A transcriptional roadblock protects yeast centromeres
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ABSTRACT:
PROVIDER: PRJNA781283 | ENA |
REPOSITORIES: ENA
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Project description:Centromeres are the chromosomal loci essential for faithful chromosome segregation during cell division. Although centromeres are transcribed and produce non-coding RNAs (cenRNAs) that affect centromere function, we still lack a mechanistic understanding of how centromere transcription is regulated. Here, using a targeted RNA isoform sequencing approach, we identified the transcriptional landscape at and surrounding all centromeres in budding yeast. Overall, cenRNAs are derived from transcription readthrough of pericentromeric regions but rarely span the entire centromere and are a complex mixture of molecules that are heterogeneous in abundance, orientation, and sequence. While most pericentromeres are transcribed throughout the cell cycle, centromere accessibility to the transcription machinery is restricted to S-phase. This temporal restriction is dependent on Cbf1, a centromere-binding transcription factor, that we demonstrate acts locally as a transcriptional roadblock. Cbf1 deletion leads to an accumulation of cenRNAs at all phases of the cell cycle which correlates with increased chromosome mis-segregation that is partially rescued when the roadblock activity is restored. We propose that a Cbf1-mediated transcriptional roadblock protects yeast centromeres from untimely transcription to ensure genomic stability.
2022-02-07 | GSE189063 | GEO
Project description:This SuperSeries is composed of the following subset Series: GSE32310: Transcriptome analysis of mediator Med20 mutant and dcr1 mutant in S.pombe GSE35524: Mediator promotes CENP-A incorporation at fission yeast centromeres [ChIP-seq] Refer to individual Series
2012-11-06 | E-GEOD-35527 | 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: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: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:Pneumocystis is a relevant genetic system to study centromere formation in relation with host adaptation. How centromeres are formed and maintained in strongly host adapted fungal pathogens is poorly investigated. Centromeres are genomic regions that coordinate accurate chromosomal segregation during mitosis and meiosis. Yet, despite their essential function, centromeres evolve rapidly across eukaryotes. CENP-A, a variant of histone H3 is the epigenetic marker that define centromeres in most eukaryotes. Centromeres are often the sites of chromosomal breaks which contribute to genome shuffling and promote speciation by inhibiting gene flow. Genome shuffling allows genome reconfiguration suitable for survival in new environment such as pathogen adaptation to new hosts. Here, we study the evolution of centromeres in closely related species of mammalian specific pathogens of the fungal phylum of Ascomycota. Long term culture of Pneumocystis species is currently untenable. Using heterologous complementation, we show that Pneumocystis CENP-A ortholog is functionally equivalent to fission yeast Cnp1. Using a short-term in vitro culture, infected animal models and ChIP-seq, we identified centromeres in three Pneumocystis species that diverged ~100 Mya ago. Each species has 17 unique short regional centromeres (< 10kb) in 17 monocentric chromosomes. The centromeres are flanked by heterochromatin. They span active genes, lack conserved DNA sequence motifs, and repeats.These features suggest an epigenetic specification of centromere function.
2023-09-11 | GSE226536 | GEO
Project description:A defining feature of centromeres is the presence of the histone H3 variant CENP-ACnp1. It is not known how CENP-ACnp1 is specifically delivered to, and assembled into centromeric chromatin. Through a screen for factors involved in kinetochore integrity in fission yeast we identified Sim3. Sim3 is homologous to known histone binding proteins NASPHuman and N1/N2Xenopus and aligns with Hif1S.cerevisiae to define the SHNi-TPR family. Sim3 associates with CENP-ACnp1 but is distributed throughout the nucleoplasm rather than being concentrated at centromeres. Cells defective in Sim3 function have reduced levels of CENP-ACnp1 at centromeres and display chromosome segregation defects. Newly synthesized CENPACnp1 can be deposited at centromeres by a replication-independent mechanism during G2. Sim3 is required to allow this new CENP-ACnp1 to accumulate at centromeres in S and G2-phase arrested cells. We propose that Sim3 acts as an escort which hands off CENP-ACnp1 to chromatin assembly factors, allowing its incorporation into centromeric chromatin. Keywords: Expression of sim3-143 versus wt and sim3-205 versus wt
2007-11-10 | GSE7560 | GEO
Project description:Pneumocystis is a relevant genetic system to study centromere formation in relation with host adaptation. How centromeres are formed and maintained in strongly host adapted fungal pathogens is poorly investigated. Centromeres are genomic regions that coordinate accurate chromosomal segregation during mitosis and meiosis. Yet, despite their essential function, centromeres evolve rapidly across eukaryotes. CENP-A, a variant of histone H3 is the epigenetic marker that define centromeres in most eukaryotes. Centromeres are often the sites of chromosomal breaks which contribute to genome shuffling and promote speciation by inhibiting gene flow. Genome shuffling allows genome reconfiguration suitable for survival in new environment such as pathogen adaptation to new hosts. Here, we study the evolution of centromeres in closely related species of mammalian specific pathogens of the fungal phylum of Ascomycota. Long term culture of Pneumocystis species is currently untenable. Using heterologous complementation, we show that Pneumocystis CENP-A ortholog is functionally equivalent to fission yeast Cnp1. Using a short-term in vitro culture, infected animal models and ChIP-seq, we identified centromeres in three Pneumocystis species that diverged ~100 Mya ago. Each species has 17 unique short regional centromeres (< 10kb) in 17 monocentric chromosomes. The centromeres are flanked by heterochromatin. They span active genes, lack conserved DNA sequence motifs, and repeats.These features suggest an epigenetic specification of centromere function.
2024-02-08 | GSE232454 | GEO
Project description:Pneumocystis is a relevant genetic system to study centromere formation in relation with host adaptation. How centromeres are formed and maintained in strongly host adapted fungal pathogens is poorly investigated. Centromeres are genomic regions that coordinate accurate chromosomal segregation during mitosis and meiosis. Yet, despite their essential function, centromeres evolve rapidly across eukaryotes. CENP-A, a variant of histone H3 is the epigenetic marker that define centromeres in most eukaryotes. Centromeres are often the sites of chromosomal breaks which contribute to genome shuffling and promote speciation by inhibiting gene flow. Genome shuffling allows genome reconfiguration suitable for survival in new environment such as pathogen adaptation to new hosts. Here, we study the evolution of centromeres in closely related species of mammalian specific pathogens of the fungal phylum of Ascomycota. Long term culture of Pneumocystis species is currently untenable. Using heterologous complementation, we show that Pneumocystis CENP-A ortholog is functionally equivalent to fission yeast Cnp1. Using a short-term in vitro culture, infected animal models and ChIP-seq, we identified centromeres in three Pneumocystis species that diverged ~100 Mya ago. Each species has 17 unique short regional centromeres (< 10kb) in 17 monocentric chromosomes. The centromeres are flanked by heterochromatin. They span active genes, lack conserved DNA sequence motifs, and repeats.These features suggest an epigenetic specification of centromere function.
2024-02-08 | GSE232453 | GEO
Project description:Pneumocystis is a relevant genetic system to study centromere formation in relation with host adaptation. How centromeres are formed and maintained in strongly host adapted fungal pathogens is poorly investigated. Centromeres are genomic regions that coordinate accurate chromosomal segregation during mitosis and meiosis. Yet, despite their essential function, centromeres evolve rapidly across eukaryotes. CENP-A, a variant of histone H3 is the epigenetic marker that define centromeres in most eukaryotes. Centromeres are often the sites of chromosomal breaks which contribute to genome shuffling and promote speciation by inhibiting gene flow. Genome shuffling allows genome reconfiguration suitable for survival in new environment such as pathogen adaptation to new hosts. Here, we study the evolution of centromeres in closely related species of mammalian specific pathogens of the fungal phylum of Ascomycota. Long term culture of Pneumocystis species is currently untenable. Using heterologous complementation, we show that Pneumocystis CENP-A ortholog is functionally equivalent to fission yeast Cnp1. Using a short-term in vitro culture, infected animal models and ChIP-seq, we identified centromeres in three Pneumocystis species that diverged ~100 Mya ago. Each species has 17 unique short regional centromeres (< 10kb) in 17 monocentric chromosomes. The centromeres are flanked by heterochromatin. They span active genes, lack conserved DNA sequence motifs, and repeats.These features suggest an epigenetic specification of centromere function.
2024-02-08 | GSE232357 | GEO