Flavivirus non-coding RNAs and the Host mRNA Decay Machinery

黄病毒科是一个正义RNA病毒家族，包含许多重要人类 病原体。这些核糖核酸病毒引起细胞病理学的许多分子机制 和疾病没有清楚地描述。细胞信使核糖核酸的衰变机制，特别是5‘-3’途径 在外切核酸酶Xrn1的介导下，在调节基因的丰度和质量方面起着重要作用 在单元格中的表达式。对黄病毒-宿主相互作用的研究不足，但仍然非常重要， 包括病毒RNA如何被细胞mRNA降解机制保护，以及什么是 病毒RNA稳定策略对调节细胞mRNA稳定性的意义。我们有 最近观察到，黄病毒通过使用独特的 病毒RNA的结构化区域。有趣的是，负责这种Xrn1的是5‘UTRIRES区域 抑制丙型肝炎病毒和牛病毒性腹泻病毒。这些观察结果是 这一提议旨在深入了解Xrn1抑制和转录因子的分子机制 被黄病毒RNA扰乱的调控。在目标1中，我们将确定顺序/结构要求 IRES介导的Xrn1抑制，并确定这是否是其他病毒IRES的共同属性 元素。目标2的目标是在机制水平上理解为什么黄病毒对Xrn1的抑制 RNA导致整个5‘-3’信使核糖核酸衰变途径的明显关闭--不仅仅是核外溶解 消化步骤。揭示5‘-3’RNA衰变中衰变因子的相互作用和反馈规律 途径将提供新的见解，以了解细胞如何正常调节这一衰退途径，并将其整合到 基因表达的整个过程。在第三个目标中，我们将扩大我们对Xrn1失速和 调查这是否是细胞用来重塑细胞转录本的方法。在最终目标中，我们将 从细胞和病毒的角度描述Xrn1抑制的关键生物学方面。一个 这一部分的重点将放在黄病毒对细胞mRNA稳定性的失调上，这会导致 细胞基因表达的戏剧性变化可能在丙型肝炎病毒介导的肿瘤发生中发挥重要作用。

The Flaviviridae are a family of positive-sense RNA viruses that contain numerous important human pathogens. Many of the molecular mechanisms that underlie how these RNA viruses cause cytopathology and disease are not clearly described. The cellular mRNA decay machinery, in particularly the 5'-3' pathway mediated by the exoribonuclease Xrn1, plays a major role in regulating the abundance and quality of gene expression in the cell. Understudied, but nevertheless very important aspects of flavivirus-host interactions, include how viral RNAs are protected from degradation by the cellular mRNA decay machinery and what are the implications of the viral RNA stabilization strategies on the regulation of cellular mRNA stability. We have recently observed that flaviviruses repress the activity of Xrn1 through trapping the enzyme using unique structured regions of the viral RNA. Interestingly, it is the 5' UTR IRES region that is responsible for this Xrn1 repression in Hepatitis C virus and Bovine Viral Diarrhea virus. These observations serve as the foundation for this proposal to gain in-depth mechanistic insights into molecular mechanisms of Xrn1 repression and regulation that are disrupted by flavivirus RNAs. In Aim 1, we will identify the sequence/structural requirements of IRES-mediated Xrn1 repression and determine whether this is a common property of other viral IRES elements. The goal of Aim 2 is understand at a mechanistic level why the repression of Xrn1 by flavivirus RNAs results in the apparent shut down of the entire 5'-3' mRNA decay pathway – not just the exonucleolytic digestion step. Uncovering the interplay and feedback regulation of the decay factors in the 5'-3' RNA decay pathway will provide novel insights into how the cell normally regulates this decay pathway and integrate it into the overall process of gene expression. In the third aim we will expand our studies on Xrn1 stalling and investigate whether it is an approach used by the cell to remodel cellular transcripts. In the final Aim, we will characterize key biological aspects of Xrn1 repression from the perspective of both the cell and the virus. A key focus of this part will be on the dysregulation of cellular mRNA stability by flaviviruses that results in dramatic changes in cellular gene expression that could play a significant role in HCV-mediated oncogenesis.