FIG. 3.

Increased tyrosine phosphorylation of Stat1,2 and Jak1 by IFNs in Shp-2^−/− cells. Serum-starved wild-type and Shp-2^−/− cells were treated with 100 ng of IFN-γ/ml (A) or 1,000 U of IFN-α/ml (B and C) for the indicated time periods. Whole cell extracts (A and B) or anti-Stat2 immunoprecipitates (C) were subjected to SDS-polyacrylamide gel electrophoresis and subsequently to immunoblot analyses with anti-PY, anti-PY-Stat1, anti-Stat1, or anti-Stat2 antibodies as indicated. (D) Serum-starved wild-type and Shp-2^−/− cells were treated with 100 ng of IFN-γ/ml for the indicated time periods. Whole cell extracts were immunoprecipitated with anti-Jak1 antibody and subjected to immunoblot analyses with anti-PY and anti-Jak1 antibodies as indicated.