A deletion of the 3' end of the Drosophila melanogaster hsp70 gene increases stability of mutant mRNA during recovery from heat shock.

hsp40, an X-ray-induced deletion mutant of the major Drosophila melanogaster heat shock protein gene hsp70, was shown to be incorrectly regulated at the translational level. hsp40 protein synthesis persisted at a high level after the release from heat shock, whereas hsp70 protein production was rapidly repressed. This result was observed both in flies heterozygous for the hsp40 gene and in tissue culture cells transfected with the truncated gene. Analysis of the transcription of the hsp40 gene indicated that its mRNA, unlike hsp70 mRNA, was not actively destabilized after a return to control temperatures, permitting prolonged production of the mutant protein.