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Crystal structure of mouse phosphorylated IRF-3 bound to CBP
Structural highlights
FunctionIRF3_MOUSE Key transcriptional regulator of type I interferon (IFN)-dependent immune responses which plays a critical role in the innate immune response against DNA and RNA viruses (PubMed:15800576). Regulates the transcription of type I IFN genes (IFN-alpha and IFN-beta) and IFN-stimulated genes (ISG) by binding to an interferon-stimulated response element (ISRE) in their promoters (PubMed:15800576). Acts as a more potent activator of the IFN-beta (IFNB) gene than the IFN-alpha (IFNA) gene and plays a critical role in both the early and late phases of the IFNA/B gene induction (PubMed:16846591, PubMed:16979567, PubMed:20049431). Found in an inactive form in the cytoplasm of uninfected cells and following viral infection, double-stranded RNA (dsRNA), or toll-like receptor (TLR) signaling, is phosphorylated by IKBKE and TBK1 kinases (PubMed:16846591, PubMed:16979567, PubMed:20049431). This induces a conformational change, leading to its dimerization and nuclear localization and association with CREB binding protein (CREBBP) to form dsRNA-activated factor 1 (DRAF1), a complex which activates the transcription of the type I IFN and ISG genes (PubMed:16846591, PubMed:16979567, PubMed:20049431). Can activate distinct gene expression programs in macrophages and can induce significant apoptosis in primary macrophages (PubMed:16846591, PubMed:16979567, PubMed:20049431).[1] [2] [3] [4] Publication Abstract from PubMedThe innate immune system is the first line of defense against bacterial and viral infections. The recognition of pathogen-associated molecular patterns by the RIG-I-like receptors, TLRs, and cGAS leads to the induction of IFN-I by activating the transcription factor IRF-3. Although the mechanism of IRF-3 activation has been extensively studied, the structural basis of IRF-3 activation upon phosphorylation is not fully understood. In this study, we determined the crystal structures of phosphorylated human and mouse IRF-3 bound to CREB-binding protein (CBP), which reveal that phosphorylated IRF-3 forms a dimer via pSer(386) (pSer(379) in mouse IRF-3) and a downstream pLxIS motif. Size-exclusion chromatography and cell-based studies show that mutations of key residues interacting with pSer(386) severely impair IRF-3 activation and IFN-beta induction. By contrast, phosphorylation of Ser(396) within the pLxIS motif of human IRF-3 only plays a moderate role in IRF-3 activation. The mouse IRF-3/CBP complex structure reveals that the mechanism of mouse IRF-3 activation is similar but distinct from human IRF-3. These structural and functional studies reveal the detailed mechanism of IRF-3 activation upon phosphorylation. The Structural Basis of IRF-3 Activation upon Phosphorylation.,Jing T, Zhao B, Xu P, Gao X, Chi L, Han H, Sankaran B, Li P J Immunol. 2020 Aug 21. pii: jimmunol.2000026. doi: 10.4049/jimmunol.2000026. PMID:32826280[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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