The yeast Saccharomyces cerevisiae transcription factor Yap1 mediates an adaptive response to oxidative stress by regulating protective genes. H(2)O(2) 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. H(2)O(2) 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 H(2)O(2). 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 H(2)O(2) 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, H(2)O(2), NEM, or acrolein. Sixty-five unique H(2)O(2) 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 H(2)O(2)-responsive subset and YDR042C in the NEM- and acrolein-responsive subset. These findings demonstrate that the distinct mechanisms of Yap1 activation by H(2)O(2) or thiol-reactive chemicals result in selective expression of protective genes.

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