Mechanisms of virus-mediated compartmentalization of the host translational machinery

 描述(申请人提供)：作为主要的细胞内病原体，病毒需要宿主的生物合成机制。一个基本的要求是合成新病毒蛋白的宿主翻译机制。病毒选择宿主翻译机制并避开固有宿主防御的机制尚不清楚，天然宿主防御作用可降解病毒mRNA，减少细胞蛋白质合成，以防止或减少病毒蛋白质的合成。这个项目的目标是确定哺乳动物呼肠孤病毒重新编程宿主翻译机制以优先合成病毒蛋白的机制。特别是，该项目将专注于病毒介导的翻译机制的区隔，这是一种新的致病机制，通过它可以在感染诱导的应激期间保持病毒蛋白质的合成。要测试的假设是，呼肠孤病毒通过以下途径促进其病毒α的翻译：(1)在被称为病毒工厂的细胞质中，将翻译因子和核糖体亚基分开；(2)通过隔离Gadd34/蛋白磷酸酶1复合体在病毒工厂内使eIF2mRNA去磷酸化，从而保护病毒mRNA的翻译免受应激诱导的蛋白质合成抑制；以及(3)直接修饰核糖体并改变其功能，以促进非规范病毒mRNAs的翻译。有三个目的被提出：(1)确定在呼肠孤病毒感染细胞中宿主细胞翻译机制在病毒工厂内被区划的机制(S)；(2)确定在呼肠孤病毒工厂内整合的应激反应的激活和细胞Gadd34和蛋白磷酸酶1的区划是否促进呼肠孤病毒mRNAs的翻译；以及(3)确定病毒非结构蛋白σNS在促进感染细胞中呼肠孤病毒mRNAs翻译中的作用。这项工作的预期结果是确定病毒工厂内宿主翻译机制分区所需的病毒因子，了解呼肠孤病毒在面对正在进行的磷酸化eIF2α和激活整合应激反应时复制的机制，以及更好地了解呼肠孤病毒蛋白σNS在选择宿主翻译机制和修改核糖体功能中的作用。我们预计，这项提议的一个重要结果将是关于克服宿主固有防御的病毒策略的新的基本信息。

 DESCRIPTION (provided by applicant): As obligate intracellular pathogens, viruses require the host biosynthetic machinery. A fundamental requirement is the host translational machinery for the synthesis of new viral proteins. The mechanisms by which viruses co-opt the host translational machinery and avoid the innate host defenses that act to degrade viral mRNA and diminish cellular protein synthesis to prevent or lessen the synthesis of viral proteins are not understood. The goal of this project is to define mechanisms by which mammalian reoviruses reprogram the host translational machinery to preferentially synthesize viral proteins. In particular, the project will focus on virus-mediated compartmentalization of the translational machinery, a novel pathogenic mechanism by which viral protein synthesis can be maintained during infection-induced stress. The hypotheses to be tested are that reovirus promotes the translation of its viral mRNAs by: (1) compartmentalizing translation factors and ribosomal subunits within defined sites of viral replication in the cytosol called viral factories; (2) by sequestering the GADD34/protein phosphatase 1 complex that dephosphorylates eIF2α within viral factories, thus, protecting translation of viral mRNAs from stress-induced inhibition of protein synthesis; and (3) by directly modifying the ribosome and altering its function to promote translation of non-canonical viral mRNA. Three Aims are proposed: (1) To identify mechanism(s) by which the host cell translational machinery is compartmentalized within viral factories in reovirus-infected cells; (2) To determine whether activation of the integrated stress response and compartmentalization of cellular GADD34 and protein phosphatase 1 within reovirus factories promotes translation of reovirus mRNAs; and (3) To determine the role of the viral nonstructural protein σNS in enhancing the translation of reovirus mRNA in infected cells. Expected outcomes of this work are identification of the viral factors required for compartmentalization of the host translational machinery within viral factories, an understanding of the mechanisms by which reoviruses replicate in the face of ongoing phosphorylated eIF2α and activation of the integrated stress response, and a greater understanding of the role of the reovirus protein σNS in co-opting the host translational machinery and modifying ribosome function. We expect that an important outcome of this proposal will be new basic information regarding viral strategies to overcome innate host defenses.