Human IRF3 is activated through a two step phosphorylation in the C-terminal domain mediated by TBK1 and/or IKKi. It requires Ser386 and/or Ser385 (site 1) and a cluster of serine/threonine residues between Ser396 and Ser405 (site 2) (Panne et al. 2007). Phosphorylated residues at site 2 alleviate autoinhibition to allow interaction with CBP (CREB-binding protein) and facilitate phosphorylation at site 1. Phosphorylation at site 1 is required for IRF3 dimerization.
IRF3 and IRF7 transcription factors possess distinct structural characteristics; IRF7 is phosphorylated on Ser477 and Ser479 residues (Lin R et al. 2000). TRAF6 mediated ubiquitination of IRF7 is also required and essential for IRF7 phosphorylation and activation. The K-63 linked ubiquitination occurs on the last three C-terminal lysine sites (positions 444, 446, and 452) of human IRF7 independently of its C-terminal functional phosphorylation sites.(Ning et al. 2008).
Panne, D, McWhirter, SM, Maniatis, T, Harrison, SC
Fitzgerald, KA, McWhirter, SM, Faia, KL, Rowe, DC, Latz, E, Golenbock, DT, Coyle, AJ, Liao, SM, Maniatis, T
Mori, M, Yoneyama, M, Ito, T, Takahashi, K, Inagaki, F, Fujita, T
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