title: Distinct activation of murine interferon-alpha promoter region by IRF-1/ISFG-2 and virus infection.
abstract: Virus infection in mouse L929 cells activates expression of interferon-alpha 4 (IFN-alpha 4), but not IFN-alpha 6. The integrity of a symmetrical sequence, GTAAAGAAAGT (alpha F1 site); (-103 to -93), present in the 35 nucleotide (nt) long inducible element (IE) (-109 to -75) of the alpha 4 promoter region is essential for the virus-induced expression. In the present study, we have shown that the interferon regulatory factor 1 (IRF-1) can induce expression of both IFN-alpha 4 and -alpha 6 in a transient expression assay. Virus infection cooperates with IRF-1 and further enhances transcription from the alpha 4 promoter, but inhibits the IRF-1-mediated expression from the alpha 6 promoter. The virus-mediated induction is determined by both IRF-1 and alpha F1 sites, while activation by IRF-1 in a cotransfection assay is not greatly influenced by the alpha F1 sequence. The activation of IFN-alpha gene promoters by IRF-1 was limited to the transient expression assay. The integrated alpha 4 promoter or the endogenous IFN-alpha genes could not be induced by transfection with IRF-1 expressing plasmid and IRF-1 did not up-regulate expression of the endogenous IRF-1 gene. However, expression of IRF-1 alone was sufficient to up-regulate the expression of two IFN stimulated genes, 2',5' oligoadenylate synthetase (OAS) and interferon stimulated (ISG)-15 gene. These results suggest that induction of IFN-alpha gene expression by virus infection requires cooperation between IRF-1 and another factor(s) that binds to the alpha F1 sequence.
authors.affiliation: Oncology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: W C
authors.initials: WC
authors.lastname: Au
authors.forename: N B
authors.initials: NB
authors.lastname: Raj
authors.forename: R
authors.initials: R
authors.lastname: Pine
authors.forename: P M
authors.initials: PM
authors.lastname: Pitha
mesh_terms: D015088:2',5'-Oligoadenylate Synthetase / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression; D015967:Gene Expression Regulation, Viral; D050856:Interferon Regulatory Factor-1; D016898:Interferon-alpha / Q000235:genetics*; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D009521:Newcastle Disease / Q000235:genetics*; D009522:Newcastle disease virus; D010750:Phosphoproteins / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D016898:Interferon-alpha; C494258:Irf1 protein, mouse; D010750:Phosphoproteins; D012333:RNA, Messenger; D014157:Transcription Factors; D015088:2',5'-Oligoadenylate Synthetase