New Paradigm for Host and Viral Gene Regulation by MERS Coronavirus nsp1

 描述（由申请人提供）：中东呼吸综合征冠状病毒（MCoV）于2012年在沙特阿拉伯出现，并已传播到中东、北非和欧洲的其他国家。虽然MERS很可能是一种人畜共患病，但MCoV可以在人与人之间传播。MCoV感染引起发热、咳嗽和肺炎，导致呼吸衰竭，报告的病死率约为50%。关于MCoV的高毒力和致病机制知之甚少。冠状病毒（CoV）携带约30 kb的单链、正义RNA基因组。感染后，病毒基因组的翻译立即产生两个大的多聚蛋白，它们被加工成15或16个成熟的非结构蛋白（nsp 1-nsp 16），其中大部分参与病毒RNA的合成，而一些具有其他生物学功能。不同CoV的Nsp1蛋白抑制宿主基因表达。抑制宿主基因表达的病毒蛋白通常是主要的毒力因子，因此，CoV nsp1蛋白最有可能在CoV发病机制中发挥关键作用。事实上，小鼠肝炎病毒nsp 1是一个主要的毒力因子，SARS-CoV（SCoV）nsp 1抑制感染细胞中I型干扰素和干扰素刺激基因的产生。不同冠状病毒的nsp 1蛋白使用不同的策略来抑制宿主基因表达;通过与40 S核糖体亚基结合，SCoV nsp 1抑制mRNA翻译并诱导核酸内切mRNA切割，而传染性胃肠炎病毒的nsp 1不诱导mRNA切割，但抑制翻译而不与40 S核糖体亚基结合。我们的数据表明，MCoV nsp 1抑制宿主mRNA的翻译，促进mRNA切割，而不结合40 S亚基和其他实验结果使我们假设，MCoV nsp 1通过使用尚未在任何病毒蛋白中描述的机制来抑制宿主基因表达。本申请旨在阐明MCoV nsp1诱导的翻译抑制和mRNA切割的机制。我们还将阐明在nsp1诱导的翻译抑制条件下，允许MCoV感染细胞中稳健的病毒基因表达的策略。该研究为进一步了解MCoV对宿主基因表达的调控奠定了基础，并在分子水平上拓展了我们对病毒致病性的认识。

 DESCRIPTION (provided by applicant): Middle East respiratory syndrome coronavirus (MCoV) emerged in Saudi Arabia in 2012 and has been disseminated into other countries in the Middle East, North Africa and Europe. Although MERS is most probably a zoonosis, MCoV can spread person-to-person. MCoV infection causes fever, cough and pneumonia leading to respiratory failure, and the reported case fatality is ~50%. Little is known about the mechanisms of MCoV's high virulence and pathogenesis. Coronaviruses (CoVs) carry a single-stranded, positive-sense RNA genome of ~30 kb. Immediately after infection, the translation of the viral genome produces two large polyproteins that are processed into 15 or 16 mature nonstructural proteins (nsp1-nsp16), most of which are involved in viral RNA synthesis, while some have other biological functions. Nsp1 protein of various CoVs inhibits host gene expression. Viral proteins that inhibit host gene expression are often major virulence factors, and, hence, CoV nsp1 proteins most probably play a critical role in CoV pathogenesis. Indeed, mouse hepatitis virus nsp1 is a major virulence factor, and SARS-CoV (SCoV) nsp1 inhibits the production of type I interferon and interferon-stimulated genes in infected cells. Nsp1 proteins of different CoVs use divergent strategies to exert host gene expression suppression; by binding to the 40S ribosomal subunit, SCoV nsp1 inhibits mRNA translation and induces endonucleolytic mRNA cleavage, while nsp1 of transmissible gastroenteritis virus does not induce mRNA cleavage, yet suppresses translation without binding to the 40S ribosomal subunits. Our data that MCoV nsp1 inhibited translation of host mRNAs and promoted mRNA cleavage without binding to the 40S subunits and other experimental results led us to hypothesize that MCoV nsp1 suppresses host gene expression by using mechanisms that have not been described in any viral proteins. This application aims to delineate the mechanisms of MCoV nsp1-induced translation inhibition and mRNA cleavage. We will also clarify the strategy that allows robust viral gene expression in MCoV-infected cells under conditions of nsp1- induced translation inhibition. The proposed studies will provide a foundation for understanding the modulation of host gene expression by MCoV and expand our knowledge of viral pathogenicity at the molecular level.