Fig. 3. Analysis of the effects of PTP inhibition on STATc tyrosine phosphorylation. (A) Induction assay using dominant-negative forms of PTP3 cells transformed with myc:PTP3CS were starved in suspension for 4 hours and then exposed to DIF-1 at 100 nM. The activation of STATc was analysed by western transfer using an antibody specific to the tyrosine phosphorylated form of STATc. As a loading control, a parallel blot was probed with a non phospho-specific STATc antibody. (B) Pervanadate-mediated inhibition of PTP3 Ax-2 cells. Cells were starved in suspension for 4 hours, then exposed to DIF-1 at 100 nM or pervanadate at 2 mM (1 mM H₂O₂ and 2 mM NaVO₄) for the indicated times and analysed as in A.