OVEREXPRESSION OF YAP2, CODING FOR A NEW YAP PROTEIN, AND YAP1 IN SACCHAROMYCES-CEREVISIAE ALLEVIATES GROWTH-INHIBITION CAUSED BY 1,10-PHENANTHROLINE

A new member of the yeast yAP, designated YAP2, has been isolated and characterized. The protein displays a high homology with the DNA-bindi ng domain of yAP-1, which contains a basic DNA-binding domain and leuc ine zipper motif and binds in vitro to the same cis-element. Growth ar rest of yeast caused by low concentrations of 1,10-phenanthroline, res ulting in zinc and/or iron deprivation, is overcome by overexpression of YAP1 or YAP2. In fact, yeast cells overexpressing YAP1 or YAP2 disp lay pleiotropic-drug resistance. On the other hand, a yap2 null mutant has an increased thermotolerance under starvation conditions caused b y 1,10-phenanthroline. The latter mutant might become an excellent too l in the study of pathways leading toward thermotolerance acquisition.