Understanding the antiviral roles of acellular RNA quality control pathway

摘要 真核细胞使用多层策略来确保基因表达的保真度。研究最深入的学者之一 RNA质量控制途径是一种核糖体相关监测的无义介导的mRNA衰变(NMD) 识别和降解带有提前终止密码子(PTC)的细胞转录的机制。最初 NMD被认为是一种去除细胞中有缺陷的mRNAs的机制，现在已经知道，NMD也调节着表达 5%-10%的细胞转录本在细胞分化、动态平衡、细胞应激等方面具有重要功能 回应，以及更多。此外，最近的研究表明，许多NMD途径的蛋白质具有功能 在对RNA病毒的细胞自主防御中，包括人类致病性甲型病毒、冠状病毒 和黄病毒。作为专性的细胞内寄生虫，这些病毒与细胞内的mrna处理密切相关。 途径，我们可以通过了解NMD的机制是如何改变用途来获得对NMD功能的新见解 对抗病毒感染。我们目前对NMD在病毒感染过程中的功能有一个非常不完整的了解。许多 病毒缺乏PTCs或其他NMD诱导功能，目前尚不清楚NMD蛋白是否识别病毒 RNA以类似于典型的NMD的方式，或通过新的和不寻常的相互作用或机制。此外， 在病毒感染期间，NMD经常在全球范围内下调，这表明病毒有重新连接的机制 抗病毒NMD网络。使用黄病毒寨卡病毒(ZIKV)作为模型RNA病毒，我们的目标是了解 NMD机制与病毒感染之间的分子相互作用。我们将剖析NMD-ZIKV 结合病毒学的多学科方法的蛋白质-蛋白质和蛋白质-RNA相互作用网络 用RNA生物化学和高通量分析将分子相互作用与细胞表型联系起来。特定的 这项研究涉及的问题是：1)NMD蛋白如何相互作用来对抗病毒感染？2)有没有 病毒核糖核酸中触发NMD的特定特征，如果是，NMD机制如何识别它们？ 3)病毒蛋白如何抑制NMD？4)抗病毒NMD功能在重要的蚊子中是否保守 黄病毒的宿主？总而言之，我们的研究将为一种重要的细胞自主抗病毒提供新的见解 防御网。此外，通过研究NMD在病毒感染期间被调控的不寻常方式，我们 希望发现NMD机制本身的新细胞功能。

Abstract Eukaryotic cells use multi-layered strategies to ensure the fidelity of gene expression. One of the best-studied RNA quality control pathways is Nonsense-mediated mRNA decay (NMD), a ribosome-associated surveillance machinery that recognizes and degrades cellular transcripts with premature termination codons (PTC). Initially identified as a mechanism to rid the cell of faulty mRNAs, it is now known that NMD also regulates the expression of 5-10% of cellular transcripts with important functions in cell differentiation, homeostasis, cellular stress responses, and more. In addition, recent studies have shown that many proteins of the NMD pathway function in the cell-autonomous defense against RNA viruses, including human-pathogenic alphaviruses, coronaviruses and flaviviruses. As obligate intracellular parasites, these viruses interface closely with cellular mRNA processing pathways, and we can gain new insight to NMD functions by understanding how the machinery is repurposed to fight viral infection. We currently have a very incomplete picture of NMD functions during viral infection. Many viruses lack PTCs or other NMD-inducing features, and it is not known whether NMD proteins recognize viral RNA in manners similar to canonical NMD, or through new and unusual interactions or mechanisms. Moreover, NMD is often globally downregulated during virus infection, suggesting that viruses have mechanisms to rewire the antiviral NMD network. Using the flavivirus Zika virus (ZIKV) as a model RNA virus, we aim to understand the molecular interactions between the NMD machinery and viral infection. We will dissect the NMD-ZIKV protein-protein and protein-RNA interaction network with a multi-disciplinary approach that combines virology with RNA biochemistry and high-throughput assays to link molecular interactions to cellular phenotypes. Specific questions addressed within this study are: 1) How do NMD proteins interact to fight viral infection? 2) Are there specific features in the viral RNA that trigger NMD, and if so, how are they recognized by the NMD machinery? 3) How do viral proteins inhibit NMD? And 4) Are antiviral NMD functions conserved in the important mosquito host of flaviviruses? Collectively, our study will provide new insight into an important cell-autonomous antiviral defense network. In addition, by studying the unusual ways in which NMD is regulated during virus infection, we hope to discover new cellular functions of the NMD machinery itself.