IRF3 (S386A, S396A mutant; human, recombinant)

IFR3 (S386A, S396A mutant; human recombinant) contains amino acids corresponding to human IRF3 (Item No. 22811) with alanine substituted for serine at positions 386 and 396. Interferon regulatory factor 3 (IRF3) is a member of the IRF family that plays a crucial role in activation of innate immunity and inflammation in response to viral infection, functioning as a molecular switch for antiviral activity.^1,2,3,4,5 Double-stranded RNA generated during a viral infection leads to IRF3 activation through serine/threonine phosphorylation by TBK1 (Item No. 22817) or IKKε (IKBKE) kinases, which induces a conformational change leading to its dimerization, nuclear localization, and association with CREB binding protein (CREBBP)/p300.^1,2,4,6 The complex formed by this association, known as DRAF1, activates transcription of interferon α (IFN-α) and IFN-β as well as other IFN-induced genes, which play a critical role in the type 1 IFN-dependent immune response.^1,5,6 Various serine residues have been implicated in IRF3 activation, including S386 and S396.⁷ TBK1 and IKKε phosphorylation of IRF3 is decreased when serine is replaced with alanine at positions 396, 398, 402, and 405 and with threonine at position 404. Phosphorylation of S386 is essential for IRF3 oligomerization and binding to p300, and phosphorylation of S396, T390, and either S385 or S386 occurs following Sendai viral infection in HEK293 cells.^8,9

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1. Shu, C., Sankaran, B., Chaton, C.T., et al. Structural insights into the functions of TBK1 in innate antimicrobial immunity. Structure 21(7), 1137-1148 (2013).

2. Huang, J., Liu, T., Xu, L.G., et al. SIKE is an IKKε/TBK1-associated suppressor of TLR3- and virus-triggered IRF-3 activation pathways. EMBO J. 24(23), 4018-4028 (2005).

3. Xu, L.G., Wang, Y.Y., Han, K.J., et al. VISA is an adapter protein required for virus-triggered IFN-β signaling. Mol. Cell. 19(6), 727-740 (2005).

4. tenOever, B.R., Servant, M.J., Grandvaux, N., et al. Recognition of the measles virus nucleocapsid as a mechanism of IRF-3 activation. J. Virol. 76(8), 3659-3669 (2002).

5. Peteranderl, C., and Herold, S. The impact of the interferon/TNF-related apoptosis-inducing ligand signaling axis on disease progression in respiratory viral infection and beyond. Front. Immunol. 8:13, (2017).

6. Gu, L., Fullam, A., Brennan, R., et al. Human DEAD box helicase 3 couples IκB kinase ε to interferon regulatory factor 3 activation. Mol. Cell. Biol. 33(10), 2004-2015 (2013).

7. McWhirter, S.M., Fitzgerald, K.A., Rosains, J., et al. IFN-regulatory factor 3-dependent gene expression is defective in Tbk1-deficient mouse embryonic fibroblasts. PNAS 101(1), 233-238 (2004).

8. Takahasi, K., Horiuchi, M., Fujii, K., et al. Ser³⁸⁶ phosphorylation of transcription factor IRF-3 induces dimerization and association with CBP/p300 without overall conformational change. Genes Cells 15, 901-910 (2010).

9. Bergstroem, B., Johnsen, I.B., Nguyen, T.T., et al. Identification of a novel in vivo virus-targeted phosphorylation site in interferon regulatory factor-2 (IRF3). The Journal of Biological Chemisty 285(32), 24904-24914 (2010).