Heat-induced degradation of PER and TIM in Drosophila bearing a conditional allele of the heat shock transcription factor gene.

Heat pulses elicit dramatic and rapid decreases in the levels of the D. melanogaster period (per) and timeless (tim) proteins (i.e., PER and TIM). To investigate the possible role of the heat shock pathway in this response, we used Drosophila bearing a conditional allele of the hsf gene (termed hsf4), which encodes the heat shock transcription factor (HSF). At all times in a daily cycle, heat-induced decreases in the levels of PER and TIM were similar in wild-type and hsf4 mutant flies. The results strongly suggest that the heat shock pathway contributes little, if any, to the response of the Drosophila circadian clock to heat signals.