellite DNA and three naturally-occurring neocentromeres to test the proposed models for the major form of the fundamental repeating unit of centromeric chromatin. We found that the predominant form of the CENP-A particle at the centromere is an octameric nucleosome with loose terminal DNA. Additionally, we found CENP-A nucleosomes are strongly phased on the 171 bp alpha-satellite monomers of normal centromeres, and also display strong positioning and neocentromeres. Comparison of CENP-A and bulk nucleosome DNA lengths and positions in three different human neocentromere-containing cell lines
2013-05-04 | E-GEOD-44724 | biostudies-arrayexpress