RNA polymerase II transcribes all of the heat shock induced genes of Drosophila melanogaster.

Heat shock of Drosophila melanogaster induces the transcription of a small number of RNAs. Some of these encode protein products, but not all. We have investigated whether the several induced RNAs are transcribed by RNA polymerase II or by some other RNA polymerase. Immunochemical staining of polytene chromosomes indicates that, on heat shock, RNA polymerase II is relocalized; it "migrates" from previously-active transcription sites to the heat shock induced loci. All heat shock induced puffs show immunochemical staining. Such staining correlates with RNA polymerase II activity as judged by the sensitivity of RNA synthesis at these sites to low concentrations of alpha-amanitin. Thus the protein-coding and non-protein-coding heat shock-induced RNAs are transcribed by this polymerase specifically. We have also identified several non-puffed chromosomal sites at which RNA synthesis is induced by heat shock.