Abstract
Expression of the STA1 gene, encoding an extracellular glucoamylase, is regulated positively by GAM1 or negatively by INH1 and heterozygosity at MAT (mating-type locus). From the analysis of diploid cells carrying mat mutations, we showed that different sets of mating-type genes were required for the repression of STA1 depending on both the copy number of STA1 and culture conditions. A multi-copy plasmid carrying STA1 relieved the MAT repression but did not affect glucoamylase production from INH1 or garni cells. RNA blot, SI mapping, and immunoprecipitation analyses revealed that GAM1 was required for the transcription of STA1 and that INH1 and heterozygosity at MAT exerted their functions at both transcriptional and post-transcriptional levels depending on culture conditions.
