NMD靶向降解CMV基因组RNA3的分子机理及其生物学意义

无义介导的RNA降解（NMD）作为真核细胞中mRNA的质量监控系统，是一种保守的抗病毒防御机制。至今，NMD与RNA病毒的互作研究局限于单分体RNA病毒。鉴于翻译策略的不同，多分体和单分体RNA病毒与NMD的互作关系必然存在差异性。本项目以重要病原黄瓜花叶病毒（CMV）作为研究对象，探究三分体RNA病毒与NMD的互作。前期研究发现：作为移动蛋白（MP）翻译模板的CMV RNA3是NMD的作用靶标。以此作为出发点，界定NMD激活的RNA3特定序列、测定其RNA结构及其与NMD核心组分UPF1的互作，阐明NMD靶向降解 RNA3的作用机理；进而测定病毒蛋白组分对NMD靶向降解RNA3的抑制，分析MP反式过表达、NMD途径的抑制或增强对病毒复制和移动的影响，阐明CMV与NMD的互作关系及其生物学意义。本项目有望揭示三分体RNA病毒CMV克服NMD作用的新策略，为开发抗病毒的新方法提供理论依据。

Nonsense-mediated decay (NMD) that functions as an mRNA quality control in eukaryotic cells is a conserved antiviral defense mechanism. Research on the interaction of NMD with RNA viruses is limited to monopartite RNA viruses so far. Due to the difference in translation strategy, interaction with NMD would be distinct between multi-partite and monopartite RNA viruses. Using the important pathogen cucumber mosaic virus (CMV) as the research objective, this project aims to explore the interaction of tripartite RNA viruses with the NMD pathway. Our preliminary data indicate that viral genome RNA3 as the mRNA for expression of movement protein (MP) is targeted for degradation by NMD. Following this finding, we will investigate the underlying basis of NMD-mediated RNA3 degradation by delimiting the specific RNA3 sequence triggering NMD, determining its RNA structure and interaction with the core component UPF1 (up-frameshift 1) in the NMD pathway. Subsequently, CMV-NMD interaction and its biological relevance will be determined by testing the inhibitory effect of viral proteins on NMD-mediated RNA3 degradation, and analyzing the impact of MP overexpression in trans, inhibition or enhancement of the NMD pathway on viral replication and intercellular movement. Our project would dissect a novel strategy by which tripartite RNA virus CMV overcomes NMD and provide theoretical basis for development of novel antiviral methodology.