title: Interferon regulatory factor 3 is regulated by a dual phosphorylation-dependent switch.
abstract: The transcription factor interferon regulatory factor 3 (IRF-3) regulates genes in the innate immune response. IRF-3 is activated through phosphorylation by the kinases IKK epsilon and/or TBK1. Phosphorylation results in IRF-3 dimerization and removal of an autoinhibitory structure to allow interaction with the coactivators CBP/p300. The precise role of the different phosphorylation sites has remained controversial. Using purified proteins we show that TBK1 can directly phosphorylate full-length IRF-3 in vitro. Phosphorylation at residues in site 2 (Ser(396)-Ser(405)) alleviates autoinhibition to allow interaction with CBP (CREB-binding protein) and facilitates phosphorylation at site 1 (Ser(385) or Ser(386)). Phosphorylation at site 1 is, in turn, required for IRF-3 dimerization. The data support a two-step phosphorylation model for IRF-3 activation mediated by TBK1.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Panne
authors.forename: Sarah M
authors.initials: SM
authors.lastname: McWhirter
authors.forename: Tom
authors.initials: T
authors.lastname: Maniatis
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Harrison
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000378:metabolism; D001665:Binding Sites; D002460:Cell Line; D019281:Dimerization; D006801:Humans; D006860:Hydrogen Bonding; D007313:Insecta; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D050838:Interferon Regulatory Factor-3; D010455:Peptides; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human