Translation Regulation by Enterovirus Proteinase

描述(申请人提供)：这项研究的长期目标是了解脊髓灰质炎病毒(PV)和柯萨奇病毒(CVB3)等肠道病毒在刺激受感染细胞中病毒mRNA高效翻译的同时，抑制几乎所有细胞mRNA翻译的机制。我们已经证明，翻译起始因子eIF4G的切割将阻止新的封顶mRNA在核糖体上的组装，而PABP的切割需要与eIF4G协同才能完全阻止翻译。PABP的切割影响翻译的后期步骤，这些步骤目前还不确定，但可能通过mRNA上的5‘-3’相互作用中断核糖体的循环。核糖体循环的机制及其生化要求尚不清楚。此外，肠道病毒和可能大多数其他正链RNA病毒在病毒RNA合成开始之前必须突然关闭感染病毒基因组的翻译。我们推测，PABP裂解也是抑制病毒翻译所必需的。涉及PABP的翻译调节机制现在被认为在几个水平上与mRNA衰变机制相互作用。此外，与靶细胞mRNA3‘端非编码区结合的microRNAs也通过未知的机制沉默翻译，这种机制以某种方式导致mRNAs从多聚体转移到称为P小体和应激颗粒的其他细胞室。我们发现，在PV感染的细胞中，形成应激颗粒的关键因子G3BP被3C酶切割。因此，该病毒正在以一个新的水平攻击整个翻译调控机构。本提案的目的将确定PABP裂解在从病毒翻译到RNA复制的转换中的作用，将确定核糖体循环在这一转换中的作用，并将研究G3BP裂解在病毒复制周期和microRNA翻译沉默中的作用。这些结果将为细胞如何在翻译水平调控基因表达提供新的基础信息，以及翻译启动因子与mRNA沉默/衰退途径之间的相互作用，这将有助于研究病毒对基因表达的调控以及肿瘤和细胞凋亡中的应激反应。 这项工作调查了脊髓灰质炎病毒，人类微小核糖核酸病毒的原型，通过应激颗粒和microRNAs干扰宿主翻译和基因表达调节的新方式。这些机制是细胞基因调控的基础，在癌症和许多非病毒性疾病中被破坏。这些实验将使我们更深入地了解一大类人类病原体如何入侵和杀死细胞(细胞病理学)，并可能为疾病预防提供新的途径，我们将了解更多关于人类细胞的基因调控。

DESCRIPTION (provided by applicant): The long term goal of this research is to understand the mechanism by which enteroviruses such as poliovirus (PV) and Coxsackievirus (CVB3) inactivate translation of nearly all cellular mRNA while stimulating efficient translation of viral mRNA in infected cells. We have shown that cleavage of the translation initiation factor eIF4G will block assembly of new capped mRNA on ribosomes, and that cleavage of PABP is required in concert with eIF4G to completely block translation. PABP cleavage affects late steps in translation that are presently undefined, however likely interrupt ribosome recycling via 5'-3' interactions on mRNA. The mechanism of ribosome recycling and its biochemical requirements are unknown. In addition, enteroviruses and probably most other plus strand RNA viruses must abruptly shut down translation of the infecting viral genome before viral RNA synthesis can begin. We hypothesize that PABP cleavage is also required for inhibition of viral translation. Translation regulation mechanisms involving PABP are now thought to interface with mRNA decay mechanisms on several levels. In addition, microRNAs, which bind to 3' UTR of targeted cellular mRNAs, also silence translation by unknown mechanisms that somehow result in transit of mRNAs from polysomes to other cell compartments called P-bodies and stress granules. We have discovered that G3BP, a key factor that nucleates formation of stress granules, is cleaved in PV-infected cells by 3C protease. Thus, the virus is attacking the overall translation regulatory apparatus at a new level. The aims in this proposal will determine the role of PABP cleavage in the switch from viral translation to RNA replication, will determine the role of ribosome recycling in this switch, and will investigate the function of G3BP cleavage on the viral replication cycle and microRNA-translation silencing. These results will provide new fundamental information on how cells regulate gene expression at the translation level, and the interplay between translation initiation factors and mRNA silencing/decay pathways that will be useful in studies of viral regulation of gene expression and cellular stress responses in cancer and apoptosis. This work investigates new ways that poliovirus, the prototype human picornavirus, interferes with host translation and regulation of gene expression by stress granules and microRNAs. These mechanisms are fundamental for cell gene regulation and are disrupted in cancer and numerous non-viral diseases. These experiments will give us more insight how a large class of human pathogens invade and kill cells (cytopathology) and potentially provide new avenues for disease prevention and we will learn more about gene regulation in human cells.