Physical and functional interaction between the SET1/COMPASS complex component CFP-1/CXXC and a Sin3S HDAC complex

The CFP1/CXXC protein targets SET1/COMPASS complexes to non-methylated CpG rich promoter regions to implement tri-methylation of histone H3 Ly4 (H3K4me3). Although H3K4me3 is widely associated with gene expression, the effects of CFP1 loss depend on chromatin context. Little is known about how CFP1 binding is coordinated with other chromatin factors. Using a proteomics approach, we establish a link between C. elegans CFP1 and a small Rpd3/Sin3 histone deacetylase (HDAC) complex (Sin3S). Mutants of CFP-1, SIN-3, and the catalytic subunit SET-2/SET1 have similar phenotypes and misregulate the expression of common genes. CFP-1 directly interacts with SIN-3 through a region including the conserved PAH1 domain, and contributes to recruitment of SIN-3 and the Sin3S subunit HDA-1 to H3K4me3 enriched promoters. Our results reveal a novel role for CFP-1 in mediating interaction between SET1/COMPASS and a Sin3 HDAC small complex at promoters, with implications for the coordinate regulation of gene expression by chromatin- associated complexes with distinct activities. Overall design: ChIP-seq was used to profile H3K4me3, SIN-3, and HDA-1 in wild-type, cfp-1, and set-2 mutant C. elegans embryos