POTENTIAL INVOLVEMENT OF A CONSTITUTIVE HEAT-SHOCK ELEMENT-BINDING FACTOR IN THE REGULATION OF CHEMICAL STRESS-INDUCED HSP70 GENE-EXPRESSION

It was reported that chemical stresses such as arsenite, cadmium or sa licylate fail to induce synthesis of the inducible form of HSP70 (HSP7 0i). We report here that exposure of cells to higher doses of these ch emical treatments induced significant synthesis of HSP70i in CHO cells as well as other cell lines. The synthesis of HSP70i is primarily reg ulated at the transcriptional level. Although all tested chemical trea tments induced heat shock factor (HSF) binding to the heat shock eleme nt (HSE), HSP70i synthesis appears to be regulated by an alternative f actor (CHEF) which constitutively binds to the HSE at 37 degrees C. Th e treatments, which dissociate the HSE-CHBF complex, induced significa nt HSP70i synthesis. The treatments, which failed to induce HSP70i syn thesis, still activated HSF binding to HSE but the HSE-CHBF complex re mained as that of untreated control cells.