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ChIP-chip analysis of Dosage Compensation complex members SDC-3 and DPY-27 in C elegans wild type embryos.

ABSTRACT: Among organisms with chromosome-based mechanisms of sex determination, failure to equalize expression of X-linked genes between the sexes is typically lethal. In C. elegans, XX hermaphrodites halve transcription from each X chromosome to match the output of XO males1. Here, we mapped the binding location of the condensin homolog DPY-27 and the zinc finger protein SDC-3, two components of the C. elegans dosage compensation complex (DCC)2,3. Strong foci of DCC binding were observed on X, around which broader regions of localization were centered. Binding foci, but not adjacent regions of localization, were distinguished by clusters of a stereotypic 10-bp DNA sequence, suggesting a recruitment-and-spreading mechanism for X recognition. In contrast to the Drosophila DCC, the C. elegans DCC was bound preferentially upstream of genes, suggesting modulation of transcriptional initiation and transcription-coupled spreading. A mechanism for tuning DCC activity at specific loci was indicated by stronger DCC binding upstream of genes with high transcriptional activity. These data provide a basis for understanding how proteins involved in higher-order chromosome dynamics can regulate transcription at individual loci. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Keywords: ChIP-chip dosage compensation complex

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE6739 | GEO | 2007/02/11

REPOSITORIES: GEO

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Cooperation between a hierarchical set of recruitment sites specifically targets the C. elegans dosage compensation complex to the X chromosomes.

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Project description:In C. elegans, a condensin-like protein complex associates specifically with both X chromosomes of XX animals to execute dosage compensation. Dosage Compensation Complex (DCC) reduces the level of transcripts arising from each of the two X chromosomes. Recruitment to X is specified in part by discrete DNA sequence motifs, but following recruitment, the DCC is targeted to the promoters of individual active genes by an unknown mechanism. Here, we investigated three outstanding questions regarding the molecular mechanism of DCC recruitment and spreading along X. By examining the genome-wide binding patterns of several DCC subunits in different stages of C. elegans development, and in strains harboring X:Autosome chromosomal fusions, we provide evidence that: (1) DCC binding is dynamically specified according to gene activity during development (2) The condensin-like subunits of the DCC spread from recruitment sites to active promoters more readily than the non-conserved SDC subunits, which are involved in initial X-targeting and (3) the mechanism of DCC spreading is independent of X-chromosome DNA sequence, and will proceed onto any active promoter near a recruitment site. Our results contribute to understanding how chromatin complexes can be targeted to achieve domain-scale transcriptional regulation during development. ChIP-chip analysis of SDC-2, DPY-26 and MIX-1 were done in C elegans N2 embryos. DPY-27 and RNA Polymerase II ChIP-chip were performed in N2 L4s. DPY-27 ChIP-chip in X-autosome fusions were done, X chromosome fused to either V (YPT47), II (YPT41) or I (11dh). RNA abundance analysis in N2, YPT41 and YPT47 embryos are included.

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