FIG. 8.
Hypersensitivity of HSF1-null mouse embryonic fibroblast cells to high temperatures is restored by ectopic expression of chicken HSF1. (A) Northern blot analysis of heat shock genes in HSF1+/+, HSF1+/−, and HSF1−/− mouse embryonic fibroblast cells before and after heat shock at 43°C for 30 min. (B) Sixteen hours after the HSF1+/+ (open bars) and HSF1−/− (gray bars) mouse embryonic fibroblast cells were plated on culture dishes, the dishes were maintained in an incubator at each indicated temperature. Numbers of attached cells were counted at 9 h after the incubation. Means and standard deviations of three independent experiments are shown. (C) HSF1+/+ (diamonds) and HSF1−/− (squares) mouse embryonic fibroblast cells were incubated at 41.5°C for the indicated periods, and numbers of attached cells were counted. (D) Morphology of MEF cells incubated at 41.5°C under a Axiovert 200 microscope (Zeiss). (E) Mouse embryonic fibroblast cells were incubated in the presence of adenovirus expressing LacZ (Ad-LacZ) or chicken HSF1 (Ad-cHSF1). Western blot analysis of HSF1 was performed with these extracts. The level of endogenous HSF1 in HSF1+/+ mouse embryonic fibroblast cells was too low to be detected. (F) Twenty-four hours after the mouse embryonic fibroblast cells were plated, cells were maintained in the presence or absence of adenovirus (106/ml) for 24 h. Then the cells were incubated at 42°C for the indicated periods. Protein levels of Hsp90, Hsp70, Hsp27, and actin were examined by Western blot analysis with extracts from these cells. (G) Numbers of attached cells were counted at the indicated times after incubation at 42°C. Means and standard deviations of three independent experiments are shown.