Enhancement of Glucocorticoid Receptor-Mediated Gene Expression by Constitutively Active Heat Shock Factor 1

To further define the role of heat shock factor 1 (HSF1) in the stress potentiation of glucocorticoid receptor (GR) activity, we placed a constitutively active mutant of human HSF1 (hHSF1-E189) under the control of a doxycycline (DOX)-inducible vec-tor. In mouse L929 cells, DOX-induced expression of hHSF1-E189 correlated with in vivo occupancy of the human heat shock protein 70 (hHsp70) pro-moter (chromatin-immunoprecipitation assay) and with increased activity under nonstress conditions at the hHsp70 promoter controlling expression of chloramphenicol acetyl transferase (CAT) (p2500-CAT). Comparison of hHSF1-E189 against stress-activated, endogenous HSF1 for DNA-binding, p2500-CAT, and Hsp70 protein expression activi