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High nucleosome occupancy is encoded at X-linked gene promoters in C. elegans.

ABSTRACT: We mapped nucleosome occupancy by paired-end Illumina sequencing in C. elegans embryonic cells, adult somatic cells, and a mix of adult somatic and germ cells. In all three samples, the nucleosome occupancy of gene promoters on the X chromosome differed from autosomal promoters. While both X and autosomal promoters exhibit a typical nucleosome-depleted region upstream of transcript start sites and a well-positioned +1 nucleosome, X-linked gene promoters on average exhibit higher nucleosome occupancy relative to autosomal promoters. We show that the difference between X and autosomes does not depend on the somatic dosage compensation machinery. Instead, the chromatin difference at promoters is partly encoded by DNA sequence, because a model trained on nucleosome sequence preferences from S. cerevisiae in vitro data recapitulate nearly completely the experimentally observed difference between X and autosomal promoters. The model predictions also correlate very well with experimentally determined occupancy values genome-wide. The nucleosome occupancy differences observed on X promoters may bear on mechanisms of X chromosome dosage compensation in the soma, and chromosome-wide repression of X in the germline.

SUBMITTER: Ercan S

PROVIDER: S-EPMC3032927 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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High nucleosome occupancy is encoded at X-linked gene promoters in C. elegans.

Ercan Sevinç S Lubling Yaniv Y Segal Eran E Lieb Jason D JD

Genome research 20101222 2

We mapped nucleosome occupancy by paired-end Illumina sequencing in C. elegans embryonic cells, adult somatic cells, and a mix of adult somatic and germ cells. In all three samples, the nucleosome occupancy of gene promoters on the X chromosome differed from autosomal promoters. While both X and autosomal promoters exhibit a typical nucleosome-depleted region upstream of transcript start sites and a well-positioned +1 nucleosome, X-linked gene promoters on average exhibit higher nucleosome occup ...[more]

PMID: 21177966

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Project description:In eukaryotic organisms, packaging of DNA into nucleosomes controls gene expression by regulating access of the promoter to transcription factors. The human malaria parasite Plasmodium falciparum encodes relatively few transcription factors, while extensive nucleosome remodeling occurs during its replicative cycle in red blood cells. These observations point towards an important role of the nucleosome landscape in regulating gene expression. However, the relation between nucleosome positioning and transcriptional activity has thus far not been explored in detail in the parasite.Here, we analyzed nucleosome positioning in the asexual and sexual stages of the parasite's erythrocytic cycle using chromatin immunoprecipitation of MNase-digested chromatin, followed by next-generation sequencing. We observed a relatively open chromatin structure at the trophozoite and gametocyte stages, consistent with high levels of transcriptional activity in these stages. Nucleosome occupancy of genes and promoter regions were subsequently compared to steady-state mRNA expression levels. Transcript abundance showed a strong inverse correlation with nucleosome occupancy levels in promoter regions. In addition, AT-repeat sequences were strongly unfavorable for nucleosome binding in P. falciparum, and were overrepresented in promoters of highly expressed genes.The connection between chromatin structure and gene expression in P. falciparum shares similarities with other eukaryotes. However, the remarkable nucleosome dynamics during the erythrocytic stages and the absence of a large variety of transcription factors may indicate that nucleosome binding and remodeling are critical regulators of transcript levels. Moreover, the strong dependency between chromatin structure and DNA sequence suggests that the P. falciparum genome may have been shaped by nucleosome binding preferences. Nucleosome remodeling mechanisms in this deadly parasite could thus provide potent novel anti-malarial targets.

Dataset Information

High nucleosome occupancy is encoded at X-linked gene promoters in C. elegans.

Publications

High nucleosome occupancy is encoded at X-linked gene promoters in C. elegans.

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