HEAT-STRESS REGULATES THE HUMAN 70-KDA HEAT-SHOCK GENE THROUGH THE 3'-UNTRANSLATED REGION

Cells respond to a variety of stresses by synthesizing a family of pro teins termed heat-shock proteins (HSP). Recently, the 3'-untranslated regions (UTRs) of some mRNAs have been shown to be important in the po sttranscriptional regulation of protein production. Therefore, we hypo thesized that heat could regulate HSP70 production through the HSP70 3 '-UTR, in addition to its known effects on transcription. To test this hypothesis, cells were transfected with either a plasmid containing s equences encoding the human HSP70 or beta-globin 3'-untranslated regio n placed downstream of a chloramphenicol acetyltransferase (CAT) repor ter gene. In both plasmids, the CAT gene was driven by an SV40 promote r. Following heat stress, cells transfected with the CAT construct con taining the HSP70 3'-UTR showed increased CAT activity relative to the beta-globin 3'-UTR construct. This effect paralleled increases in HSP 70 mRNA and levels of the inducible HSP70 protein by Western blot. The se studies identify a heat-induced mechanism of posttranscriptional co ntrol of HSP70 synthesis utilizing the HSP70 3'-UTR, which may be impo rtant in the cells ability to regulate the heat-shock response.