Mutational analysis of Yap1 protein, an AP-1-like transcriptional activator of Saccharomyces cerevisiae.

To define the essential amino acid residues of Yap1 in stress response, we generated yap1 mutations by in vitro mutagenesis, which cause defects in mediating resistance to the stress of H2O2, but not of CdCl2. Sequence analysis of the mutant yap1 genes revealed three point mutations and two truncation mutations near the carboxy-terminus. The truncation mutations resulted in hyperresistance to cadmium. Northern blot analysis of stress-induced levels of TRX2 and GSH1 mRNAs indicated that the ability of the mutant Yap1 protein to induce transcriptional activation of target genes correlates well with its ability to confer stress resistance. The carboxy-terminal domain of Yap1 appears to act negatively in cadmium resistance.