Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

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

ABSTRACT: 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.

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Jason Lieb

PROVIDER: E-GEOD-29291 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

In vivo effects of histone H3 depletion on nucleosome occupancy and position in Saccharomyces cerevisiae.

Gossett Andrea J AJ Lieb Jason D JD

PLoS genetics 20120621 6

Previous studies in Saccharomyces cerevisiae established that depletion of histone H4 results in the genome-wide transcriptional de-repression of hundreds of genes. To probe the mechanism of this transcriptional de-repression, we depleted nucleosomes in vivo by conditional repression of histone H3 transcription. We then measured the resulting changes in transcription by RNA-seq and in chromatin organization by MNase-seq. This experiment also bears on the degree to which trans-acting factors and ...[more]

PMID: 22737086

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Project description:Maintenance of the correct level and organization of nucleosomes is crucial for genome function. Here we uncover a role for a conserved bromodomain AAA-ATPase, Abo1, in maintenance of nucleosome architecture in fission yeast. Cells lacking abo1+ experience both a reduction and mis-positioning of nucleosomes at transcribed sequences in addition to increased intragenic transcription, phenotypes that are hallmarks of defective chromatin re-establishment behind RNA polymerase II. Abo1 is recruited to gene sequences and associates with histone H3 and the histone chaperone FACT. Furthermore, the distribution of Abo1 on chromatin is disturbed by impaired FACT function. The role of Abo1 extends to some promoters and also to silent heterochromatin. Abo1 is recruited to pericentromeric heterochromatin independently of the HP1 ortholog, Swi6, where it enforces proper nucleosome occupancy. Consequently, loss of Abo1 alleviates silencing and causes elevated chromosome mis-segregation. We suggest that Abo1 provides a histone chaperone function that maintains nucleosome architecture genome-wide. A chromatin-seq/MNase-seq approach called Chromatin Particle Spectrum Analysis (Kent et al., (2011) Nucleic Acids Res. 39:e26) was used to map and compare nucleosome position in wild-type (strain 972) and isogenic abo1 knock-out (strain HM463) fission yeast cells. For each strain, three independent in vivo MNase digest bio-reps were performed and the purified DNA pooled. CPSA was performed using paired-end mode Illumina technology with pooled samples multiplexed over two HiSeq2000 lanes. Each CPSA paired read describes a microcococcal nuclease (MNase) resistant DNA species from chromatin, with the insert-size equivalent to the size of DNA protection. For each strain type, two analysed data sets are provided here: one listing the genomic distribution of MNase-protected DNAs of 150bp (â150bp CPSA size classâ) and corresponding to mono-nucleosomes; the other listing the genomic distribution of MNase-protected DNAs of 300bp (â300bp CPSA size classâ) and corresponding to di-nucleosomes.

Project description:Nucleosomes in all eukaryotes examined to date adopt a characteristic architecture within genes and play fundamental roles in regulating transcription, yet the identity and precise roles of many of the trans-acting factors responsible for the establishment and maintenance of this organization remain to be identified. We profiled a compendium of 50 yeast strains carrying conditional alleles or complete deletions of genes involved in transcriptional regulation, histone biology and chromatin remodeling, as well as compounds that target transcription and histone deacetylases, to assess their respective roles in nucleosome positioning and transcription. We find that nucleosome patterning in genes is affected by many factors including the CAF-1 complex, Spt10 and Spt21, in addition to previously reported remodeler ATPases and histone chaperones. Disruption of these factors or reductions in histone levels led genic nucleosomes to assume positions more consistent with their intrinsic sequence preferences, with pronounced and specific shifts of the +1 nucleosome relative to the transcription start site. These shifts of +1 nucleosomes appear to have functional consequences, as several affected genes in Ino80 mutants exhibited altered expression responses. Our parallel expression profiling compendium revealed extensive transcription changes in intergenic and antisense regions, most of which occur in regions with altered nucleosome occupancy and positioning. We show that the nucleosome-excluding transcription factors Reb1, Abf1, Tbf1, and Rsc3 suppress cryptic transcripts at their target promoters, while a combined analysis of nucleosome and expression profiles identified 36 novel transcripts that are normally repressed by Tup1/Cyc8. Our data confirm and extend the roles of chromatin remodelers and chaperones as major determinants of genic nucleosome positioning and these data provide a valuable resource for future studies. We examined 50 single-gene loss-of-function strains, comprised of gene deletions (del) and temperature-sensitive (ts) or tetracycline promoter-shutoff (tet) alleles. These genes were selected based on their known or potential role in nucleosome biology and include remodeler ATPases and chaperones, histones and histone modifiers, transcription and elongation factors, and components of RNA polymerase I and II. The compendium also includes 4 compounds targeting transcription and histone deacetylases, as well as a histone depletion time course performed with a strain in which H4 gene expression is exclusively under the control of a GAL1 promoter. Genome-wide nucleosome occupancy profiles were generated using Affymetrix Tiling arrays with probes spaced every 4 bp [PMID:16569694], or next-generation sequencing. Identically prepared samples for each strain and treatment were analyzed on the same tiling arrays for strand-specific expression differences. Each compendium condition was compared to a matched wild-type (WT) reference grown in parallel.

Dataset Information

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

Publications

In vivo effects of histone H3 depletion on nucleosome occupancy and position in Saccharomyces cerevisiae.

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