Evolution and mechanisms of cytomegalovirus antagonism of host cell defenses

项目摘要/摘要 人巨细胞病毒(HCMV)在免疫系统低下的患者中引起危及生命的疾病 先天性感染新生儿的功能和长期神经功能障碍。除了它的医疗保健 重要性，巨细胞病毒及相关病毒为研究病毒如何 进化成躲避宿主细胞防御系统。这项研究的长期目标是发现进化和 巨细胞病毒等病毒控制宿主细胞蛋白质合成机制的分子机制 病毒复制。蛋白激酶R(PKR)是抑制多种病毒的防御系统之一。 人巨细胞病毒编码PKR的两种蛋白拮抗剂TRS1和IRS1，其中至少有一种是绝对必需的 让病毒在人类细胞中复制。Aim 1试图理解为什么HCMV和其他几个大型DNA一样 病毒有两个基因具有相同的功能。只有一种基因的突变病毒的研究 将用于确定为什么缺少TRS1的病毒具有在缺少病毒的情况下没有观察到的复制缺陷 只有IRS1。其他实验将揭示这两种基因的结合是否对病毒有利。 在比以前的研究更接近模拟自然感染的条件下，例如当临床菌株 人巨细胞病毒感染不同类型的细胞，当它们遇到炎症环境时。目标2将 阐明CMV通过基因复制和水平调节克服PKR的机制 基因转移，这两个过程对大型DNA病毒的进化产生了重大影响。目标3将 剖析PKR中对其活动至关重要的结构域如何适应维持其在 保护宿主，同时做出足够多的改变来躲避病毒因素。这一领域的变体的比较 在人类、东半球的猴子和新大陆的猴子中，使用了强大的“深度突变”技术 扫描一种蛋白质中的每一种氨基酸都突变为所有其他19种氨基酸，将揭示这一现象是如何发生的 PKR的区域已经进化，而CMV又是如何进化来适应变化的。这些研究将 揭示病毒和宿主因素的机制和演变，这些因素处于冲突中， 确定病毒是否可以复制或被主机防御系统成功阻止。

Project Summary/Abstract Human cytomegalovirus (HCMV) causes life-threatening diseases in patients with poor immune system function and long-lasting neurological disabilities in congenitally-infected newborns. In addition to its medical importance, HCMV and related viruses provide a powerful experimental model for investigating how viruses evolve to elude host cell defense systems. The long-term goal of this research is to discover evolutionary and molecular mechanisms by which viruses like HCMV control the host cell's protein synthesis machinery to allow viral replication. One of the defense systems that inhibits many viruses is mediated by protein kinase R (PKR). HCMV encodes two protein antagonists of PKR, TRS1 and IRS1, at least one of which is absolutely essential for the virus to replicate in human cells. Aim 1 seeks to understand why HCMV, like several other large DNA viruses, has two genes that serve the same function. Studies of mutant viruses that have only one of the genes will be used to determine why viruses lacking TRS1 have a replication defect not observed with viruses lacking just IRS1. Other experiments will reveal whether the combination of both genes confers a benefit to the virus under conditions that more closely model natural infections than previous studies, such as when clinical strains of HCMV infect different types of cells, and when they encounter an inflammatory environment. Aim 2 will elucidate mechanisms by which CMV can adapt to overcome PKR using gene duplication and horizontal gene transfer, two processes that have had major impacts on the evolution of large DNA viruses. Aim 3 will dissect how a domain in PKR that is critical for its activity has adapted to maintain its function in defending the host, while changing enough to evade viral factors. Comparisons of variants of this domain in humans, Old World monkeys, and New World monkeys, using the powerful technique of “deep mutational scanning” in which each amino acid in a protein is mutated to all of the other 19 alternatives, will reveal how this region of PKR has evolved and how in turn CMVs have evolved to adapt to the changes. These studies will reveal insights into the mechanisms and evolution of both viral and host factors that are in conflict and that determine whether the virus replicates or is successfully blocked by host defenses.