Key transcription factor for sexual development. Activates the transcription of the matp, matm, mei2, mfm, ste6 and rgs1 genes. Binds specifically to a DNA fragment carrying a 10-base motif 5'-TTCTTTGTTY-3'. Accumulates in the nucleus under conditions of nitrogen starvation and in the presence of mating pheromones. By nitrogen starvation. Phosphorylation results in inactivation.