IFIT3 (IFN-induced protein with tetratricopeptide repeats 3), also known as IFIT-4, ISG-60 or RIG-G, is a 56 kDa IFN induced protein. IFIT3 has been identified to be associated with strong IFN antiviral activity. Upon RNA virus infection, IFIT3 is significantly induced, ectopic expression or knockdown of IFIT3 could, respectively, enhance or impair IFN regulatory factor 3 (IRF3)-mediated gene expression. IFIT3 thus may serve as an important modulator in innate immunity, revealing a new function of the IFIT family proteins.