Department of Food Science, National Quemoy University, Kinmen, Taiwan.
Institute of Fisheries Science, College of Life Science, National Taiwan Universitygrid.19188.39, Taipei, Taiwan.
J Virol. 2021 Aug 10;95(17):e0236420. doi: 10.1128/JVI.02364-20.
Nervous necrosis virus (NNV) belongs to the genus of the Nodaviridae family and is the main cause of viral nervous necrosis disease in marine fish larvae and juveniles worldwide. The NNV virion contains two positive-sense, single-stranded RNA genomes, which encode RNA-dependent RNA polymerase, coat protein, and B2 protein. Interestingly, NNV infection can shut off host translation in orange-spotted grouper (Epinephelus coioides) brain cells; however, the detailed mechanisms of this action remain unknown. In this study, we discovered that the host translation factor, polyadenylate binding protein (PABP), is a key target during NNV takeover of host translation machinery. Additionally, ectopic expression of NNV coat protein is sufficient to trigger nuclear translocalization and degradation of PABP, followed by translation shutoff. A direct interaction between NNV coat protein and PABP was demonstrated, and this binding requires the NNV coat protein N-terminal shell domain and PABP proline-rich linker region. Notably, we also showed that degradation of PABP during later stages of infection is mediated by the ubiquitin-proteasome pathway. Thus, our study reveals that the NNV coat protein hijacks host PABP, causing its relocalization to the nucleus and promoting its degradation to stimulate host translation shutoff. Globally, more than 200 species of aquacultured and wild marine fish are susceptible to NNV infection. Devastating outbreaks of this virus have been responsible for massive economic damage in the aquaculture industry, but the molecular mechanisms by which NNV affects its host remain largely unclear. In this study, we show that NNV hijacks translation in host brain cells, with the viral coat protein binding to host PABP to promote its nuclear translocalization and degradation. This previously unknown mechanism of NNV-induced host translation shutoff greatly enhances the understanding of NNV pathogenesis and provides useful insights and novel tools for development of NNV treatments, such as the use of orange-spotted grouper brain cells as an model system.
神经坏死病毒 (NNV) 属于诺达病毒科的正粘病毒属,是世界范围内导致海洋鱼类仔鱼和幼鱼病毒性神经坏死病的主要病原体。NNV 病毒粒子包含两条正链、单链 RNA 基因组,分别编码 RNA 依赖性 RNA 聚合酶、衣壳蛋白和 B2 蛋白。有趣的是,NNV 感染可使橙斑鮨(Epinephelus coioides)脑细胞中的宿主翻译关闭;然而,其作用的详细机制尚不清楚。在本研究中,我们发现宿主翻译因子多聚腺苷酸结合蛋白 (PABP) 是 NNV 接管宿主翻译机制时的关键靶标。此外,NNV 衣壳蛋白的异位表达足以触发 PABP 的核转位和降解,随后导致翻译关闭。证明了 NNV 衣壳蛋白与 PABP 之间存在直接相互作用,这种结合需要 NNV 衣壳蛋白的 N 端壳域和 PABP 的富含脯氨酸的连接区。值得注意的是,我们还表明感染后期 PABP 的降解是由泛素-蛋白酶体途径介导的。因此,我们的研究揭示了 NNV 衣壳蛋白劫持宿主 PABP,导致其重新定位到细胞核并促进其降解,从而刺激宿主翻译关闭。 全球有 200 多种养殖和野生海洋鱼类易感染 NNV。这种病毒的毁灭性爆发已对水产养殖业造成巨大的经济损失,但 NNV 影响宿主的分子机制在很大程度上仍不清楚。在本研究中,我们表明 NNV 劫持宿主脑细胞中的翻译,病毒衣壳蛋白与宿主 PABP 结合,促进其核转位和降解。这种以前未知的 NNV 诱导的宿主翻译关闭机制极大地增强了对 NNV 发病机制的理解,并为 NNV 治疗方法的开发提供了有用的见解和新工具,例如利用橙斑鮨脑细胞作为模型系统。