Department of Molecular Virology, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
J Virol. 2013 Jan;87(1):489-502. doi: 10.1128/JVI.02186-12. Epub 2012 Oct 24.
Stress granules (SGs) are cytoplasmic foci composed of stalled translation preinitiation complexes induced by environmental stress stimuli, including viral infection. Since viral propagation completely depends on the host translational machinery, many viruses have evolved to circumvent the induction of SGs or co-opt SG components. In this study, we found that expression of Japanese encephalitis virus (JEV) core protein inhibits SG formation. Caprin-1 was identified as a binding partner of the core protein by an affinity capture mass spectrometry analysis. Alanine scanning mutagenesis revealed that Lys(97) and Arg(98) in the α-helix of the JEV core protein play a crucial role in the interaction with Caprin-1. In cells infected with a mutant JEV in which Lys(97) and Arg(98) were replaced with alanines in the core protein, the inhibition of SG formation was abrogated, and viral propagation was impaired. Furthermore, the mutant JEV exhibited attenuated virulence in mice. These results suggest that the JEV core protein circumvents translational shutoff by inhibiting SG formation through an interaction with Caprin-1 and facilitates viral propagation in vitro and in vivo.
应激颗粒（SGs）是由环境应激刺激诱导的停滞的翻译起始复合物组成的细胞质焦点，包括病毒感染。由于病毒的增殖完全依赖于宿主的翻译机制，许多病毒已经进化到可以规避 SG 的诱导或利用 SG 成分。在这项研究中，我们发现日本脑炎病毒（JEV）核心蛋白的表达抑制了 SG 的形成。通过亲和捕获质谱分析鉴定出 Caprin-1 是核心蛋白的结合伴侣。丙氨酸扫描突变显示，JEV 核心蛋白α螺旋中的 Lys（97）和 Arg（98）在与 Caprin-1 的相互作用中起着关键作用。在感染了突变的 JEV 的细胞中，核心蛋白中的 Lys（97）和 Arg（98）被替换为丙氨酸，SG 的形成被抑制，病毒的增殖受到损害。此外，突变的 JEV 在小鼠中表现出减毒。这些结果表明，JEV 核心蛋白通过与 Caprin-1 的相互作用抑制 SG 的形成，从而规避翻译关闭，并促进体外和体内的病毒增殖。
