The yeast transcriptional activator Gal4 localizes to UAS(GAL) sites even in the absence of galactose but cannot activate transcription due to an association with the Gal80 protein. By 4 min after galactose addition, Gal4-activated gene transcription ensues. It is well established that this rapid induction arises through a galactose-triggered association between the Gal80 and Gal3 proteins that decreases the association of Gal80 and Gal4.