Fig. 4.

Class IV CBP regions with histone acetylation represent functional insulators. a Enrichment of different histone acetylations within 500 bp around the CBP peak centres in Class IV. The Class IV regions were divided into two sub-classes, a and b, based on a PCA using all histone modifications (n = 27). Error bars represent 95 % confidence intervals. c, d Average enrichment of the H3K27me3 mark within 10 kb around the CBP peak centres in the two sub-classes of Class IV CBP regions (sub-class with high levels c and low levels d of acetylation). Only Class IV regions within 10 kb of an H3K27me3 domain were considered. The regions were oriented so that the highest level of H3K27me3 was to the right of the CBP peak centre (vertical dashed line) in the plots. Values were scaled so that a value of zero corresponds to the genomic mean and a value of one to the genomic maximum. e, f ChIP-qPCR (3–4 biological replicates) using H3K27me3 antibodies (normalized to H3) after 30 min of CBP HAT inhibition (C646, in brown) and control treatment (C37, in orange) at regions surrounding Class IV sites with high acetylation (e, regions 1–3) and low acetylation (f, region 4). Regions are oriented so that the left pair of primers (x.1) are located at the side with lower acetylation [as in (c, d)]. Error bars represent standard error of the mean