Flavivirus non-coding RNAs and the Host mRNA Decay Machinery

黄病毒科（Flaviviridae）是一个正义RNA病毒家族，其包含许多重要的人类基因组。 病原体这些RNA病毒引起细胞病理学的许多分子机制 疾病没有明确描述。细胞mRNA衰变机制，特别是5 '-3'途径 由核糖核酸外切酶Xrn 1介导，在调节基因的丰度和质量方面起着重要作用 细胞中的表达。黄病毒与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衰变机制保护而不被降解， 病毒RNA稳定化策略对细胞mRNA稳定性调节的影响。我们有 最近观察到，黄病毒通过使用独特的捕获酶来抑制Xrn 1的活性， 病毒RNA的结构化区域。有趣的是，正是5' UTR IRES区域负责这个Xrn 1 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Xrn 1抑制的分子机制， 调节被黄病毒RNA破坏。在目标1中，我们将确定序列/结构要求 IRES介导的Xrn 1抑制，并确定这是否是其他病毒IRES的共同特性 元素目的2的目标是在机制水平上理解为什么黄病毒抑制Xrn 1 RNA导致整个5 '-3' mRNA衰变途径的明显关闭-而不仅仅是核酸外切酶， 消化步骤。揭示5 '-3' RNA衰变中衰变因子的相互作用和反馈调节 这将为细胞如何正常调节这种衰变途径并将其整合到细胞中提供新的见解。 基因表达的整个过程。在第三个目标中，我们将扩展我们对Xrn 1失速的研究， 研究它是否是细胞用来重塑细胞转录本的一种方法。在最后的目标中，我们将 从细胞和病毒的角度描述Xrn 1抑制的关键生物学方面。一 本部分的重点是黄病毒引起的细胞mRNA稳定性失调， 细胞基因表达的显著变化可能在HCV介导的肿瘤发生中起重要作用。

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.