Genome-wide maps of CENP-A nucleosomes in three neocentromere-containing cell lines
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE44724 | GEO | 2013/05/04
SECONDARY ACCESSION(S): PRJNA191094
REPOSITORIES: GEO
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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
Project description:Epigenetic mechanisms are thought to specify the identity of centromeres, yet the degree to which DNA sequence contributes to centromere determination remains unresolved. For example, the conserved CENP-B protein binds the 17-bp âCENP-B boxâ motif found in α-satellite arrays at most human centromeres. Although CENP-B is required for artificial centromere function, it is non-essential and some species lack CENP-B boxes entirely. To address this âCENP-B paradox,â we determined the distribution of CENP-B boxes in primates and directly demonstrated the absence of CENP-B at Old World Monkey centromeres. We found extensive interspecific variation in α-satellite arrays including abundance of <10-bp dyad symmetries and of non-B-form DNA structures. We confirmed the presence of non-canonical DNA at human centromeres and neocentromeres and detected similar structures at mouse, chicken and yeast centromeres. To resolve the CENP-B paradox, we propose that CENP-B enhances non-canonical DNA formation, thus providing a general basis for centromere specification.
2018-01-28 | GSE102111 | GEO
Project description:We find that CENP-T acts as a bridge between two well-positioned CENP-A nucleosomes that are present on young alpha-satellite dimers that dominate functional human centromeres. CENP-T is centered over the CENP-B box, where it interacts with the CENP-B/CENP-C complex. Upon cross-linking, the entire CENP-A/CENP-C/CENP-T-containing complex is recovered as a nuclease-protected particle over an alpha-satellite dimer that comprises the fundamental unit of kinetochore chromatin. Our work reveals that CENP-A/CENP-C and CENP-T branches of kinetochore assembly are physically integrated.
2016-05-24 | GSE69839 | GEO
Project description:In most eukaryotes, the centromere is epigenetically defined by nucleosomes that contain the histone H3 variant centromere protein A (CENP-A). Specific targeting of the CENP-A-loading chaperone to the centromere is vital for stable centromere propagation; however, the existence of ectopic centromeres (neocentromeres) indicates that this chaperone can function in different chromatin environments. The mechanism responsible for accommodating the CENP-A chaperone at novel chromatin regions is poorly understood. Here, we report the identification of transient, immature neocentromeres in Schizosaccharomyces pombe, which show reduced association with the CENP-A chaperone Scm3 attributable to persistence of the histone H2A variant H2A.Z. Following acquisition of adjacent heterochromatin or relocation of the immature neocentromeres to subtelomeric regions, H2A.Z was depleted and Scm3 was replenished, leading to subsequent stabilization of the neocentromeres. These findings provide novel insights into histone variant-mediated epigenetic control of neocentromere establishment. Comparison of chromosomal distributions of centromeric proteins and heterochromatin proteins between the NC survivors and their derivatives.
2013-11-03 | E-GEOD-37094 | biostudies-arrayexpress
Project description:In most eukaryotes, the centromere is epigenetically defined by nucleosomes that contain the histone H3 variant centromere protein A (CENP-A). Specific targeting of the CENP-A-loading chaperone to the centromere is vital for stable centromere propagation; however, the existence of ectopic centromeres (neocentromeres) indicates that this chaperone can function in different chromatin environments. The mechanism responsible for accommodating the CENP-A chaperone at novel chromatin regions is poorly understood. Here, we report the identification of transient, immature neocentromeres in Schizosaccharomyces pombe, which show reduced association with the CENP-A chaperone Scm3 attributable to persistence of the histone H2A variant H2A.Z. Following acquisition of adjacent heterochromatin or relocation of the immature neocentromeres to subtelomeric regions, H2A.Z was depleted and Scm3 was replenished, leading to subsequent stabilization of the neocentromeres. These findings provide novel insights into histone variant-mediated epigenetic control of neocentromere establishment.
2013-11-03 | GSE37094 | GEO
Project description:Centromeres of most eukaryotes are multi-megabase arrays of satellite DNA that assemble proteinaceous kinetochores to facilitate faithful chromosome segregation. However, the nature of the chromatin landscape at centromeres remains unclear, in part due to the difficulty of isolating intact centromeric chromatin rendered insoluble by megadalton-size kinetochore protein complexes. To address this challenge we combined classical salt fractionation with chromatin immunoprecipitation to recover human centromeric chromatin under native conditions. We found that >85% of the total centromeric chromatin is insoluble under conditions typically used for native chromatin extraction. To map both soluble and insoluble chromatin in situ, we combined CUT&RUN, a targeted nuclease method, with salt fractionation. Using this approach, we found that the strength of Centromere Protein B (CENP-B) binding and the density of CENP-B motifs corresponds to the occupancy of Constitutive Centromere-Assocated Network (CCAN) complexes bound to α-satellite arrays. We also observed unexpected structural variations of CENP-A-containing complexes on different α-satellite dimeric units within highly homogenous arrays. Our results suggest that slight α-satellite sequence differences controls the structure and occupancy of the associated centromeric chromatin complex.
2018-01-31 | GSE104805 | GEO
Project description:The focal attachment of the kinetochore to the centromere core is essential for genome maintenance, yet the highly repetitive nature of human centromeres limits our understanding of their chromatin organization. We demonstrate that single-molecule chromatin fiber sequencing can uniquely resolve chromatin organization within centromeres at single-molecule and single-nucleotide resolution. We find that the centromere core contains a dichotomous chromatin organization not found elsewhere in the genome, which is characterized by highly accessible chromatin patches heterogeneously punctuated amongst tightly compacted nucleosome arrays. These highly accessible chromatin patches correspond to sites of kinetochore attachment, and clustered CENP-B occupancy within these patches phase nucleosome arrays to the alpha-satellite repeat. This dichotomous chromatin organization is conserved between humans despite the marked divergence of the underlying alpha-satellite organization and is similarly conserved in primate centromeres that lack alpha-satellite repeats, indicating that functional conservation within centromeres is mediated at the level of chromatin, not DNA.
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Project description:Centromeres, the sites of spindle attachment during mitosis and meiosis, are located in specific positions in the human genome, normally coincident with diverse subsets of alpha satellite DNA. While there is strong evidence supporting the association of some subfamilies of alpha satellite with centromere function, the basis for establishing whether a given alpha satellite sequence is or is not designated a functional centromere is unknown, and attempts to understand the role of particular sequence features in establishing centromere identity have been limited by the near identity and repetitive nature of satellite sequences. Utilizing a broadly applicable experimental approach to test sequence competency for centromere specification, we have carried out a genomic and epigenetic functional analysis of endogenous human centromere sequences available in the current human genome assembly. The data support a model in which functionally competent sequences confer an opportunity for centromere specification, integrating genomic and epigenetic signals and promoting the concept of context-dependent centromere inheritance. Sequences bound to CENP-A in HuRef cell line
2013-03-29 | E-GEOD-45497 | 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: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