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. 2010 Apr;9(4):480–485. doi: 10.1128/EC.00333-09

Fig. 1.

Fig. 1.

Regulation of Ste12p activity in S. cerevisiae. In response to pheromone, the Fus3 MAPK pathway (Ste11-Ste7-Fus3) relays a phosphorylation signal to reach the Dig1p/2p complex, leading to dissociation and Ste12p phosphorylation. Ste12p homodimerization allows the transcription of mating genes containing PRE sequences. Stimulation by the mating pheromone promotes the SUMOylation of Ste12p. In the case of prolonged pheromone treatment, Ste12p is subjected to degradation through a proteasome-mediated mechanism. Upon phosphorylation by Fus3p, Tec1p is rapidly degraded via a ubiquitin-mediated mechanism (SCF Ub. Ligase). In response to filamentation signals, a phosphorylation cascade is transduced via the Kss1 MAPK pathway (Ste11p-Ste7p-Kss1p), leading to the phosphorylation of Ste12p and the dissociation of the Dig1p/2p complex from FRE sequences. The dimerization of phosphorylated Ste12p with Tec1p allows the transcription of filamentation responsive genes. P, phosphorylation; S, SUMOylation; U, ubiquitination.