Schröder Martina, Baran Marcin, Bowie Andrew G
Viral Immune Evasion Group, School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland.
EMBO J. 2008 Aug 6;27(15):2147-57. doi: 10.1038/emboj.2008.143. Epub 2008 Jul 17.
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.
病毒可被不同类别的模式识别受体（PRR）检测到，如Toll样受体和RIG样解旋酶。PRR的激活会通过IKKε和TBK1导致干扰素（IFN）调节因子3（IRF3）和IRF7的激活，进而诱导IFN-β的产生。痘苗病毒（VACV）编码的蛋白质可操纵宿主信号传导，有时通过靶向未鉴定的蛋白质来实现。在此，我们描述了一种新型的VACV蛋白K7，它可通过阻止TBK1/IKKε介导的IRF激活来抑制PRR诱导的IFN-β产生。我们确定DEAD盒蛋白3（DDX3）是K7的宿主靶点。DDX3的表达增强了TBK1/IKKε对Ifnb启动子的诱导作用，而敲低DDX3则抑制了这种作用以及病毒或双链RNA诱导的IRF3激活。此外，显性负性DDX3抑制了病毒、双链RNA和胞质DNA刺激的Ccl5启动子诱导，这也是TBK1/IKKε依赖性的。K7的结合和对Ifnb诱导的增强都定位于DDX3的N端。此外，病毒感染诱导了DDX3与IKKε之间的关联。因此，本研究首次表明DEAD盒解旋酶参与了TBK1/IKKε介导的IRF激活和Ifnb启动子诱导。
