Figure 5

Drosophila gene promoters in early embryos are bivalently marked. ChIP data for H3K27me3 and H3K4me3 for Ubx, hb, Sxl, nullo, bnk, h, and tsr. Note scales for each gene. Ubx is bivalent in both 0–2 and 1–3 h embryos before it is transcribed; hb begins expression toward the end of the 0–2 h window. Sxl_Pe and h begin transcription in cycle 12 (approximately 110 min). nullo and bnk are expressed globally and begin transcription in cycle 11 (approximately 100 min). The large maternal deposit for tsr (actin depolymerizing protein cofilin) masks this promoter’s timing, although its mRNA increases at 2–4 h suggesting embryonic transcription. Cofilin is required globally and the tsr promoter has dual marks, albeit low H3K27me3 levels, in all 3 windows. (ModENCODE temporal expression data). Signal is above NI in all cases. Error bars represent ± SEM. Ubx, Ultrabithorax; hb, hunchback; Sxl, Sex-lethal; bnk, bottleneck; h, hairy; tsr, twinstar.