Project description:This SuperSeries is composed of the following subset Series: GSE14649: DCC binding and function (Expression Analysis) GSE14650: DCC binding and function (ChIP-chip: SDC-3, MIX-1, DPY-27, Mock) GSE14651: DCC binding and function (ChIP-chip: DPY-27) GSE14652: DCC binding and function (ChIP-chip: SDC-2) GSE14653: DCC binding and function (ChIP-chip: SDC-3, DPY-27, Mock) Refer to individual Series
Project description:Here we exploit the essential process of X-chromosome dosage compensation to elucidate basic mechanisms that control the assembly, genome-wide binding, and function of gene regulatory complexes that act over large chromosomal territories. We demonstrate that a subunit of C. elegans MLL/COMPASS, a gene-activation complex, acts within the dosage compensation complex (DCC), a condensin complex, to target the DCC to both X chromosomes of hermaphrodites and thereby reduce chromosome-wide gene expression. The DCC binds to two categories of sites on X: rex sites that recruit the DCC in an autonomous, sequence- dependent manner, and dox sites that reside primarily in promoters of expressed genes and bind the DCC robustly only when attached to X. We find that DCC mutants that abolish rex-site binding do not eliminate dox-site binding, but instead reduce it to the level observed at autosomal binding sites in wild-type animals. Changes in DCC binding to these non-rex sites occur throughout development and correlate with transcriptional activity of adjacent genes. Moreover, autosomal DCC binding is enhanced by rex-site binding in cis in X-autosome fusion chromosomes. Thus, dox and autosomal sites exhibit similar binding properties. Our data support a model for DCC binding in which low-level DCC binding at dox and autosomal sites is dictated by intrinsic properties correlated with high transcriptional activity. Sex-specific DCC recruitment to rex sites then greatly elevates DCC binding to dox sites in cis, which lack intrinsically high DCC affinity on their own. We also show here that the C. elegans DCC achieves dosage compensation through its effects on transcription. ChIP-chip experiments using antibodies against DPY-27, SDC-3, DPY-30, DPY-26, MIX-1, SMC-4, ASH-2 in wild-type embryos. ChIP-chip experiments using antibodies against SDC-3, DPY-27, DPY-30, ASH-2, and IgG in different DCC mutants. ChIP-chip experiments using antibodies against RNA Pol II (hypophosphorylated and S2 and S5) in wild type and sdc-2 partial loss of function mutants.
Project description: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
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.
Project description:In many species, a dosage compensation complex (DCC) is targeted to X chromosomes of one sex to equalize levels of X gene products between males (1X) and females (2X). Here we identify cis-acting regulatory elements that target the C. elegans X chromosome for repression by the DCC. The DCC binds to discrete, dispersed sites on X of two types. rex sites recruit the DCC in an autonomous, DNA sequence-dependent manner using a 12 bp consensus motif that is enriched on X. This motif is critical for DCC binding, is clustered in rex sites, and confers much of X-chromosome specificity. Motif variants enriched on X by 3.8-fold or more are highly predictive (95%) for rex sites. In contrast, dox sites lack the X-enriched variants and cannot bind the DCC when detached from X. dox sites are more prevalent than rex sites and, unlike rex sites, reside preferentially in promoters of some expressed genes. These findings fulfill predictions for a targeting model in which the DCC binds to recruitment sites on X and disperses to discrete sites lacking autonomous recruitment ability. To relate DCC binding to function, we identified dosage-compensated and non-compensated genes on X. Unexpectedly, many genes of both types have bound DCC, but many do not, suggesting the DCC acts over long distances to repress X gene expression. Remarkably, the DCC binds to autosomes, but at far fewer sites and rarely at consensus motifs. DCC disruption causes opposite effects on expression of X and autosomal genes. The DCC thus acts at a distance to impact expression throughout the genome. Experiment Overall Design: For microarray analysis, the nematode strains and number of experiments was as follows: TY2222, her-1(hv1y101); xol-1(y9) sdc-2(y74) unc-9(e101), XO embryos (8 biological replicas and 6 wild-type XX embryos controls ), dpy-27(y57) XX embryos (3 biological replicas and 3 wild-type XX embryos controls), and sdc-2(y93, RNAi) XX embryos (3 biological replicas and 3 wild-type XX embryos controls).