Purified human factor activates heat shock promoter in a HeLa cell-free transcription system.

Heat shock protein (hsp) genes are typically silent and are activated by various stresses including heat. As a first step toward understanding this activation event, a human factor, referred to here as human heat shock transcription factor (human HTF), has been purified approximately 14,000-fold from extracts of heat-treated HeLa cells by means of sequence-specific DNA affinity chromatography. The most highly purified fraction of human HTF binds specifically to the known regulatory sequence element (HSE) of hsp genes as shown by footprinting experiments. Purified human HTF has an apparent molecular mass of 83 kDa. Human HTF is specifically required for activation of an hsp gene promoter in a reconstituted in vitro transcription system from human cells. Activation is dependent on the presence of the HSEs in the transcription template.