Translation Regulation by Enterovirus Proteinase

描述（由申请人提供）：本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）等肠道病毒控制感染细胞中细胞和病毒翻译的机制，进而了解翻译和基因表达是如何正常调节的。翻译调控机制现在包括翻译沉默（如microRNAs），并扩展到含有翻译沉默mrna的RNA颗粒的动态组装/拆卸，称为应激颗粒（SG）和p体（PB）。这些结构在压力下协助细胞稳态，并作为mRNPs的临时存储/分类位点，在PBs的情况下，是mRNA衰变的位点。我们发现G3BP是胁迫颗粒形成的关键因子，在pv感染的细胞中被病毒3C蛋白酶裂解，导致细胞中SG的丢失。研究人员提出了实验来识别G3BP与mRNP复合物中调控翻译的起始因子的相互作用，以及G3BP的切割如何取消这一功能。实验还将确定柯萨奇病毒阻断SG形成和所需最少病毒蛋白的替代机制。我们还发现，G3BP表达可组装诱导抗病毒状态的SGs，并阻断PV复制。第二个目标是阐明这种有效抗病毒活性的机制，并发现它是否源于病毒所需因子的隔离，还是SG组装本身发出JNK信号或激活先天免疫的其他途径。我们的新证据表明，应激反应与先天免疫反应在几个层面上联系在一起，形成一个综合的应激/先天免疫反应。我们还确定PV在细胞中分散PB，并在此过程中降解/切割mRNA衰变途径的三个关键组分，Xrn1， Dcp1a和Pan3。我们将阐明PB扩散的机制，并确定在感染过程中这些因子的丢失是否能稳定病毒RNA。总的来说，拟议的研究具有重要意义，因为病毒在RNA颗粒的新水平上攻击翻译/mRNP调节装置，RNA颗粒知之甚少，但在维持细胞稳态和应激生存中发挥关键作用。SG和PBs可能会强烈抑制病毒复制，本研究的新见解可能会导致新的抗病毒策略。

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) control cellular and viral translation in infected cells and in turn, discern how translation and gene expression are regulated normally. Translation regulation mechanisms now encompass translation silencing (e.g. microRNAs) and extend to dynamic assembly/disassembly of RNA granules, called stress granules (SG) and P-bodies (PB) that contain translationally-silenced mRNPs. These structures assist cell homeostasis during stress and serve as temporary storage/triage sites for mRNPs, and in the case of PBs, sites for mRNA decay. We have discovered that G3BP, a key factor that nucleates formation of stress granules, is cleaved in PV-infected cells by virus 3C protease, resulting in loss of SG in cells. Experiments are proposed to discern interactions of G3BP with initiation factors in mRNP complexes that regulate translation and how G3BP cleavage abrogates this function. Experiments will also define alternate mechanism(s) employed by Coxsackievirus to block SG formation and the minimal viral proteins required. We have also shown that G3BP expression assembles SGs that induce antiviral states, and block PV replication. The second aim will elucidate the mechanism of this potent antiviral activity and discover if it stems from sequestration of factors required b the virus or if SG assembly itself signals JNK or other pathways that activate innate immunity. Our emerging evidence suggests stress responses are linked to innate immune responses at several levels to form an integrated stress/innate immune response. We have also determined that PV disperses PB in cells and in the process, degrades/cleaves three critical components of the mRNA decay pathway, Xrn1, Dcp1a and Pan3. We will elucidate the mechanism of PB dispersal and determine if loss of these factors during infection stabilizes viral RNA. Overall, proposed studies are significant since the virus is attacking the translation/mRNP regulatory apparatus at a novel level of RNA granules, which are poorly understood but play key roles in maintaining cell homeostasis and stress survival. SG and perhaps PBs can strongly inhibit virus replication and new insights from this study may lead to novel antiviral strategies.