Identification of a novel in vivo virus-targeted phosphorylation site in interferon regulatory factor-3 (IRF3).
The transcription factor interferon regulatory factor-3 (IRF3) regulates expression of type I interferon-beta and plays an important role in antiviral immunity. Despite the biological importance of IRF3, its in vivo phosphorylation pattern has not been reported. In this study, we have identified residues in IRF3 that are phosphorylated in vivo after infection with Sendai virus. We found that Sendai virus induced phosphorylation of the C-terminal residues Thr(390) and Ser(396), in addition to either Ser(385) or Ser(386). Moreover, Ser(173) and Ser(175) were constitutively phosphorylated. Ser(396) has previously been suggested to be the major target of the IRF3-activating kinase TBK1 (TANK-binding kinase-1), whereas Thr(390) has not previously been implicated in IRF3 regulation. Mutagenesis studies indicated that phosphorylation of Thr(390) promotes Ser(396) phosphorylation and binding to the coactivator cAMP-response element-binding protein. Taken together, our results show that IRF3 is subject to multiple interdependent phosphorylations, and we identify Thr(390) as a novel in vivo phosphorylation site that modulates the phosphorylation status of TBK1-targeted Ser(396).
Bergstroem
Bjarte
B
Department of Laboratory Medicine, Children's and Women's Health, Faculty of Medicine, orwegian University of Science and Technology, 7006 Trondheim, Norway.
Johnsen
Ingvild B
IB
Nguyen
Thuy Thanh
TT
Hagen
Lars
L
Slupphaug
Geir
G
Thommesen
Liv
L
Anthonsen
Marit W
MW
D000595:Amino Acid Sequence; D001665:Binding Sites; D015967:Gene Expression Regulation, Viral; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D029082:Sendai virus / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D013912:Threonine / Q000737:chemistry
C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D011994:Recombinant Proteins; D013912:Threonine; D012694:Serine; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human