Mibayashi Masaki, Martínez-Sobrido Luis, Loo Yueh-Ming, Cárdenas Washington B, Gale Michael, García-Sastre Adolfo
Department of Microbiology, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, New York, NY 10029, USA.
J Virol. 2007 Jan;81(2):514-24. doi: 10.1128/JVI.01265-06. Epub 2006 Nov 1.
The retinoic acid-inducible gene I product (RIG-I) has been identified as a cellular sensor of RNA virus infection resulting in beta interferon (IFN-beta) induction. However, many viruses are known to encode viral products that inhibit IFN-beta production. In the case of influenza A virus, the viral nonstructural protein 1 (NS1) prevents the induction of the IFN-beta promoter by inhibiting the activation of transcription factors, including IRF-3, involved in IFN-beta transcriptional activation. The inhibitory properties of NS1 appear to be due at least in part to its binding to double-stranded RNA (dsRNA), resulting in the sequestration of this viral mediator of RIG-I activation. However, the precise effects of NS1 on the RIG-I-mediated induction of IFN-beta have not been characterized. We now report that the NS1 of influenza A virus interacts with RIG-I and inhibits the RIG-I-mediated induction of IFN-beta. This inhibition was apparent even when a mutant RIG-I that is constitutively activated (in the absence of dsRNA) was used to trigger IFN-beta production. Coexpression of RIG-I, its downstream signaling partner, IPS-1, and NS1 resulted in increased levels of RIG-I and NS1 within an IPS-1-rich, solubilization-resistant fraction after cell lysis. These results suggest that RIG-I, IPS-1, and NS1 become part of the same complex. Consistent with this idea, NS1 was also found to inhibit IFN-beta promoter activation by IPS-1 overexpression. Our results indicate that, in addition to sequestering dsRNA, the NS1 of influenza A virus binds to RIG-I and inhibits downstream activation of IRF-3, preventing the transcriptional induction of IFN-beta.
维甲酸诱导基因I产物（RIG-I）已被确定为RNA病毒感染的细胞传感器，可导致β干扰素（IFN-β）的诱导。然而，已知许多病毒编码抑制IFN-β产生的病毒产物。就甲型流感病毒而言，病毒非结构蛋白1（NS1）通过抑制参与IFN-β转录激活的转录因子（包括IRF-3）的激活来阻止IFN-β启动子的诱导。NS1的抑制特性似乎至少部分归因于其与双链RNA（dsRNA）的结合，导致这种RIG-I激活的病毒介质被隔离。然而，NS1对RIG-I介导的IFN-β诱导的确切影响尚未得到表征。我们现在报告，甲型流感病毒的NS1与RIG-I相互作用并抑制RIG-I介导的IFN-β诱导。即使使用组成性激活的突变RIG-I（在没有dsRNA的情况下）来触发IFN-β产生，这种抑制作用也很明显。RIG-I、其下游信号伙伴IPS-1和NS1的共表达导致细胞裂解后富含IPS-1、抗溶解部分内RIG-I和NS1水平升高。这些结果表明，RIG-I、IPS-1和NS1成为同一复合物的一部分。与此观点一致，还发现NS1通过过表达IPS-1抑制IFN-β启动子激活。我们的结果表明，除了隔离dsRNA外，甲型流感病毒的NS1还与RIG-I结合并抑制IRF-3的下游激活，从而阻止IFN-β的转录诱导。
