Analysis of URSG-mediated glucose repression of the GAL1 promoter of Saccharomyces cerevisiae.

Repression of GAL1 expression during growth on glucose is mediated in part by cis-acting promoter elements designated URSG. We show that oligonucleotides containing sequences from two regions of URSG confer glucose repression upon a heterologous promoter. Repression caused by URSG is dependent on trans-acting factors of the glucose repression pathway and is independent of orientation or location within a promoter, suggesting that URSG contains binding sites for a glucose-activated repressor protein(s). Genetic analysis identified three apparently novel genes (URR1, URR3 and URR4) that are specifically required for URSG-mediated repression and may encode such repressor proteins. Mutations in the URR genes suppress the defect in URSG derepression caused by a snf1 mutation.