Transcription Initiation Patterns Indicate Divergent Strategies for Gene Regulation at the Chromatin Level (original) (raw)
Figure 6
Distinct Nucleosome Organization Is Conserved in Insects.
(A) Fruit fly H2A.Z profiles show that BP and WP promoters had increased H2A.Z levels (p<10E-07). Nucleosomes in BP and WP promoters had a more precise spacing, with an average separation of 170 bp and deviations of up to 10 bp, compared to a mean distance of 183 bp between H2A.Z peaks at NP promoters, with deviations of up to 33 bp. (B) Differences between promoter classes were less pronounced in the available lower-resolution Drosophila bulk nucleosome data, with a slight shift compared to H2A.Z as originally reported [6]. (C) Average bulk nucleosome occupancy profiles were computed by an in silico model, which assigned the predicted probability that a nucleosome was present at any given location [34]. An average occupancy score of .5 indicated no preference for nucleosome presence or absence, as reflected in the scores at random intergenic locations. A clear separation of NP, BP, and WP profiles was observed, and the NFR for NP promoters was clearly much less pronounced; all predicted profiles were significantly different from each other (p<10E-09). (D) NP promoters had noticeably higher levels of pol II binding than BP and WP promoters (12–16 hr embryos). (E,F) Stalled NP, BP, and WP promoters in Drosophila mixed stages embryos (0–16 hr) maintained the same associations to H2A.Z and bulk nucleosomes as observed for the set of all actively transcribed 0–12 hr promoters.