Evolution and mechanisms of cytomegalovirus antagonism of host cell defenses

项目总结/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。除了医疗 重要的是，HCMV和相关病毒提供了一个强大的实验模型，用于研究病毒如何 进化以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 HCMV等病毒控制宿主细胞蛋白质合成机制的分子机制， 病毒复制抑制许多病毒的防御系统之一是由蛋白激酶R（PKR）介导的。 HCMV编码两种PKR拮抗蛋白TRS 1和IRS 1，其中至少一种是必不可少的 让病毒在人体细胞中复制目的1试图理解为什么HCMV，像其他几个大的DNA 病毒，有两个基因，具有相同的功能。研究只有一个基因的突变病毒 将用于确定为什么缺乏TRS 1的病毒具有复制缺陷，而缺乏TRS 1的病毒没有观察到复制缺陷。 只有IRS 1。其他实验将揭示这两种基因的结合是否会给病毒带来好处 在比以前的研究更接近自然感染模型的条件下，例如当临床菌株 HCMV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可以利用基因复制和水平表达来适应克服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中对其活性至关重要的结构域如何适应以维持其功能， 保护宿主，同时改变足以逃避病毒因素。此域的变体的比较 在人类、旧世界猴子和新世界猴子中，使用强大的“深度突变”技术， 蛋白质中的每一个氨基酸都突变为其他19种替代品，这将揭示这种突变是如何发生的。 PKR区域已经演变，以及CMV如何演变以适应变化。这些研究将 揭示了病毒和宿主因素相互冲突的机制和演变， 确定病毒是否复制或是否被主机防御成功阻止。

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.