Promoter organization of the interferon-A genes differentially affects virus-induced expression and responsiveness to TBK1 and IKKepsilon.
Virus-induced expression of interferon (IFN)-A genes is regulated by two members of the IFN regulatory factor (IRF) family, IRF-3 and IRF-7, which are activated by phosphorylation during viral infection by the IKK-related serine/threonine kinases TBK1 and IkappaB kinase epsilon (IKKepsilon). In this study, we demonstrate that three IRF-binding sites located in the virus-responsive element mediate the transcriptional activation of the IFN-A4 promoter by IRF-3. The precise arrangement of these IRF elements is required for synergistic activation of the IFN-A4 promoter following Newcastle disease virus infection or activation by TBK1 or IKKepsilon. The ordered assembly of IRF-3 multimers on the promoter also determines cooperative recruitment of IRF-3 and CREB-binding protein and differential virus-induced expression of IFN-A4 gene promoter compared with IFN-A11. Naturally occurring nucleotide substitutions disrupt two of the IRF elements in the IFN-A11 gene promoter, leading to a dramatic decrease in IRF-3 and CREB-binding protein recruitment and in IRF-3-dependent transcription. Transcription of the IFN-A4 promoter by IRF-7 is mediated by two IRF elements; promoter mutants that carry a reversed IRF element retain the ability to respond to IKKepsilon or TBK1 expression in the presence of IRF-7 but lose the capacity to respond to virus or kinase-induced IRF-3. Interestingly, IKKepsilon or TBK1 stimulates the IRF-7-mediated transcription of IFN-A11, although at a lesser extent compared with IFN-A4. Our data indicate that virus-induced expression of IFN-A genes is dictated by the organization of IRF elements within the IFN-A promoters and that the differential IFN-A gene expression, based on the IRF-3 responsiveness, is partially compensated in the presence of IRF-7 when both factors are activated by IKKepsilon or TBK1.
Civas
Ahmet
A
UPR 2228-CNRS, Laboratoire de Régulation Transcriptionnelle et Maladies Génétiques, UFR Biomédicale des Saints-Pères, Université Paris V, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France. ahmet.civas@univ-paris5.fr
Génin
Pierre
P
Morin
Pierre
P
Lin
Rongtuan
R
Hiscott
John
J
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D015151:Immunoblotting; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D050839:Interferon Regulatory Factor-7 / Q000378:metabolism; D016898:Interferon-alpha / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; D016898:Interferon-alpha; C498588:Tbk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; D051550:I-kappa B Kinase