title: Zebrafish IRF1 regulates IFN antiviral response through binding to IFNϕ1 and IFNϕ3 promoters downstream of MyD88 signaling.
abstract: In mammals, type I IFNs (mainly IFN-α/β) are primarily regulated by transcription factors of the IFN regulatory factor (IRF) family. Fish IFNs do not show a one-to-one orthologous relationship with mammalian type I IFN homologues. Using a bacterial one-hybrid reporter screening system and an overexpression approach to explore the molecular mechanism underlying fish IFN induction, we identified zebrafish Danio rerio IRF (DrIRF)1 as a positive regulator of the fish IFN antiviral response. Among 12 zebrafish IRF family genes, DrIRF1 is most abundant in zebrafish immune tissues, including head kidney and spleen; upon virus infection, it is one of most significantly induced genes. Overexpression of DrIRF1 induces the expression of IFN and IFN-stimulated genes, hence protecting epithelioma papulosum cyprini cells against spring viremia of carp virus infection. As a transcription factor with constitutively nuclear retention, DrIRF1 directly binds to the IFN-stimulated regulatory element/IRF-binding element sites of zebrafish IFN promoters, which are dependent on four conserved amino acids of the N-terminal DNA-binding domain helix α3 motif. Mutation of either residue reveals a differential requirement for DrIRF1-mediated activation of zebrafish IFNϕ1 and IFNϕ3 promoters. Notably, C-terminal phosphorylation of DrIRF1 is observed and is not required for in vitro binding of DrIRF1 to fish IFN promoters. Unlike DrIRF3 and DrIRF7, which are responsible for differential expression of zebrafish IFNϕ1 and IFNϕ3 through the retinoic acid-inducible gene I-like receptor pathway, DrIRF1 works in concert with MyD88 to activate zebrafish IFNϕ3 but not IFNϕ1. These results provide insights into the evolving function of IRF1 as a positive IFN regulator.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China ybzhang@ihb.ac.cn jfgui@ihb.ac.cn.
authors.forename: Yi-Bing
authors.initials: YB
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Qi-Min
authors.initials: QM
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Qi-Ya
authors.initials: QY
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China ybzhang@ihb.ac.cn jfgui@ihb.ac.cn.
authors.forename: Jian-Fang
authors.initials: JF
authors.lastname: Gui
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D023061:Gene Order; D050856:Interferon Regulatory Factor-1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007372:Interferons / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D016415:Sequence Alignment; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D014777:Virus Diseases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015027:Zebrafish
chemical_list: D050856:Interferon Regulatory Factor-1; D053594:Myeloid Differentiation Factor 88; D014157:Transcription Factors; D007372:Interferons