CLONING AND CHARACTERIZATION OF THE PROMOTER FOR MURINE 84-KDA HEAT-SHOCK PROTEIN

The 90-kDa heat-shock (HS) proteins (HSP90) are members of the HSP fam ily. Their synthesis is inducible by HS and a variety of stress signal s. HSP90 is also abundant under normal physiological conditions and it s synthesis can be regulated during growth and differentiation. Theref ore, HSP90 is speculated to have important biological functions, in ad dition to its role in mediating stress responses. However, the mechani sm(s) regulating hsp90 gene expression in nonstressed cells is poorly understood. As a prerequisite towards understanding the basis for hsp9 0 regulation, we have cloned and characterized the 5' flanking region of murine hsp84, one of two genes which code for HSP90 proteins. Full basal promoter activity of hsp84 was found to be associated with a 627 -bp region immediately upstream from the transcription start point (ts p). Sequence analysis revealed several putative regulatory elements, i ncluding a HS element (HSE), an AP1-binding site (AP1), a cyclic AMP r esponse element (CRE), and four stimulatory protein-1-binding sites (S P1). HS inducibility required the HSE which was bound by HS transcript ion factor-1 (HSF-l) present in extracts prepared from cells exposed t o HS. The HSE was not required for basal (non-HS) expression, but, int erestingly, two protein-HSE complexes, devoid of HSF-1 and HSF-2, were formed under these conditions. The potential significance of these fi ndings to the expression of hsp84 under normal physiological condition s is discussed.