FIG. 2.

Tyr phosphorylation of Stat3 deletion mutants stimulated with EGF or IL-6. (A) COS-1 cells were transfected with control (C) or Stat3 expression plasmids as labeled and either left untreated or treated with EGF for 15 min. The cell lysates were prepared and subjected to Western blot analysis using antibody against an anti-phospho-Tyr-705-Stat3 (pY₇₀₅ST3), as indicated in the upper panel. The membrane was stripped and reprobed with an anti-Stat3 antibody (lower panel). (B) Transfected HepG2 cells were either left untreated (−) or treated with IL-6 (+) for 15 min. Cell lysates were immunoprecipitated (IP) with FLAG antibody, and the immunoprecipitates were subjected to Western blot analysis using the anti-pY₇₀₅ST3 antibody (upper panel). The blots were stripped and reprobed with Stat3 antibody (lower panel).