IFN-regulatory factor 3-dependent gene expression is defective in Tbk1-deficient mouse embryonic fibroblasts
Department of Molecular and Cellular Biology; Department of Medicine, Division of Infectious Diseases and Immunology
Medical Subject Headings
Animals; DNA-Binding Proteins; Fibroblasts; Gene Expression; I-kappa B Kinase; Interferon Regulatory Factor-3; Interferon-beta; Mice; Mice, Knockout; Phosphorylation; Protein-Serine-Threonine Kinases; Recombinant Proteins; Transcription Factors; Virus Diseases
Immunology and Infectious Disease | Life Sciences | Medicine and Health Sciences
Virus infection, double-stranded RNA, and lipopolysaccharide each induce the expression of genes encoding IFN-alpha and -beta and chemokines, such as RANTES (regulated on activation, normal T cell expressed and secreted) and IP-10 (IFN-gamma inducible protein 10). This induction requires the coordinate activation of several transcription factors, including IFN-regulatory factor 3 (IRF3). The signaling pathways leading to IRF3 activation are triggered by the binding of pathogen-specific products to Toll-like receptors and culminate in the phosphorylation of specific serine residues in the C terminus of IRF3. Recent studies of human cell lines in culture have implicated two noncanonical IkappaB kinase (IKK)-related kinases, IKK-epsilon and Traf family member-associated NF-kappaB activator (TANK)-binding kinase 1 (TBK1), in the phosphorylation of IRF3. Here, we show that purified recombinant IKK-epsilon and TBK1 directly phosphorylate the critical serine residues in IRF3. We have also examined the expression of IRF3-dependent genes in mouse embryonic fibroblasts (MEFs) derived from Tbk1(-/-) mice, and we show that TBK1 is required for the activation and nuclear translocation of IRF3 in these cells. Moreover, Tbk1(-/-) MEFs show marked defects in IFN-alpha and -beta, IP-10, and RANTES gene expression after infection with either Sendai or Newcastle disease viruses or after engagement of the Toll-like receptors 3 and 4 by double-stranded RNA and lipopolysaccharide, respectively. Finally, TRIF (TIR domain-containing adapter-inducing IFN-beta), fails to activate IRF3-dependent genes in Tbk1(-/-) MEFs. We conclude that TBK1 is essential for IRF3-dependent antiviral gene expression.
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Citation: Proc Natl Acad Sci U S A. 2004 Jan 6;101(1):233-8. Epub 2003 Dec 16. Link to article on publisher's site