부산대학교 도서관

We previously identified a subset of interferon-stimulated genes (ISGs) upregulated by West Nile virus (WNV) infection in wild-type mouse embryo fibroblasts (MEFs) after viral proteins had inhibited type I interferon (IFN)-mediated JAK-STAT signaling and also in WNV-infected RIG-I-/-, MDA5-/-, STAT1-/-, STAT2-/-, IFNAR-/-, IRF3-/-, IRF7-/-, and IRF3/7-/- MEFs. In this study, ISG upregulation by WNV infection in IFNAR-/- MEFs was confirmed by transcriptome sequencing (RNA-seq). ISG upregulation by WNV infection was inhibited in RIG-I/MDA5-/- MEFs. ISGs were upregulated in IRF1-/- and IRF5-/- MEFs but only minimally upregulated in IRF3/5/7-/- MEFs, suggesting redundant IRF involvement. We previously showed that a single proximal interferon-stimulated response element (ISRE) in the Oas1a and Oas1b promoters bound the ISGF3 complex after type I IFN treatment. In this study, we used wild-type and mutant promoter luciferase reporter constructs to identify critical regions in the Oas1b and Ifit1 promoters for gene activation in infected IFNAR-/- MEFs. Two ISREs were required in both promoters. Mutation of these ISREs in an Ifit1 promoter DNA probe reduced in vitro complex formation with infected nuclear extracts. An NF-k B inhibitor decreased Ifit1 promoter activity in cells and in vitro complex formation. IRF3 and p50 promoter binding was detected by chromatin immunoprecipitation (ChIP) for upregulated ISGs with two proximal ISREs. The data indicate that ISREs function cooperatively to upregulate the expression of some ISGs when type I IFN signaling is absent, with the binding complex consisting of IRF3, IRF5, and/or IRF7 and an NFkB component(s) as well as other, as-yet-unknown factors. [ABSTRACT FROM AUTHOR]