High-level, heat-regulated synthesis of proteins in eukaryotic cells

Plasmids have been constructed in which promoters of 70-kDa heat-shock protein genes (hsp70) of human and Drosophila origin were linked to three different eukaryotic genes encoding human growth hormone (hGH), chicken lysozyme (cL) and a human influenza haemagglutinin (HA). Following transfection into widely divergent eukaryotic cells, the hybrid genes direct the transient, heat-regulated synthesis of the three proteins. hGH and cL are secreted into the medium. A human hsp70-hGH construct was used to establish stable mouse fibroblast lines that are capable of producing and secreting hGH at high levels following heat induction: hGH is secreted at a 500-1200-fold higher rate by heat-treated than by untreated cells.