Figure 7.

During incubation at 42°C, class II mutant cells synthesize SSA4 mRNA that accumulates in the nucleus. (A) Quantitative analysis of SSA4 mRNA expression and localization. Indicated strains were grown in a selective medium at 22°C until midlog. Cultures were then divided into three samples. One was maintained at 22°C, and the others were shifted to 42°C for the indicated time. Cells were then harvested and the level of SSA4 mRNA and its localization was detected by in situ hybridization technique as described in MATERIALS AND METHODS. After taking pictures of a fluorescent microscope, cells were classified into those where SSA4 mRNA was detected in the cytoplasm, in the nucleus, or not detected at all. The code for the different expression and localization classes is depicted at the bottom right side of panel A. (B) Images of selected samples of cells that were visualized either before (22°C panels) or 15 min after a temperature shiftup (42°C panels), as described in Figure 1.