Abstract
Polycomb group (PcG) proteins bind and regulate hundreds of genes. Previous evidence has suggested that long-range chromatin interactions may contribute to the regulation of PcG target genes. Here, we adapted the Chromosome Conformation Capture on Chip (4C) assay to systematically map chromosomal interactions in Drosophila melanogaster larval brain tissue. Our results demonstrate that PcG target genes interact extensively with each other in nuclear space. These interactions are highly specific for PcG target genes, because non-target genes with either low or high expression show distinct interactions. Notably, interactions are mostly limited to genes on the same chromosome arm, and we demonstrate that a topological rather than a sequence-based mechanism is responsible for this constraint. Our results demonstrate that many interactions among PcG target genes exist and that these interactions are guided by overall chromosome architecture.
Highlights
Polycomb group (PcG) proteins are evolutionary conserved and important epigenetic regulators that bind and modify chromatin
Our results indicate that Polycomb domains (PcDs) extensively and interact with each other, yet these interactions are topologically constrained by the overall chromosome architecture
Such a longrange interaction was found in Drosophila for two genomic loci that are known to be bound by the Polycomb Repressive Complex
Summary
Polycomb group (PcG) proteins are evolutionary conserved and important epigenetic regulators that bind and modify chromatin. They repress transcription of Homeotic genes [1] and many other key regulators of development [2,3,4,5,6]. PcG proteins are thought to mediate gene silencing by changing the structure of chromatin, but the exact molecular mechanisms are not yet fully understood. The Pleiohomeotic Repressive Complex binds directly to DNA sequences. There are two Polycomb Repressive Complexes (PRC1 and PRC2) that bind indirectly to DNA via protein-protein interactions. The chromodomain of Polycomb (PC), one of the components of PRC1, binds to this mark
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