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Dataset Information

Nucleosome positioning for 4 yeast species

ABSTRACT: We describe the genome-wide nucleosome profiles of four related yeast species. All species display the same global organization features first described in S. cerevisiae: a stereotypical nucleosome organization along genes, and the classification of promoters into these which contain or lack a pronounced Nucleosome Depleted region (NDR), with the latter displaying a more dynamic pattern of gene expression. This global similarity, however, does not reflect a static evolutionary pattern, as nucleosome positioning at specific genes diverged rapidly leaving practically no similarity between S. cerevisiae and C. glabrata orthologs (~50 Myr). We show that this rapid divergence in nucleosome positioning contrasts a conserved pattern of gene expression, consistent with the idea that divergence of nucleosome patterns has a limited effect on gene expression as many different configurations can support the same regulatory outcome. Nucleosomes from 4 different yeast species were isolated and sequenced using the Illumina GAII platform. Replicates were performed for 3 of the species

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Kyle Tsui

PROVIDER: E-GEOD-23577 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Evolution of nucleosome occupancy: conservation of global properties and divergence of gene-specific patterns.

Tsui Kyle K Dubuis Sébastien S Gebbia Marinella M Morse Randall H RH Barkai Naama N Tirosh Itay I Nislow Corey C

Molecular and cellular biology 20110906 21

To examine the role of nucleosome occupancy in the evolution of gene expression, we measured the genome-wide nucleosome profiles of four yeast species, three belonging to the Saccharomyces sensu stricto lineage and the more distantly related Candida glabrata. Nucleosomes and associated promoter elements at C. glabrata genes are typically shifted upstream by ∼20 bp, compared to their orthologs from sensu stricto species. Nonetheless, all species display the same global organization features first ...[more]

PMID: 21896781

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Project description:We produced a genome-wide map of the distribution of macroH2A1 histone variants in mouse liver chromatin using high-throughput sequencing of DNA from macroH2A1 nucleosomes. Although macroH2A1 nucleosomes are widely distributed across the genome, their local concentration varies over a range of 100-fold or more. The transcribed regions of most active genes are depleted of macroH2A1, with many showing depletion of 3-fold or more. The inactive X chromosome appears to have relatively uniform macroH2A1 enrichment that averages approximately 3.9-fold, but most genes that are known to escape from X inactivation do not show this enrichment. We used macroH2A1 depletion to identify additional genes that escape X inactivation, but overall, our map supports the idea that relatively few genes escape in the mouse. The map also helped identify genes that appear to be direct targets of macroH2A1-mediated repression. MacroH2A1 nucleosomes were purified from female mouse liver chromatin by thiol-affinity chromatography (Mol. Cell Biol. 26, 4410 (2006)) and their distribution was compared to that of the bulk nucleosomes used as the starting material for the purification. Nucleosomal DNA from two independent preparations was pooled and mononucleosomal DNA was prepared from both macroH2A1 and starting material nucleosomes. Each preparation used 8 to 10 livers from 8 to 10 week old female mice. For the relative macroH2A1 content file (see supplementary file), we used tools in the rna-seq workflow of Partek Genomics Suite (version 6.5b, 6.09.0806, Partek Inc.) to calculate the relative macroH2A1 content of individual genes. This program counts and normalizes hits in predefined regions specified in a refFlat file. The gene list was the Mouse build 8 version of refFlat.txt obtained from the UCSC Genome site. All exon information was stripped from the refFlat.txt file, which left only the start and stop sites for the genes. Normalized RPKM (reads per kilobase per million reads) values were compared to calculate fold change and FDR-adjusted p-values for each transcript.

Project description:Methylation of DNA at CpG dinucleotides represents one of the most important epigenetic mechanisms involved in the control of gene expression in vertebrate cells. In this report, we conducted high-throughput nucleosome reconstitution experiments on 572 KB of human DNA and 668 KB of mouse DNA that was unmethylated or methylated in order to investigate the effects of this epigenetic modification on the positioning and stability of nucleosomes. The DNA loci from both species contained the genes that encode the serum albumin family, the MYC protein, and the tumor suppressor p53. The results demonstrated that a small subset of nucleosomes positioned by nucleotide sequence was sensitive to methylation where the modification increased the affinity of these sequences for the histone octamer. The features that distinguished these nucleosomes from the bulk of the methylation-insensitive nucleosomes were an increase in the frequency of CpG dinucleotides and a unique rotational orientation of CpGs such that their minor grooves tended to face toward the histones in the nucleosome rather than away. We propose that these features serve to enhance the affinity of methylated DNA for the histone octamer and that this effect could be involved in gene regulatory mechanisms such as silencing. These methylation-sensitive nucleosomes were preferentially associated with exons as compared to introns while unmethylated CpG islands near transcription start sites became enriched in nucleosomes upon methylation. The results of this study suggest that the effects of DNA methylation on nucleosome stability in vitro can recapitulate what has been observed in the cell and provide a direct link between DNA methylation and the structure and function of chromatin. For the human data, there were 3 unmethylated nucleosome replicates, 2 methylated nucleosome replicates, an unmethylated MNase control, and an unmethylated sonicated control. For the mouse data, there were 2 unmethylated nucleosome replicates, 2 methylated nucleosome replicates, an unmethylated MNase control, a methylated MNase control, and an unmethylated sonicated control.

Dataset Information

Nucleosome positioning for 4 yeast species

Publications

Evolution of nucleosome occupancy: conservation of global properties and divergence of gene-specific patterns.

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