In vitro synthesis of heat-shock proteins by mRNAs from chicken embryo fibroblasts.

The pattern of proteins synthesized by chicken embryo fibroblasts changes dramatically after these cells are incubated at 45 degrees C for a few hours. Three proteins (Mr = 22,000, 76,000, and 95,000) account for almost 50% of the cell's protein synthetic capacity immediately after the heat-shock (Kelley, P.M., and Schlesinger, M.J. (1978) Cell 15, 1277-1286). When mRNAs were isolated from heat-shocked cells and translated in a cell-free protein synthesizing system, a pattern of proteins virtually identical with that made by intact heat-shocked cells was detected. Mobilities in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and radioimmune precipitation with specific antisera were used to establish the identity of in vitro- and in vivo-generated heat-shock proteins. The mRNAs coding for the major heat-shock proteins could be separated by rate zonal centrifugation in a sucrose gradient and mRNAs with sedimentation coefficients of 20 S, 18 S, and 13 S were translated in vitro to yield proteins of 95, 76, and 22 kilodaltons, respectively.