Interplay between coronaviruses and nonsense-mediated mRNA decay pathway

冠状病毒（CoV）携带大的、单链、正义RNA基因组，其引起多种冠状病毒感染。 人类和家畜的疾病。人CoV（HCoV）通常感染呼吸道， 引起一系列症状，从轻微的感冒到更严重的呼吸道疾病， 如严重急性呼吸综合征（SARS）和中东呼吸综合征（MERS），由两个 高致病性HCoV、SARS-CoV和MERS-CoV。SARS冠状病毒在2002年引起了世界范围的流行， 2003年，导致超过8，000例病例，死亡率约为10%，而MERS-CoV出现在2004年， 沙特阿拉伯，并已传播到中东，北非，欧洲， 和东亚HCoV是对公共卫生的主要威胁，并有可能引起严重的疾病。 负面经济影响。目前，没有针对HCoV的批准的疫苗和治疗剂。 开发针对CoV的有效控制措施需要全面了解病毒 基因表达策略和宿主-CoV相互作用。大量的研究集中在调查CoV 生物学，并大大有助于我们了解冠状病毒复制机制，包括 病毒RNA元件的结构-功能分析以及涉及病毒的病毒蛋白质， 复制和组装。然而，我们对转录后调控的认识仍然存在空白 病毒基因表达，因为只有有限数量的研究已经解决了冠状病毒研究的这一领域。 特别是，很少有人知道的顺式作用的病毒RNA元件和反式作用的主机和病毒的因素 其调节CoV mRNA转录稳定性。病毒学中一个新兴的研究领域是了解 病毒和宿主mRNA监视途径之间的相互作用，防止病毒的生成/积累。 不需要的基因产物我们已经证明，CoV mRNAs是无义介导的 mRNA衰变（NMD）途径，宿主mRNA监视途径之一，病毒N蛋白保护 来自NMD的CoV mRNA。我们的数据表明N-介导的NMD抑制对于有效的病毒感染的重要性。 复制的本申请将通过测试NMD途径和CoV之间的相互作用来研究NMD途径和CoV之间的相互作用。 以下假设：UPF 1，NMD的主要协调者，结合CoV mRNA的3' UTR， 特定的基序，经历磷酸化，并招募SMG 6，一种核酸内切酶，导致核酸内切酶解， RNA切割; N结合NMD靶标的3'UTR并阻止NMD因子接近这些靶点。 靶向和/或N与NMD因子相互作用并将其从NMD途径隔离;和CoV 对NMD易感性增加的突变体不能像亲本病毒那样有效地复制。的 从这些研究中获得的数据将提供对CoV mRNAs和N-介导的NMD的机制见解。 NMD途径抑制，并将揭示通过以下途径减弱CoV的新策略的可行性： 增加对NMD途径的敏感性。

Coronaviruses (CoVs), which carry a large, single-stranded, positive-sense RNA genome, cause a variety of diseases in humans and domestic animals. Human CoVs (HCoVs) usually infect the respiratory tract and cause a range of symptoms varying from mild, such as the common cold, to more serious respiratory illnesses like severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), caused by two highly pathogenic HCoVs, SARS-CoV and MERS-CoV. SARS-CoV caused a worldwide epidemic in 2002- 2003, resulting in more than 8,000 cases with an approximate mortality of 10%, while MERS-CoV emerged in Saudi Arabia in 2012 and has been disseminated into other countries in the Middle East, North Africa, Europe, and East Asia. HCoVs represent a major threat to public health and have the potential to cause a significant negative economic impact. Currently, there are no approved vaccines and therapeutic agents against HCoVs. The development of effective control measures against CoVs requires a comprehensive understanding of viral gene expression strategies and host-CoV interactions. A plethora of studies have focused on investigating CoV biology and have significantly contributed to our understanding of CoV replication mechanisms, including the structure-function analyses of viral RNA elements as well as the viral proteins that are involved in viral replication and assembly. However, there are still gaps in our knowledge of the post-transcriptional regulation of viral gene expression, as only a limited number of studies have addressed this area of CoV research. Particularly, very little is known about the cis-acting viral RNA elements and trans-acting host and viral factors that regulate CoV mRNA transcript stability. One newly emerging research area in virology is understanding interactions between viruses and host mRNA surveillance pathways that prevent generation/accumulation of unwanted gene products. We have demonstrated that CoV mRNAs are the targets of the nonsense-mediated mRNA decay (NMD) pathway, one of the host mRNA surveillance pathways, and that viral N protein protects CoV mRNAs from NMD. Our data suggest the importance of N-mediated NMD suppression for efficient virus replication. The present application will study the interplay between the NMD pathway and CoVs by testing the following hypotheses: UPF1, the principal orchestrator of NMD, binds to the 3’ UTR of CoV mRNAs having specific motifs, undergoes phosphorylation, and recruits SMG6, an endonuclease, leading to endonucleolytic RNA cleavage; N binds to the 3’ UTRs of NMD targets and prevents an NMD factor(s) from accessing these targets and/or N interacts with an NMD factor(s) and sequesters it away from the NMD pathway; and CoV mutants having an increased susceptibility to NMD, cannot replicate as efficiently as the parental viruses. The data obtained from these studies will provide mechanistic insights into NMD of CoV mRNAs and N-mediated NMD pathway suppression, and will reveal the feasibility of novel strategies for attenuating CoVs through increased susceptibility to the NMD pathway.