Isolation and characterization of the SUD1 gene, which encodes a global repressor of core promoter activity in Saccharomyces cerevisiae.

The SUD1 gene was identified during a hunt for mutants that are able to express an sta1 gene (encoding an extracellular glucoamylase) lacking an upstream activation sequence (UAS) for transcription. A null allele of sud1 alleviated the transcriptional defect of the UAS-less sta1 and also suppressed mutations in trans-acting genes (GAM1/SNF2 and GAM3/ADR6) required for transcription of STA1. The mutation also increased expression from various core promoters (CYC1, CUP1, HIS3, PUT1, and PUT2), suggesting that the SUD1 protein is a global transcriptional regulator that plays a negative role at or near the TATA element. However, the SUD1 function was ineffective on promoters containing a UAS from either STA1 or GAL10 under derepressed conditions. The sud1 mutation suppressed the salt-sensitive cell growth phenotype caused by elevated levels of the TATA-binding protein (SPT15), further suggesting a transcriptional role for SUD1. sud1 cells showed additional pleiotropic phenotypes: temperature-sensitive (ts) growth, reduced efficiencies of sporulation, and sensitivity to heat shock and nitrogen starvation. The SUD1 gene is predicted to encode a 64 kDa, hydrophilic protein.