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Human centromere repositioning activates transcription and opens chromatin fibre structure [Agilent bTMP-chip]

ABSTRACT: This study was designed to investigate the chromatin structure of human centromeres. Human centromeres appear as constrictions on mitotic chromosomes and form a platform for kinetochore assembly in mitosis. Biophysical experiments led to a suggestion that repetitive DNA at centromeric regions form a compact scaffold necessary for function, but this was revised when neocentromeres were discovered on non-repetitive DNA. To test whether centromeres have a special chromatin structure we have analysed the architecture of a neocentromere. Centromere formation is accompanied by RNA pol II recruitment and active transcription to form a decompacted, negatively supercoiled domain enriched in ‘open’ chromatin fibres. In contrast, centromerisation causes a spreading of repressive epigenetic marks to surrounding regions, delimited by H3K27me3 polycomb boundaries and divergent genes. This flanking domain is transcriptionally silent and partially remodelled to form ‘compact’ chromatin, similar to satellite-containing DNA sequences, and exhibits genomic instability. We suggest transcription disrupts chromatin to provide a foundation for kinetochore formation whilst compact pericentromeric heterochromatin generates mechanical rigidity.

ORGANISM(S): Homo sapiens Cricetulus griseus

PROVIDER: GSE195884 | GEO | 2022/09/07

REPOSITORIES: GEO

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Human centromere repositioning activates transcription and opens chromatin fibre structure [Agilent 'open' chromatin-chip]

Project description:This study was designed to investigate the chromatin structure of human centromeres. Human centromeres appear as constrictions on mitotic chromosomes and form a platform for kinetochore assembly in mitosis. Biophysical experiments led to a suggestion that repetitive DNA at centromeric regions form a compact scaffold necessary for function, but this was revised when neocentromeres were discovered on non-repetitive DNA. To test whether centromeres have a special chromatin structure we have analysed the architecture of a neocentromere. Centromere formation is accompanied by RNA pol II recruitment and active transcription to form a decompacted, negatively supercoiled domain enriched in ‘open’ chromatin fibres. In contrast, centromerisation causes a spreading of repressive epigenetic marks to surrounding regions, delimited by H3K27me3 polycomb boundaries and divergent genes. This flanking domain is transcriptionally silent and partially remodelled to form ‘compact’ chromatin, similar to satellite-containing DNA sequences, and exhibits genomic instability. We suggest transcription disrupts chromatin to provide a foundation for kinetochore formation whilst compact pericentromeric heterochromatin generates mechanical rigidity.

2022-09-07 | GSE195883 | GEO

Human centromere repositioning activates transcription and opens chromatin fibre structure [Agilent ChIP-chip]

2022-09-07 | GSE195885 | GEO

Human centromere repositioning activates transcription and opens chromatin fibre structure [RNAseq]

Project description:Human centromeres appear as constrictions on mitotic chromosomes and form a platform for kinetochore assembly in mitosis. Biophysical experiments led to a suggestion that repetitive DNA at centromeric regions form a compact scaffold necessary for function, but this was revised when neocentromeres were discovered on non-repetitive DNA. To test whether centromeres have a special chromatin structure we have analysed the architecture of a neocentromere. Centromere formation is accompanied by RNA pol II recruitment and active transcription to form a decompacted, negatively supercoiled domain enriched in ‘open’ chromatin fibres. In contrast, centromerisation causes a spreading of repressive epigenetic marks to surrounding regions, delimited by H3K27me3 polycomb boundaries and divergent genes. This flanking domain is transcriptionally silent and partially remodelled to form ‘compact’ chromatin, similar to satellite-containing DNA sequences, and exhibits genomic instability. We suggest transcription disrupts chromatin to provide a foundation for kinetochore formation whilst compact pericentromeric heterochromatin generates mechanical rigidity.

2022-09-07 | GSE196160 | GEO

Human centromere repositioning activates transcription and opens chromatin fibre structure [TTseq]

2022-09-07 | GSE196155 | GEO

Genome-wide maps of CENP-A nucleosomes in three neocentromere-containing cell lines

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

Genome-wide maps of CENP-A nucleosomes in three neocentromere-containing cell lines

2013-05-04 | GSE44724 | GEO

Conservation of chromatin organization within human and primate centromeres

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.

2023-08-02 | GSE226394 | GEO

Centromere-Like Regions in Budding Yeast

Project description:Accurate chromosome segregation requires centromeres (CENs), the chromosomal sites where kinetochores form, to bridge DNA and attach to microtubules. In contrast to most eukaryotes, Saccharomyces cerevisiae possesses sequence-defined point centromeres. Chromatin immunoprecipitation followed by sequencing (ChIP-Seq) of four kinetochore components reveals regions of overlapping, extra-centromeric protein localization upon overproduction of the centromeric histone, Cse4 (CENP-A or CenH3). These identified sequences enhance proper plasmid and chromosome segregation, and are termed Centromere-like Regions (CLRs). CLRs form in close proximity to S. cerevisiae CENs and share characteristics typical of point and regional centromeres. CLR sequences are conserved among related budding yeasts, suggesting a role in vivo. These studies provide new insights into the origin and evolution of centromeres. ChIP-Seq analysis of the kinetochore components Cse4, Mif2, Ndc10 and Ndc80 in budding yeast strains (Saccharomyces cerevisiae) with normal and elevated levels of Cse4

2013-01-18 | E-GEOD-31466 | biostudies-arrayexpress

Epigenetically induced paucity of histone H2A.Z stabilizes fission yeast ectopic centromeres

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

Single-molecule chromatin architectures of human centromeres and telomeres

Project description:Centromeres and telomeres are essential structural components of eukaryotic genomes, and alterations in their structure and function contribute to various human diseases. Currently, our understanding of the chromatin architecture underlying centromeres and telomeres is limited owing to their highly repetitive DNA content. To overcome this, we applied long-read single-molecule chromatin fiber-sequencing (Fiber-seq) to a human cell line with a complete telomere-to-telomere (T2T) reference genome, resulting in single-nucleotide precise mapping of chromatin accessibility, nucleosome positioning, and transcription factor occupancy across 1.7 million intact ~16kb chromatin fibers - resolving the chromatin architecture for ~97% of human telomeric and centromeric DNA. We identify that the centromeric kinetochore binding region contains highly atypical chromatin that juxtaposes highly accessible and tightly compacted DNA - a feature unique to the kinetochore. This structure mirrors the alpha-satellite DNA repeat and appears driven via clustered CENP-B occupancy at hypo-CpG methylated repeats. In addition, telomeres often contain several kilobases of non-nucleosomal chromatin, and the transition between nucleosome-bound chromatin and the telomere cap is highly heterogeneous and often punctuated by CTCF-bound elements. Our findings uncover non-standard chromatin architectures as the predominant organizational structure of telomeres and the kinetochore binding region, and provide a framework for future studies of complete human epigenomes.

2022-05-10 | GSE186009 | GEO

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