Analyses of virus-induced homomeric and heteromeric protein associations between IRF-3 and coactivator CBP/p300.
Cellular genes including the type I interferon genes are activated in response to viral infection. We previously reported that IRF-3 (interferon regulatory factor 3) is specifically phosphorylated on serine residues and directly transmits a virus-induced signal from the cytoplasm to the nucleus, and then participates in the primary phase of gene induction. In this study, we analyzed the molecular mechanism of IRF-3 activation further. The formation of a stable homomeric complex of IRF-3 between the specifically phosphorylated IRF-3 molecules occurred. While virus-induced IRF-7 did not bind to p300, the phosphorylated IRF-3 complex formed a stable multimeric complex with p300 (active holocomplex). Competition using a synthetic phosphopeptide corresponding to the activated IRF-3 demonstrated that p300 directly recognizes the structure in the vicinity of the phosphorylated residues of IRF-3. These results indicated that the phosphorylation of serine residues at positions 385 and 386 is critical for the formation of the holocomplex, presumably through a conformational switch facilitating homodimer formation and the generation of the interaction interface with CBP/p300.
Suhara
W
W
Department of Tumor Cell Biology, The Tokyo Metropolitan Institute of Medical Science, Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan.
Yoneyama
M
M
Iwamura
T
T
Yoshimura
S
S
Tamura
K
K
Namiki
H
H
Aimoto
S
S
Fujita
T
T
D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D050881:E1A-Associated p300 Protein; D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; D051379:Mice; D009522:Newcastle disease virus / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism*; D010748:Phosphopeptides / Q000378:metabolism; D010766:Phosphorylation; D017354:Point Mutation; D011233:Precipitin Tests; D012694:Serine / Q000235:genetics; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; C494233:Irf3 protein, mouse; C494235:Irf7 protein, mouse; D009687:Nuclear Proteins; D010748:Phosphopeptides; D015534:Trans-Activators; D014157:Transcription Factors; D012694:Serine; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse