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.
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.
Project description:We report the high-throughput profiling of histone variant CNEP-A/Cnp1 in fission yeast Schizosaccharomyces pombe. By obtaining 1-10 ng immunoprecipitated DNA, we generated genome-wide CENP-A/Cnp1 maps of the wild type meiotic haploid progeny of heterozygous deletion diploid wip1∆/+, mhf1∆/+ and mhf2∆/+ and CENP-A/Cnp1 maps of mhf2+ carrying the inactivated Centromere 1 or Centromere 2. We find that CENP-A/Cnp1 spreading into the pericentromeric regions in wild type meiotic progeny of heterozygous deletion diploid wip1∆/+, mhf1∆/+ and mhf2∆/+.
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
Project description:We report the high-throughput profiling of histone modification (H3K9me2) or histone variant CNEP-A/Cnp1 in fission yeast Schizosaccharomyces pombe. By obtaining 1-10 ng immunoprecipitated DNA, we generated genome-wide H3K9me2 or CENP-A/Cnp1 maps of both mhf2∆ and mhf2+ carrying the inactivated Centromere 1 or Centromere 2 in fission yeast. We find that neocemtromeres are formed preferably at pericentromeric regions in single depletion of CENP-T-W-X-S.
Project description:We report the high-throughput profiling of histone variant CNEP-A/Cnp1 in fission yeast Schizosaccharomyces pombe. By obtaining 1-10 ng immunoprecipitated DNA, we generated genome-wide CENP-A/Cnp1 maps of the meiotic progeny from the genetic crossing of mhf2∆ (cen1_inactive) × clr4∆ (cen1_active) in fission yeast. We find that heterochromatin is not required for the induction of centromere inactivation.
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.
Project description:We report the high-throughput profiling of histone modification (H3K9me2) or histone variant CNEP-A/Cnp1 in fission yeast Schizosaccharomyces pombe. By obtaining 1-10 ng immunoprecipitated DNA, we generated genome-wide H3K9me2 or CENP-A/Cnp1 maps of wild type strains carrying the inactivated Centromere 1 or Centromere 2 or Cnp1 spreading in fission yeast with a reporter gene ura4 cassette inserted into the right side of the repetitive sequences of Chromosome 1 . We find that neocemtromeres are formed preferably at pericentromeric regions ubiquitously and asymmetrically in all three centromeres of these indicated strains.
Project description:We report the high-throughput profiling of histone modification (H3K9me2) or histone variant CNEP-A/Cnp1 in fission yeast Schizosaccharomyces pombe. By obtaining 1-10 ng immunoprecipitated DNA, we generated genome-wide H3K9me2 or CENP-A/Cnp1 maps of heterozygous deletion diploid mhf2∆/+ and the meiotic haploid progeny of heterozygous deletion diploid wip1∆/+, mhf1∆/+ and mhf2∆/+ in fission yeast. We find that centromere inactivation and neocentromere formation occur independently and postzygotically in single depletion of CENP-T-W-X-S.
