Figure 4.

Skn7 is required for the induction of heat shock gene expression specifically in response to hydrogen peroxide. (A) Northern blot analysis of the effect of skn7Δ mutations on heat shock gene induction by oxidative stress. Total RNA was prepared from midlog-phase cultures of W303-1a and W303-1a skn7Δ grown at 30°C in YPD. Samples for RNA extraction were taken before (time 0) and at the times indicated after the addition of 0.6 mM t-butyl hydrogen peroxide. Northern blots were prepared as described (see MATERIALS AND METHODS) and hybridized to probes specific for HSP12, HSP26, and HSP104. (B) Skn7 is not required for the heat shock induction of heat shock gene expression. W303-1a and skn7Δ cells were grown to midlog phase at 25°C, and a portion of the culture was transferred to a 39°C water bath. Cells were harvested at the times indicated, and RNA was extracted for Northern hybridization with the probes specified in A. Quantitation of mRNA was by PhosphorImager analysis (Molecular Dynamics, Sunnyvale, CA) and was expressed relative to the ACT1 transcript, the abundance of which appeared to be unaffected by oxidative stress.