IFITM3 and influenza: Owing to the observations that IFITM3 is required for an effective IFNβ-mediated anti-influenza response (33), that palmitoylation of IFITM3 is required for its antiviral activity (33), and that FASN is required for Alk-4–mediated IFITM3 palmitoylation (Fig. 2G), we sought to determine the effect of FASN expression on IFNβ-mediated inhibition of influenza virus infection.