title: ISG15 enhances the innate antiviral response by inhibition of IRF-3 degradation.
abstract: The transcription factor, interferon regulatory Factor 3 (IRF-3) plays a critical role in the activation of an antiviral innate immune response. However the transcriptional activity of IRF-3 is tightly regulated by a proteosome mediated degradation. We describe here a novel mechanism by which the activity of IRF-3 is stabilized in infected cells. We have shown that both interferon treatment and NDV infection profoundly increase conjugation of interferon induced ubiquitin- like protein ISG15 to cellular proteins. ISGylated IRF-3 could be detected both in interferon treated and virus-infected cells. ISG15, subverts the ubiquitin mediated degradation of IRF-3 in NDV infected 2fTGH cells and enhances the NDV mediated transactivation of interferonbeta promoter and the translocation of activated IRF-3 to the nucleus. The relative levels of IRF-3 were significantly lower in NDV infected ISG15 null MEF, than in wt MEF. While ISG15 null MEF were more permissive to VSV replication their sensitivity to the antiviral effect of interferon was not modulated. These results reveal that virus mediated subversion of the antiviral response by proteolysis of IRF-3 is counteracted by induction of ISG15 expression and that ISGylation provides a feedback mechanism, which enhances the host innate antiviral response via IRF-3 stabilization.
authors.affiliation: The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD 21231, USA.
authors.forename: G
authors.initials: G
authors.lastname: Lu
authors.forename: J T
authors.initials: JT
authors.lastname: Reinert
authors.forename: I
authors.initials: I
authors.lastname: Pitha-Rowe
authors.forename: A
authors.initials: A
authors.lastname: Okumura
authors.forename: M
authors.initials: M
authors.lastname: Kellum
authors.forename: K P
authors.initials: KP
authors.lastname: Knobeloch
authors.forename: B
authors.initials: B
authors.lastname: Hassel
authors.forename: P M
authors.initials: PM
authors.lastname: Pitha
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D045463:Avulavirus Infections / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000172:deficiency / Q000502:physiology*; D010450:Endopeptidases / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism*; D016899:Interferon-beta / Q000235:genetics; D051379:Mice; D009522:Newcastle disease virus / Q000276:immunology; D011401:Promoter Regions, Genetic; D061988:Proteasome Inhibitors; D011485:Protein Binding; D011489:Protein Denaturation; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism; D018353:Rhabdoviridae Infections / Q000276:immunology; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism; D043222:Ubiquitin Thiolesterase; D014452:Ubiquitins / Q000172:deficiency / Q000502:physiology; D014721:Vesicular stomatitis Indiana virus / Q000276:immunology; D014775:Virus Activation; D014779:Virus Replication
chemical_list: D016207:Cytokines; C489550:G1p2 protein, mouse; D050838:Interferon Regulatory Factor-3; D061988:Proteasome Inhibitors; D011506:Proteins; D025801:Ubiquitin; D014452:Ubiquitins; D016899:Interferon-beta; D010450:Endopeptidases; C118306:Usp18 protein, mouse; D043222:Ubiquitin Thiolesterase