A NOVEL MUTATION OCCURRING IN THE PHO80 GENE SUPPRESSES THE PHO4C MUTATIONS OF SACCHAROMYCES-CEREVISIAE

We have isolated suppressors of a PHO4c (a positive regulator) mutant which normally confers weak constitutivity for acid phosphatase production on the Saccharomyces cell. One dominant suppressor (PHO80-2) was found to be an allele of PHO80 (a negative regulator) that changes G to A, resulting in substitution of isoleucine for methionine 42 of the Pho80 protein. Substitution of valine (PHO80-3) or leucine (PHO80-4) for the same methionine by site-directed mutagenesis also suppressed PHO(c). Suppression by PHO80-2) did show some allele specificity. From these results we were able to delimit the region of PHO80 which may interact with the Pho4 protein.