Regulatory transcription factor IRF-3 plays a critical role in the regulation of innate immune responses, especially production of IFN-α/β, against viral and bacterial infections. IRF-3 is ubiquitously expressed in its inactive form in the cytoplasm. Viral infection induces phosphorylation of the Ser 386 in IRF-3 by IRF-3 kinase (IKK-i/ε, TBK-1). This phosphorylation induces dimerization of IRF-3 and association with the coactivators CBP/p300, and the complex activates the target genes in the nucleus.