Distinct Polycomb Response Elements control chromatin state and gene activation of the vestigial gene

Patterned expression of many developmental genes is thought to rely on chromatin-mediated repression. Regulatory DNA sequences called Polycomb Response Elements (PREs) play critical roles in repression. While PREs in transgenes can nucleate trimethylation on lysine 27 of the histone H3 tail (H3K27me3), none have been demonstrated to be necessary at endogenous chromatin domains. This is thought to be due to the fact that most endogenous H3K27me3 domains contain many PREs, and individual PREs may be redundant. We show here that PREs near the wing selector gene vestigial have distinctive roles at their endogenous locus, even though both PREs are repressors in transgenes. First, a PRE near the promoter is required for vestigial activation and not for repression. Second, only the distal PRE contributes to H3K27me3, but even removal of both PREs does not eliminate H3K27me3 across the vestigial domain. Thus, endogenous chromatin domains appear to be intrinsically marked by H3K27me3, and PREs can enhance this chromatin modification at inactive genes. Overall design: We dissected Drosophila larval tissues and generated chromatin profiles using Cleavage under targets and Release using nuclease (CUT&RUN), in which controlled cleavage by an antibody-tethered micrococcal nuclease releases specific protein-DNA complexes into the supernatant for paired-end sequencing.