The role of host and viral translation factors during HCMV infection

性状（由申请方提供）：所有病毒都需要宿主核糖体来合成病毒蛋白。病毒mRNA必须与宿主信息竞争进入宿主翻译机制，因此病毒已经进化出多种机制来确保病毒mRNA在感染期间优先翻译。许多病毒抑制宿主蛋白质合成，可能是为了提供更多的资源用于病毒mRNA的翻译。人巨细胞病毒（HCMV）是不寻常的，因为感染不抑制宿主蛋白质合成。HCMV mRNAs如何有效地与宿主mRNAs竞争进入核糖体？翻译起始因子促进核糖体向mRNA的募集。翻译起始因子的表达和活性的控制是mRNA翻译的关键调控步骤。先前的研究表明，HCMV诱导eIF4F翻译起始复合物的表达和活性，这是加帽mRNA翻译所必需的。由于大多数mRNA都是加帽的，因此大多数宿主mRNA的翻译都需要eIF4F复合物。然而，我们的初步研究表明，令人惊讶的是，抑制控制eIF4F活性的宿主信号传导途径对HCMV mRNA翻译的影响最小。这表明病毒mRNA的翻译起始机制与宿主mRNA的翻译起始机制根本不同。我们的数据表明，HCMV TRS 1蛋白（pTRS 1）作为病毒翻译起始因子，取代病毒mRNA上的eIF4F复合物的功能。这些数据使我们得出了我们的总体假设，即病毒蛋白通过不需要eIF4F复合物的过程指导核糖体加载到HCMV mRNA上。这一假设改变了HCMV mRNA翻译的范式，从宿主蛋白是关键调节因子的范式转变为HCMV蛋白是病毒蛋白合成的主要决定因素的范式。我们在两个特定的目标测试我们的假设。在Aim1中，我们使用遗传学、化学和基因组学方法的组合来确定eIF4F复合物及其亚基在整个感染过程中HCMV mRNA翻译中的作用。目的2验证我们的假设，即pTRS 1是一种病毒翻译起始因子，在病毒mRNA的翻译过程中取代了eIF4F复合物。我们将确定i）pTRS 1如何与翻译机制相关联，ii）感染期间pTRS 1结合的mRNA的完整补体，以及iii）pTRS 1与宿主翻译机制在HCMV mRNA翻译和复制中的相互作用。表

DESCRIPTION (provided by applicant): All viruses share the requirement for host ribosomes for the synthesis of viral proteins. Viral mRNAs must compete with host messages for access to the host translation machinery, and therefore viruses have evolved multiple mechanisms to ensure that viral mRNAs are preferentially translated during infection. Many viruses inhibit host protein synthesis, presumably to provide greater resources for the translation of viral mRNAs. Human cytomegalovirus (HCMV) is unusual in that infection does not inhibit host protein synthesis. How do HCMV mRNAs effectively compete with host mRNAs for access to ribosomes? The recruitment of ribosomes to mRNAs is facilitated by translation initiation factors. Control of translation initiation factor expression and activity is a key regulatory step in mRNA translation. Previous studies have shown that HCMV induces the expression and activity of the eIF4F translation initiation complex, which is required for the translation of capped mRNAs. As most mRNAs are capped, the eIF4F complex is required for the translation of most host mRNAs. However our preliminary studies suggest that, surprisingly, inhibiting host signaling pathways that control eIF4F activity has minimal impact on HCMV mRNA translation. This suggests that the mechanism of translation initiation on viral mRNAs is fundamentally different from that used by host mRNAs. Our data suggests that the HCMV TRS1 protein (pTRS1) acts as a viral translation initiation factor that replaces the function of the eIF4F complex on viral mRNAs. These data lead us to our overall hypothesis that viral proteins direct the loading of ribosomes onto HCMV mRNAs through a process that does not require the eIF4F complex. This hypothesis shifts the paradigm for the translation of HCMV mRNAs, from one in which host proteins are the critical regulatory factors, to one in which HCMV proteins are the primary determinants of viral protein synthesis. We test our hypothesis in two specific aims. In Aim1 we use a combination of genetic, chemical, and genomics approaches to define the role of the eIF4F complex and it subunits in HCMV mRNA translation throughout infection. Aim 2 tests our hypothesis that pTRS1 is a viral translation initiation factor that substitutes for the eIF4F complex during the translation of viral mRNAs. We will determine how i) pTRS1 associates with the translation machinery, ii) the full complement of mRNAs bound by pTRS1 during infection and iii) the role of pTRS1 interaction with the host translation machinery in HCMV mRNA translation and replication. Statement of