Expression and purification of human heat-shock transcription factor 1

Heat-shock factor 1 (HSF1) is a 57-kDa cytoplasmic protein which binds to the promoters of heat-shock genes and activates transcription during heat shock. We describe here the expression and purification of the 529 amino acids form of human HSF1. We designed a new and complete purification protocol involving ammonium sulfate precipitation, heparin-Sepharose affinity, and ion-exchange chromatography, which allows the purification of large amounts of pure and active recombinant protein. HSF1 isolated by this method is pure as that assessed by SDS-PAGE and reverse-phase HPLC. The purified protein is recognized by specific anti-HSF1 antibodies, binds to heat-shock elements, and activates the promoter of the heat-shock protein 70A gene in vitro.