Expression of histone genes during heat shock and in arsenite-treated Drosophila Kc cells.

In Drosophila Kc cultured cell lines, heat shock induces an increased synthesis of one of the core histones, H2B. This is accompanied by a reduction in the rate of synthesis of H1 and the other core histones, suggesting a noncoordinated expression of histones during heat shock. Arsenite which has a heat-shock mimicking effect does not induce an increase in the synthesis of H2B. The increased expression of H2B during heat shock shows a temperature dependency similar to that of the low molecular weight heat-shock proteins being observed at temperatures higher than 33 degrees C. A full heat-shock response is observed after a short 15-min shock at 37 degrees C, suggesting a rapid transcriptional response of the H2B gene and possibly a decreased transcription of the other histones and (or) an accelerated decay of their corresponding mRNAs. This increased synthesis of H2B seems under transcriptional control since it can be inhibited, like the other major heat-shock proteins, by the addition of actinomycin D.