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Global Regulation of Nucleosome Organization And Transcription By The Yeast Ssn6-Tup1 Corepressor (MNase-Seq)

ABSTRACT: The yeast Ssn6-Tup1 complex regulates gene expression through a variety of mechanisms, including positioning of nucleosomes over promoters of some target genes to limit accessibility to the transcription machinery. To further define the functions of Ssn6-Tup1 in gene regulation and chromatin remodeling, we performed genome-wide profiling of changes in nucleosome organization and gene expression that occur upon loss of SSN6 or TUP1, and observed extensive nucleosome alterations in both promoters and gene bodies of derepressed genes. Our improved nucleosome profiling and analysis approaches revealed low-occupancy promoter nucleosomes (P nucleosomes) at locations previously defined as nucleosome-free regions. In the absence of SSN6 or TUP1, this P nucleosome is frequently lost, whereas nucleosomes are gained at -1 and +1 positions, accompanying up-regulation of downstream genes. Our analysis of public ChIP-seq data revealed that Ssn6 and Tup1 preferentially bind TATA-containing promoters, which are also enriched in genes derepressed upon loss of SSN6 or TUP1. These results suggest that stabilization of the P nucleosome on TATA-containing promoters may be a central feature of the repressive chromatin architecture created by the Ssn6-Tup1 corepressor, and that releasing the P nucleosome contributes to gene activation. nucleosomes were prepared from isogenic wild type (BY4742), ssn6 KO and tup1 KO cells after varying degrees of micrococcal nuclease (MNase) digestion, followed by isolation of mononucleosomal DNA and sequencing. Three replicates of each strain (9 samples) were subjected to Illumina sequencing.

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: kaifu chen

PROVIDER: E-GEOD-37465 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Global Regulation of Nucleosome Organization And Transcription By The Yeast Ssn6-Tup1 Corepressor (expression)

Project description:The yeast Ssn6-Tup1 complex regulates gene expression through a variety of mechanisms, including positioning of nucleosomes over promoters of some target genes to limit accessibility to the transcription machinery. To further define the functions of Ssn6-Tup1 in gene regulation and chromatin remodeling, we performed genome-wide profiling of changes in nucleosome organization and gene expression that occur upon loss of SSN6 or TUP1, and observed extensive nucleosome alterations in both promoters and gene bodies of derepressed genes. Our improved nucleosome profiling and analysis approaches revealed low-occupancy promoter nucleosomes (P nucleosomes) at locations previously defined as nucleosome-free regions. In the absence of SSN6 or TUP1, this P nucleosome is frequently lost, whereas nucleosomes are gained at -1 and +1 positions, accompanying up-regulation of downstream genes. Our analysis of public ChIP-seq data revealed that Ssn6 and Tup1 preferentially bind TATA-containing promoters, which are also enriched in genes derepressed upon loss of SSN6 or TUP1. These results suggest that stabilization of the P nucleosome on TATA-containing promoters may be a central feature of the repressive chromatin architecture created by the Ssn6-Tup1 corepressor, and that releasing the P nucleosome contributes to gene activation.

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Global Regulation of Nucleosome Organization And Transcription By The Yeast Ssn6-Tup1 Corepressor (MNase-Seq)

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Global Regulation of Nucleosome Organization And Transcription By The Yeast Ssn6-Tup1 Corepressor

Project description:This SuperSeries is composed of the following subset Series: GSE37465: Global Regulation of Nucleosome Organization And Transcription By The Yeast Ssn6-Tup1 Corepressor (MNase-Seq) GSE37466: Global Regulation of Nucleosome Organization And Transcription By The Yeast Ssn6-Tup1 Corepressor (expression) Refer to individual Series

2012-10-10 | E-GEOD-37467 | biostudies-arrayexpress

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Nucleosome loss leads to global transcriptional upregulation and genomic instability during yeast replicative aging

Project description:All eukaryotic cells divide a finite number of times, termed replicative aging, but the reason for this is not clear. Consistent with the decreased total histone protein levels in aged Saccharomyces cerevisiae, which is a cause of aging (1), we find that nucleosome occupancy decreases 50% across the whole genome during replicative aging by spike-in controlled MNase sequencing. Nucleosomes become fuzzier or move to sequences predicted to better accommodate histone octamers. All yeast genes are induced during aging. Genes that are repressed in young cells are most induced, accompanied by nucleosome loss from their promoters that have unique chromatin organization. Contrary to the loss of mitochondrial function during aging, mitochondrial DNA content increases and unprecedented levels of large-scale chromosomal alterations and increased retrotransposition are observed. Mnase-Seq experiments were carried out for young yeast, old yeast, and old yeast with histone over expression, 3 replicates were done for each category. RNA-Seq were carried out for the same categories of yeast cells but with 2 replicates for each. Genome-Seq were done for the young and old yeast with 2 replicates for each.

2014-02-26 | E-GEOD-47023 | biostudies-arrayexpress

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Project description:We determined genome-wide nucleosome occupancy in mouse embryonic stem cells and their neural progenitor and embryonic fibroblast counterparts to assess features associated with nucleosome positioning during lineage commitment. Cell type and protein specific binding preferences of transcription factors to sites with either low (e.g. Myc, Klf4, Zfx) or high (e.g. Nanog, Oct4 and Sox2) nucleosome occupancy as well as complex patterns for CTCF were identified. Nucleosome depleted regions around transcription start and termination sites were broad and more pronounced for active genes, with distinct patterns for promoters classified according to their CpG-content or histone methylation marks. Throughout the genome nucleosome occupancy was dependent on the presence of certain histone methylation or acetylation modifications. In addition, the average nucleosome-repeat length increased during differentiation by 5-7 base pairs, with local variations for specific genomic regions. Our results reveal regulatory mechanisms of cell differentiation acting through nucleosome repositioning. We have determined genome-wide nucleosome position maps in mouse embryonic stem cells (ESCs), neural progenitor cells (NPCs) derived from these ESCs by retinoic acid induced differentiation as well as mouse embryonic fibroblasts (MEFs) from the corresponding mouse strain

2012-10-21 | E-GEOD-40910 | biostudies-arrayexpress

The stress response factors Yap6, Cin5, Phd1, and Skn7 direct targeting of the conserved co-repressor Tup1-Ssn6

Project description:The budding yeast transcriptional corepressor Tup1-Ssn6 is a model for studying similar repressosome complexes in multicellular eukaryotes. Tup1-Ssn6 does not bind DNA directly, but is directed to individual promoters by one or more DNA-binding proteins, referred to as Tup1 recruiters. We determined the genomic distribution of Tup1 and Ssn6 by ChIP-chip and found that most loci bound by Tup1-Ssn6 could not be explained by co-occupancy with a known recruiting cofactor. Furthermore, we found that individual deletions of known Tup1 recruiters did not significantly alter Tup1 binding profile. These two observations suggest that Tup1 recruitment typically depends on multiple recruiting cofactors, and that new Tup1 recruiting proteins remain to be discovered. To identify new recruiting proteins we computationally screened for factors with binding patterns similar to the observed Tup1-Ssn6 genomic distribution. Four top candidates, Cin5, Skn7, Phd1, and Yap6, all known to be associated with stress response gene regulation, were experimentally confirmed to physically interact with Tup1 and/or Ssn6. Incorporating these new cofactors with previously characterized cofactors now accounts for the majority of Tup1 binding across the genome, and expands our understanding of the mechanism by which Tup1-Ssn6 is directed to its targets.

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The stress response factors Yap6, Cin5, Phd1, and Skn7 direct targeting of the conserved co-repressor Tup1-Ssn6

2011-03-01 | E-GEOD-26311 | biostudies-arrayexpress

Effects of Histone H3 depletion on nucleosome occupancy and positioning through the S. cerevisiae genome [single-end MNase-seq]

Project description:Experiments performed over the past three decades have shown that nucleosomes are transcriptional repressors. In Saccharomyces cerevisiae, depletion of histone H4 results in the genome-wide transcriptional de-repression of hundreds genes. The mechanism of de-repression is hypothesized to be rooted directly in chromatin changes. To test this, we reproduced classical H4 depletion experiments by conditional repression of all histone H3 transcription, which depletes the supply of nucleosomes in vivo. RNA-seq results were consistent with the earlier studies, but much more sensitive, revealing nearly 2500 de-repressed genes. Changes in chromatin organization were determined by MNase-seq. Nucleosomes that were preferentially retained occurred in regions of high DNA-encoded nucleosome affinity, and were marked with H3K36me2, which is linked to transcription elongation. Nucleosomes harboring acetyl marks or that contained the variant histone H2A.z were preferentially lost. Genes that were de-repressed lost or rearranged nucleosomes at their promoter, but not in the gene body. Therefore, a combination of DNA-encoded nucleosome stability and nucleosome composition dictates which nucleosomes will be lost under conditions of limiting histone protein. This, in turn, governs which genes will experience a loss of regulatory fidelity. MNase-seq experiments consist of three wildtype (1 single-end and 2 paired-end) and four mutant (DCB200.1/H3 shutoff; 2 single-end, 2 paired-end) replicates. Each replicate contains two timepoints reflecting chromatin immediately after ("O hours") and 3 hours after transition to media containing dextrose. RNA-seq data includes three replicates from wildtype or H3 depleted cells after 3 hours in media containing dextrose.

2012-09-26 | E-GEOD-29291 | biostudies-arrayexpress

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