Murine gammaherpesvirus 68 encoding open reading frame 11 targets TANK binding kinase 1 to negatively regulate the host type I interferon response.
Upon viral infection, type I interferons, such as alpha and beta interferon (IFN-α and IFN-β, respectively), are rapidly induced and activate multiple antiviral genes, thereby serving as the first line of host defense. Many DNA and RNA viruses counteract the host interferon system by modulating the production of IFNs. In this study, we report that murine gammaherpesvirus 68 (MHV-68), a double-stranded DNA virus, encodes open reading frame 11 (ORF11), a novel immune modulator, to block IFN-β production. ORF11-deficient recombinant viruses induced more IFN-β production in fibroblast and macrophage cells than the MHV-68 wild type or a marker rescue virus. MHV-68 ORF11 decreased IFN-β promoter activation by various factors, the signaling of which converges on TBK1-IRF3 activation. MHV-68 ORF11 directly interacted with both overexpressed and endogenous TBK1 but not with IRF3. Physical interactions between ORF11 and endogenous TBK1 were further confirmed during virus replication in fibroblasts using a recombinant virus expressing FLAG-ORF11. ORF11 efficiently reduced interaction between TBK1 and IRF3 and subsequently inhibited activation of IRF3, thereby negatively regulating IFN-β production. Our domain-mapping study showed that the central domain of ORF11 was responsible for both TBK1 binding and inhibition of IFN-β induction, while the kinase domain of TBK1 was sufficient for ORF11 binding. Taken together, these results suggest a mechanism underlying inhibition of IFN-β production by a gammaherpesvirus and highlight the importance of TBK1 in DNA virus replication.


OBJECTIVE
Gammaherpesviruses are important human pathogens, as they are associated with various kinds of tumors. Upon virus infection, the type I interferon pathway is activated by a series of signaling molecules and stimulates antiviral gene expression. To subvert such interferon antiviral responses, viruses are equipped with multiple factors that can inhibit its critical steps. In this study, we took an unbiased genomic approach using a mutant library of murine gammaherpesvirus 68 to screen a novel viral immune modulator that negatively regulates the type I interferon pathway and identified ORF11 as a strong candidate. ORF11-deficient virus infection produced more interferon than the wild type in both fibroblasts and macrophages. During virus replication, ORF11 directly bound to TBK1, a key regulatory protein in the interferon pathway, and inhibited TBK1-mediated interferon production. Our results highlight a crucial role of TBK1 in controlling DNA virus infection and a viral strategy to curtail host surveillance.
Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, South Korea University, Seoul, Republic of Korea.
Hye-Ri
HR
Kang
Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, South Korea University, Seoul, Republic of Korea.
Woo-Chang
WC
Cheong
Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, South Korea University, Seoul, Republic of Korea.
Ji-Eun
JE
Park
Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, South Korea University, Seoul, Republic of Korea.
Seungbo
S
Ryu
Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, South Korea University, Seoul, Republic of Korea.
Hye-Jeong
HJ
Cho
Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, South Korea University, Seoul, Republic of Korea Laboratory of Protein Immunology, Biomedical Research Institutes, Seoul National University Hospital, Seoul, Republic of Korea.
Hyunyee
H
Youn
Department of Molecular Cell Biology, School of Medicine, Sungkyunkwan University, Suwon, Gueonggido, Republic of Korea.
Jin-Hyun
JH
Ahn
Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, South Korea University, Seoul, Republic of Korea moonsong@korea.ac.kr.
Moon Jung
MJ
Song
D000818:Animals; D015536:Down-Regulation; D006566:Herpesviridae Infections / Q000201:enzymology / Q000276:immunology* / Q000821:virology; D054884:Host-Pathogen Interactions; D006801:Humans; D016899:Interferon-beta / Q000235:genetics* / Q000276:immunology; D051379:Mice; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D018144:Rhadinovirus / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
D014764:Viral Proteins; D016899:Interferon-beta; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human