Human HSP70 promoter contains at least two distinct regulatory domains

Abstract

The expression of the human HSP70 gene is induced by a wide range of physiological stresses, including exposure to heat shock and heavy metals, or under nonstress conditions, such as in response to serum stimulation. We have previously demonstrated that in either case the regulated expression is at the primary level of transcription. To determine whether transcription is mediated through a single or multiple genetic elements, we have dissected the sequences upstream of the transcription start site of the human HSP70 gene by constructing chimeric genes retaining variable amounts of 5' flanking regions fused to the bacterial gene encoding chloramphenicol acetyltransferase. Transcription from the chimeric genes was determined by S1 nuclease analysis of separate stable transfectants. The sequences required for heat shock and cadmium induction lie between -107 and -68. Within this region is the sequence CTGGAATATTCCCG, which is identical in 12/14 positions with the heat shock element of Drosophila heat shock genes, and a separate sequence, CGNCCCGG, which is homologous to the core of the human metallothionein II metal-responsive element. The sequences required for serum-stimulated transcription are distinct from the heat shock element. The sequence CCAAT at -68 is required for high levels of correctly initiated transcripts, and a purine-rich sequence, GAAGGGAAAAG, at -58 is required for serum stimulation. The human HSP70 promoter contains at least two regulatory domains--a distal domain responsive to heat shock or cadmium and a proximal domain responsive to stimulation by serum.