State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
J Virol. 2018 Nov 27;92(24). doi: 10.1128/JVI.01634-18. Print 2018 Dec 15.
The NS1 protein of influenza A virus is a multifunctional virulence factor that inhibits cellular processes to facilitate viral gene expression. While NS1 is known to interact with RNA and proteins to execute these functions, the cellular RNAs that physically interact with NS1 have not been systematically identified. Here we reveal a NS1 protein-RNA interactome and show that NS1 primarily binds intronic sequences. Among this subset of pre-mRNAs is the RIG-I pre-mRNA, which encodes the main cytoplasmic antiviral sensor of influenza virus infection. This suggested that NS1 interferes with the antiviral response at a posttranscriptional level by virtue of its RNA binding properties. Indeed, we show that NS1 is necessary in the context of viral infection and sufficient upon transfection to decrease the rate of RIG-I intron removal. This NS1 function requires a functional RNA binding domain and is independent of the NS1 interaction with the cleavage and polyadenylation specificity factor CPSF30. NS1 has been previously shown to abrogate RIG-I-mediated antiviral immunity by inhibiting its protein function. Our data further suggest that NS1 also posttranscriptionally alters RIG-I pre-mRNA processing by binding to the RIG-I pre-mRNA. A key virulence factor of influenza A virus is the NS1 protein, which inhibits various cellular processes to facilitate viral gene expression. The NS1 protein is localized in the nucleus and in the cytoplasm during infection. In the nucleus, NS1 has functions related to inhibition of gene expression that involve protein-protein and protein-RNA interactions. While several studies have elucidated the protein interactome of NS1, we still lack a clear and systematic understanding of the NS1-RNA interactome. Here we reveal a nuclear NS1-RNA interactome and show that NS1 primarily binds intronic sequences within a subset of pre-mRNAs, including the RIG-I pre-mRNA that encodes the main cytoplasmic antiviral sensor of influenza virus infection. Our data here further suggest that NS1 is necessary and sufficient to impair intron processing of the RIG-I pre-mRNA. These findings support a posttranscriptional role for NS1 in the inhibition of RIG-I expression.
甲型流感病毒的 NS1 蛋白是一种多功能毒力因子，可抑制细胞过程以促进病毒基因表达。虽然已知 NS1 与 RNA 和蛋白质相互作用以执行这些功能，但尚未系统地鉴定与 NS1 物理相互作用的细胞 RNA。在这里，我们揭示了 NS1 蛋白-RNA 相互作用组，并表明 NS1 主要结合内含子序列。在这组前体 mRNA 中，有一种 RIG-I 前体 mRNA，它编码流感病毒感染的主要细胞质抗病毒传感器。这表明 NS1 通过其 RNA 结合特性在转录后水平干扰抗病毒反应。事实上，我们表明 NS1 在病毒感染的情况下是必需的，并且在转染时足以降低 RIG-I 内含子去除的速率。这种 NS1 功能需要一个功能性 RNA 结合结构域，并且独立于 NS1 与切割和多聚腺苷酸化特异性因子 CPSF30 的相互作用。先前已经表明 NS1 通过抑制其蛋白功能来消除 RIG-I 介导的抗病毒免疫。我们的数据还进一步表明，NS1 通过与 RIG-I 前体 mRNA 结合，也在后转录水平改变 RIG-I 前体 mRNA 的加工。甲型流感病毒的一个关键毒力因子是 NS1 蛋白，它抑制各种细胞过程以促进病毒基因表达。NS1 蛋白在感染期间定位于细胞核和细胞质中。在细胞核中，NS1 具有与基因表达抑制相关的功能，涉及蛋白-蛋白和蛋白-RNA 相互作用。虽然已经有几项研究阐明了 NS1 的蛋白质相互作用组，但我们仍然缺乏对 NS1-RNA 相互作用组的清晰和系统的理解。在这里，我们揭示了一个核 NS1-RNA 相互作用组，并表明 NS1 主要结合一组前体 mRNA 中的内含子序列，包括编码流感病毒感染的主要细胞质抗病毒传感器的 RIG-I 前体 mRNA。我们的数据进一步表明，NS1 是必需的和充分的，以损害 RIG-I 前体 mRNA 的内含子加工。这些发现支持 NS1 在 RIG-I 表达抑制中的转录后作用。
