A MULTICOPY SUPPRESSOR GENE, MSS10, RESTORES STA2 EXPRESSION IN SACCHAROMYCES-CEREVISIAE STRAINS CONTAINING THE STA10 REPRESSOR GENE

Transcription of the three unlinked, homologous STA1-3 glucoamylase-en coding genes, involved in starch degradation by Saccharomyces cerevisi ae, was previously shown to be down-regulated by the presence of STA10 , acting via three upstream repression sequence regions that were iden tified in the STAZ promoter. Here we report the cloning and characteri zation of a putative transcriptional activator gene, MSS10 (multicopy suppressor of STA10), which, when present in multiple copies, overcome s STA10 repression. Deletion of MSS10, located on chromosome XV, resul ted in media-specific extinction of glucoamylase synthesis. The nucleo tide sequence of MSS10 is identical to three other genes from S. cerev isiae identified as: FUP1, a gene that enhances iron-limited growth; P HD2, a gene identified for its ability to induce pseudohyphal growth i n diploid cells grown on nitrogen-limited media; and MSN1, a gene enco ding a transcriptional activator involved in invertase regulation.