title: Glycogen synthase kinase 3 negatively regulates IFN regulatory factor 3 transactivation through phosphorylation at its linker region.
abstract: Upon virus infection, the host innate immune response is initiated through the activation of IFN regulatory factor 3 (IRF3) and NF-κB signaling pathways to induce IFN production. Previously, we demonstrated EBV BGLF4 kinase suppresses IRF3 function in a kinase activity-dependent manner. The replacement of Ser123, Ser173 and Thr180 into alanines at the proline-rich linker region of IRF3 abolishes BGLF4-mediated suppression. In this study, we show that BGLF4 phosphorylates glutathione-S-transferase (GST)-IRF3(110-202), but not GST-IRF3(110-202)3A mutant (S123/S173/T180A) in vitro. Compared with activation mimicking mutant IRF3(5D), the phosphorylation-defective IRF3(5D)3A shows a higher transactivation activity in reporter assays, whereas the phosphorylation-mimicking IRF3(5D)2D1E, with Ser123 and Ser173 mutated to aspartate and Thr180 to glutamate, has a much lower activity. To explore whether similar cellular regulation also exists in the absence of virus infection, candidate cellular kinases were predicted and the transactivation activity of IRF3 was examined with various kinase inhibitors. Glycogen synthase kinase 3 (GSK3) inhibitor LiCl specifically enhanced both IRF3(5D) and wild type IRF3 activity, even without stimulation. Expression of constitutive active GSK3β(S9A) represses LiCl-mediated enhancement of IRF3 transactivation activity. In vitro, both GSK3α and GSK3β phosphorylate IRF3 at the linker region. Collectively, data here suggest GSK3 phosphorylates IRF3 linker region in a way similar to viral kinase BGLF4.
authors.affiliation: 1Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Jiin-Tarng
authors.initials: JT
authors.lastname: Wang
authors.forename: Ling-Shih
authors.initials: LS
authors.lastname: Chang
authors.forename: Chun-Jen
authors.initials: CJ
authors.lastname: Chen
authors.forename: Shin-Lian
authors.initials: SL
authors.lastname: Doong
authors.forename: Chou-Wei
authors.initials: CW
authors.lastname: Chang
authors.forename: Mei-Ru
authors.initials: MR
authors.lastname: Chen
mesh_terms: D005982:Glutathione Transferase / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D004854:Herpesvirus 4, Human / Q000378:metabolism*; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000235:genetics / Q000378:metabolism*; D007371:Interferon-gamma / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D015533:Transcriptional Activation / Q000187:drug effects; D014760:Viral Fusion Proteins / Q000378:metabolism; D014777:Virus Diseases / Q000276:immunology*
chemical_list: C072324:BGLF2 protein, Epstein-barr virus; C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D014760:Viral Fusion Proteins; D007371:Interferon-gamma; D005982:Glutathione Transferase; D038362:Glycogen Synthase Kinase 3
keywords: EBV BGLF4 kinase; GSK3; IRF3; proline-rich linker region