Figure 5.

Phosphorylation on Tyr-701 of Stat1 is required for PIAS1–Stat1 interaction. U3A cells complemented with Stat1 or Stat1(Tyr-701 → Phe) mutant protein were untreated or treated with IFN-γ for 15 min, and protein extracts were prepared. (A) Immunoprecipitation was performed with anti-Stat1 followed by blotting with a specific phosphotyrosine antiserum [anti-pTyr (Transduction Laboratories, Lexington, KY)]. The same filter was washed and reprobed with anti-Stat1 (Lower). (B) Immunoprecipitation was performed with anti-PIAS1n antiserum and blotted with anti-Stat1. The filter was washed and reprobed with anti-PIAS1 (Lower).