Figure 1

HP1a has dual roles in regulating transcription of Drosophila genes. (A) mRNA levels for six genes in 2–3 h embryos from Su(var)2-5 ⁰⁵ /CyO parents relative to Ore R (set to one, dotted line). Asterisks show changes which are significant relative to Ore R (***P value <0.0005); for tsr and Sxl the difference is not significant. (B) In situ hybridization for h and Ubx in embryos from Ore R or Su(var)2-5 ⁰⁵/CyO parents. Top two rows show two different stages as the seven stripes of h resolve; in both cases, embryos with a decrease or increase in signal relative to wild-type are seen in the Su(var)2-5 ⁰⁵ class. Third row shows similar effects on Ubx which had a larger disparity. Weaker, stronger, and normal expression embryos 20:41:22 for h; 10:16:8 for Ubx; proportions of approximately 1:2:1. Sxl, Sex-lethal; Ubx, Ultrabithorax; hb, hunchback; tsr, twinstar; bnk, bottleneck.