Induction of IRF-3/-7 kinase and NF-kappaB in response to double-stranded RNA and virus infection: common and unique pathways.
BACKGROUND
Infection by virus or treatment with double-stranded RNA (dsRNA) results in the activation of transcription factors including IRF-3, IRF-7 and a pleiotropic regulator NF-kappaB by specific phosphorylation. These factors are important in triggering a cascade of antiviral responses. A protein kinase that is yet to be identified is responsible for the activation of these factors and plays a key role in the responses.


RESULTS
The signal cascade was analysed using sensitive assays for the activation of IRF-3 and NF-kappaB, and various inhibitors. We found that the activation of IRF-3 and NF-kappaB by dsRNA or virus involves a process that is sensitive to Geldanamycin. Although the induction of NF-kappaB by dsRNA/virus and TNF-alpha involves common downstream pathways including IKK activation, the upstream, Geldanamycin-sensitive process was unique to the dsRNA/virus-induced signal. By an in vitro assay using cell extract, we found an inducible protein kinase activity with physiological specificity of IRF-3 phosphorylation. Furthermore, the same extract specifically phosphorylated IRF-7 in a similar manner.


CONCLUSIONS
Double-stranded RNA or virus triggers a specific signal cascade that results in the activation of the IRF-3/-7 kinase we detected, which corresponds to the long-sought signalling machinery that is responsible for triggering the early phase of innate response. The signal branches to a common NF-kappaB activation cascade, thus resulting in the activation of a set of critical transcription factors for the response.
Iwamura
T
T
Department of Tumor Cell Biology, The Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan.
Yoneyama
M
M
Yamaguchi
K
K
Suhara
W
W
Mori
W
W
Shiota
K
K
Okabe
Y
Y
Namiki
H
H
Fujita
T
T
D016227:Benzoquinones; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction; D004797:Enzyme-Linked Immunosorbent Assay; D015971:Gene Expression Regulation, Enzymologic; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; D047029:Lactams, Macrocyclic; D016328:NF-kappa B / Q000096:biosynthesis*; D009522:Newcastle disease virus / Q000378:metabolism*; D010766:Phosphorylation; D011070:Poly I-C / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D012330:RNA, Double-Stranded / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016227:Benzoquinones; D004268:DNA-Binding Proteins; C494232:IRF3 protein, human; C494234:IRF7 protein, human; D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; D047029:Lactams, Macrocyclic; D016328:NF-kappa B; D011809:Quinones; D012330:RNA, Double-Stranded; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D014108:Tosylphenylalanyl Chloromethyl Ketone; D017346:Protein Serine-Threonine Kinases; D011070:Poly I-C; C001277:geldanamycin