FIG. 2.

Kinetics of STAT activation by IFN-α or IFN-γ. Serum-starved wild-type and Shp-2^−/− cells were treated with 1,000 U of IFN-α/ml (A) or 100 ng/ml IFN-γ (B) for the indicated time periods. Nuclear extracts were prepared for detection of STAT activity by EMSA with ³²P-labeled hSIE probe. The arrows denote the specific STATs-DNA complexes. In supershift assays (SS) shown in panels A and B, anti-Stat1 or anti-Stat2 antibodies were added to the reaction mixture before incubation with the DNA probe.