title: Viral targeting of DEAD box protein 3 reveals its role in TBK1/IKKepsilon-mediated IRF activation.
abstract: Viruses are detected by different classes of pattern recognition receptors (PRRs), such as Toll-like receptors and RIG-like helicases. Engagement of PRRs leads to activation of interferon (IFN)-regulatory factor 3 (IRF3) and IRF7 through IKKepsilon and TBK1 and consequently IFN-beta induction. Vaccinia virus (VACV) encodes proteins that manipulate host signalling, sometimes by targeting uncharacterised proteins. Here, we describe a novel VACV protein, K7, which can inhibit PRR-induced IFN-beta induction by preventing TBK1/IKKepsilon-mediated IRF activation. We identified DEAD box protein 3 (DDX3) as a host target of K7. Expression of DDX3 enhanced Ifnb promoter induction by TBK1/IKKepsilon, whereas knockdown of DDX3 inhibited this, and virus- or dsRNA-induced IRF3 activation. Further, dominant-negative DDX3 inhibited virus-, dsRNA- and cytosolic DNA-stimulated Ccl5 promoter induction, which is also TBK1/IKKepsilon dependent. Both K7 binding and enhancement of Ifnb induction mapped to the N-terminus of DDX3. Furthermore, virus infection induced an association between DDX3 and IKKepsilon. Therefore, this study shows for the first time the involvement of a DEAD box helicase in TBK1/IKKepsilon-mediated IRF activation and Ifnb promoter induction.
authors.affiliation: Viral Immune Evasion Group, School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Martina
authors.initials: M
authors.lastname: Schröder
authors.forename: Marcin
authors.initials: M
authors.lastname: Baran
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Bowie
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D018946:Chemokine CCL5 / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism*; D050839:Interferon Regulatory Factor-7 / Q000378:metabolism; D016899:Interferon-beta / Q000096:biosynthesis; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051192:Receptors, Pattern Recognition / Q000378:metabolism; D014616:Vaccinia virus / Q000378:metabolism; D014764:Viral Proteins / Q000502:physiology*
chemical_list: D018946:Chemokine CCL5; C494232:IRF3 protein, human; C494234:IRF7 protein, human; D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; D051192:Receptors, Pattern Recognition; D014764:Viral Proteins; D016899:Interferon-beta; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; D051550:I-kappa B Kinase; C119332:DDX3X protein, human; D053487:DEAD-box RNA Helicases