FIGURE 6.

SV-elicited phosphorylation of Ser³⁹⁶ and Ser³⁸⁶. A–D, HEK293 cells were transfected with the indicated IRF3 wild type (WT) or mutants and infected or not with SV for 12 h. Lysates were prepared, and phosphorylation of Ser³⁹⁶ was examined by immunoblotting with an antibody recognizing phosphorylated Ser³⁹⁶. Membranes were reprobed with anti-FLAG. Band intensities were quantified using the Kodak image analysis software. Intensities of phosphorylated Ser³⁹⁶ were normalized to intensities of FLAG-tagged IRF3 or IRF3 mutants and expressed as fold increase relative to medium-treated cells transfected with wtIRF3 (lower panels; A and B). E, lysates were prepared from SV-infected HEK293 cells and separated by native PAGE or SDS-PAGE prior to immunoblotting (IB) with anti-Ser(P)³⁸⁶, anti-Ser(P)³⁹⁶, or total IRF3.