Fig. 7. A model for DIF-1 and stress-induced activation of STATc. The model proposes regulation of STATc at the level of de-phosphorylation. In untreated cells, PTP3 activity is relatively high and STATc is, therefore, minimally tyrosine phosphorylated. Upon stress or DIF-1 treatment, PTP3 is serine-threonine phosphorylated. This reduces PTP3 activity and the level of tyrosine phosphorylation of STATc increases.