FIG. 3.

Activation of Ras inhibits phosphorylation of STAT1 and STAT2 induced by IFN-α. (A) Vector control cells (Cont) and RasV12 cells were stimulated with IFN-α (500 U/ml) for 0, 0.5, 1, and 2 h. Western blot analysis for phosphorylated STAT1 (p-STAT1), total STAT1 (t-STAT1), phosphorylated STAT2 (p-STAT2), total STAT2 (t-STAT2), and total ERK (t-ERK) was performed. Representative images of three independent experiments are shown. (B) The total and phosphorylated amounts of STAT1 and STAT2 were quantified by densitometry analysis. The density ratios of t-STAT1, p-STAT1, t-STAT2, and p-STAT2 to t-ERK are shown as percentages normalized to values for vector control cells stimulated with IFN-α for 0.5 h. The results are means ± standard errors of the means (SEM) from three independent experiments. *, P < 0.05 by one-way ANOVA. (C) Decreasing amounts of total protein were analyzed by Western blot analysis for levels of t-STAT1 and t-STAT2 and for actin (as a loading control). (D) The total amounts of STAT1 and STAT2 were quantified by densitometry analysis. The levels of t-STAT1 and t-STAT2 were normalized to that for actin, and the relative amount of STAT protein in RasV12 compared to that of control cells is depicted graphically. The results are means ± SEM from three independent experiments. N/A, not applicable; *, P < 0.05 by one-way ANOVA. (E) Activation of Ras does not inhibit phosphorylation of STAT1 induced by IFN-γ. Vector control cells (Cont) and RasV12 cells were stimulated with IFN-γ (50 ng/ml) for 0.5 h. The density ratios of phosphorylated STAT1 (p-STAT1/t-ERK) and total STAT1 (t-STAT1/t-ERK) to total ERK are shown as percentages normalized to values for vector control cells stimulated with IFN-γ.