Department of Virology II, National Institute of Infectious Diseases, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan; Department of Virology II, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi-murayama-shi, Tokyo 208-0011, Japan.
Department of Virology II, National Institute of Infectious Diseases, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
Virology. 2019 Mar;529:226-233. doi: 10.1016/j.virol.2019.01.024. Epub 2019 Jan 29.
Hepatitis C virus (HCV) was shown to activate protein kinase R (PKR), which inhibits expression of interferon (IFN) and IFN-stimulated genes by controlling the translation of newly transcribed mRNAs. However, it is unknown exactly how HCV activates PKR. To address the molecular mechanism(s) of PKR activation mediated by HCV infection, we examined the effects of viral proteins on PKR activation. Here, we show that expression of HCV NS5B strongly induced PKR and eIF2α phosphorylation, and attenuated MHC class I expression. In contrast, expression of Japanese encephalitis virus RNA-dependent RNA polymerase did not induce phosphorylation of PKR. Co-immunoprecipitation analyses showed that HCV NS5B interacted with PKR. Furthermore, expression of NS5B with polymerase activity-deficient mutation failed to phosphorylate PKR, suggesting that RNA polymerase activity is required for PKR activation. These results suggest that HCV activates PKR by association with NS5B, resulting in translational suppression of MHC class I to establish chronic infection.
丙型肝炎病毒（HCV）被证明可以激活蛋白激酶 R（PKR），PKR 通过控制新转录的 mRNA 的翻译来抑制干扰素（IFN）和 IFN 刺激基因的表达。然而，HCV 如何激活 PKR 尚不清楚。为了解决 HCV 感染介导的 PKR 激活的分子机制，我们研究了病毒蛋白对 PKR 激活的影响。在这里，我们表明 HCV NS5B 的表达强烈诱导了 PKR 和 eIF2α 的磷酸化，并减弱了 MHC Ⅰ类的表达。相比之下，日本脑炎病毒 RNA 依赖性 RNA 聚合酶的表达并不诱导 PKR 的磷酸化。共免疫沉淀分析表明 HCV NS5B 与 PKR 相互作用。此外，表达具有聚合酶活性缺陷突变的 NS5B 不能磷酸化 PKR，表明 RNA 聚合酶活性是 PKR 激活所必需的。这些结果表明，HCV 通过与 NS5B 结合来激活 PKR，导致 MHC Ⅰ类的翻译抑制，从而建立慢性感染。
