Maximal Stress-Induced Transcription from the Human HSP70 Promoter Requires Interactions with the Basal Promoter Elements Independent of Rotational Alignment

Transcription of the human HSP70 gene is regulated by a complex array of cis-acting promoter elements that respond to conditions that include normal conditions of cell growth and induction following physiological stress. We have examined the requirements of the basal and inducible promoter elements by using promoter mutations and a transient transfection assay. Multiple forms of stress-induced transcription, including heat shock and incubation with heavy metals or amino acid analogs, are mediated by a single heat shock element (HSE) between -105 and -91 consisting of three contiguous 5-base-pair units, NGAAN, that are inverted relative to adjacent units. Maximal inducible expression requires a fully functional basal promoter. Spacing mutations which alter the relative helical orientation of adjacent genetic elements have only minimal effects on basal and stress-inducible expression and show no effects of periodicity. In addition, placement of the HSE adjacent to the basal promoter removes the requirements for a fully functional basal promoter for maximal stress-inducible expression. These results suggest that factors bound at the HSE and the basal promoter can function through multiple interactions.