Yap1 activation by H2O2 or thiol-reactive chemicals elicits distinct adaptive gene responses

The yeast Saccharomyces cerevisiae transcription factor Yap1 mediates an adaptive response to oxidative stress by regulating protective genes. H2O2 activates Yap1 through the Gpx3-mediated formation of a Yap1 Cys303-Cys598 intramolecular disulfide bond. Thiol-reactive electrophiles can activate Yap1 directly by adduction to cysteine residues in the C-terminal domain containing Cys598, Cys620, and Cys629. H2O2 and N-ethylmaleimide (NEM) showed no cross-protection against each other, whereas another thiol-reactive chemical, acrolein, elicited Yap1-dependent cross-protection against NEM, but not H2O2. Either Cys620 or Cys629 was sufficient for activation of Yap1 by NEM or acrolein; Cys598 was dispensable for this activation mechanism. To determine whether Yap1 activated by H2O2 or thiol-reactive chemicals elicits distinct adaptive gene responses, microarray analysis was performed on the wild-type strain or its isogenic single-deletion strain Δyap1 treated with control buffer, H2O2, NEM, or acrolein. Sixty-five unique H2O2 and 327 NEM and acrolein Yap1-dependent responsive genes were identified. Functional analysis using single-gene-deletion yeast strains demonstrated that protection was conferred by CTA1 and CTT1 in the H2O2-responsive subset and YDR042C in the NEM- and acrolein-responsive subset. These findings demonstrate that the distinct mechanisms of Yap1 activation by H2O2 or thiol-reactive chemicals result in selective expression of protective genes.