Transcriptional repressor, activator; role in adjustment to osmotic stress including modulation of mating efficiency; involved in repression of hypoxic genes by Rox1p, repression of several DAN/TIR genes during aerobic growth, ergosterol biosynthetic genes in response to hyperosmotic stress; contributes to recruitment of Tup1p-Cyc8p general repressor to promoters; relocalizes to cytosol under hypoxia; ethanol stress increases the frequency of [MOT3+] formation, while hypoxia eliminates [MOT3+]