FIG. 3.

Effects of transcription factor mutations on basal thermotolerance. (A) Basal thermotolerance of wild-type and mutant cells. Cell survival was analyzed as described for Fig. 2A except that cells were directly exposed to 48°C without preconditioning. Values represent the means and standard deviations of the results of at least three experiments. (B) Schematic representation of the thermal treatments. (C) RT-PCR analysis of various mRNAs. Wild-type HSF1 cells (lanes 1 to 7) and hsf1-R206S-H220R cells (lanes 8 to 14) expressing HSP104 were grown in ESD medium lacking uracil and were heat-shocked as shown in panel B. Total RNA prepared from the cells was subjected to RT-PCR analysis. C, control cells. (D) Growth of wild-type and mutant cells after severe heat shock. Wild-type (open circles), hsf1-R206S-H220R (filled circles), and msn2Δ msn4Δ (open squares) cells expressing HSP104 were grown in ESD medium lacking uracil at 28°C. Cell cultures were shifted to 48°C for 6 min and then returned to 28°C. At the indicated times, aliquots of cells were diluted into ESD medium and plated onto YPD medium to determine cell growth. Cell numbers were plotted relative to those of the 28°C incubation at 0 min. Values represent the means and standard deviations of the results of at least three experiments.