Fig. 1. STAT1–GFP is activated by IFN-γ treatment. (A) U3A cells expressing STAT1–GFP were untreated (a) or treated (b) with IFN-γ for 30 min. STAT1–GFP cellular localization was examined by fluorescent microscopy. (B) U3A cells (lanes 1 and 2) or U3A cells expressing STAT1–GFP (lanes 3 and 4) were untreated or treated with IFN-γ for 30 min. Proteins were immunoprecipitated with anti-STAT1 antibody and western blots performed with anti-STAT1 phosphotyrosine antibody (anti-STAT1 pY) (upper panel) or anti-GFP antibody (lower panel). (C) Nuclear extracts were prepared from U3A cells expressing STAT1–GFP and were untreated or treated for 30 min with IFN-γ. EMSA was performed with the IRF-1 GAS probe. Anti-STAT1 antibody was incubated with extracts prior to addition of probe.