FIG. 4.

Functional nonequivalence of the Stat4 and Stat1 N domains. (Left panels) Uninfected U3A cells (uninfected) or U3A cells expressing murine Stat1 (mStat1), the N4-C1 chimeric Stat protein (N4-C1), or wild-type Stat4 (mStat4) as described in the legend to Fig. 3 were either left untreated (light lines) or were treated with IFN-α (bold lines) for 48 h. (Right panels) Cells were left untreated (light lines) or treated with IFN-γ (bold lines) for 48 h. Results were analyzed by flow cytometry with a Becton Dickinson FACScan for surface expression of MHC class I by using a PE-conjugated anti-class I-specific antibody, clone Tu149 (Caltag).