Virus Evolution Through Horizontal Gene Transfer

项目摘要 水平基因转移（Horizontal gene transfer，HGT）是一种重要的生物学现象 但在病毒进化的背景下，其潜在的机制和后果远没有那么好- 明白痘病毒和其他大型DNA病毒编码许多明确的细胞起源的基因。我的目标是 调查他们是如何到达那里并在收购后发展的。我们已经证明LINE-1（L1） 逆转录转座子在将细胞基因转移到痘病毒基因组中起关键作用， 了解这是如何发生的动力学，而不诱导灾难性的插入突变。多新 获得性基因进化出前病毒功能，并避免由于其细胞内的功能冗余而导致的缺失。 祖该建议的中心假设是痘病毒基因组中的L1插入富集了 基因组的远端区域，避免破坏必要的核心基因，在那里它们可以进化以造福人类。 病毒我将集中讨论从这一假设中出现的两个主要的悬而未决的问题。目标1我会 表征病毒复制和细胞L1机制之间的相互作用。这将在空间上包括 定义细胞质内的相互作用，了解L1活性是否以及如何影响病毒复制， 全面表征L1介导的插入到病毒基因组中的频率和分布。 为了做到这一点，我将结合实验和计算技术，跨越分子生物学， 生物化学、遗传学和下一代测序。在目标2中，我将试图阐明 痘病毒K3 L的进化，一种抗病毒效应PKR的宿主衍生抑制剂。K3 L是一种结构同源物， 竞争性抑制PKR诱导的翻译关闭。与eIF 2相比， 显著截短且缺乏磷酸化位点，因此不能介导抗病毒功能 PKR下游。尽管有这种同源性，计算和系统发育分析表明K3 L是最常见的。 与产甲烷古菌的aIF 2 α蛋白密切相关，可能不是从宿主获得的 痘病毒起源于痘病毒祖先的细胞，而是来自占据相似或重叠生态空间的微生物。以来 我的原始提交，我已经产生了新的初步数据，M。fervens aIF 2 β抑制脊椎动物PKR， 为我的计算工作提供实验支持。我将确认并扩展这些结果， 哺乳动物细胞培养，并使用实验进化来模拟新获得的病毒基因的适应。 最近在其他DNA病毒中发现的古细菌起源基因，为我的研究提供了进一步的支持。 假设，但K3 L将是第一个已知的例子，在病毒的多细胞真核生物。一图 病毒作为不同基因交换节点的大熔炉的出现，我提出的研究将 阐明了一个新的病毒家族在这些生态空间中的参与。这些研究将进一步 我们对细胞基因的病毒共选择过程的理解以及探索意想不到的 病毒遗传多样性的机制及其所占据的生态空间。

Project Summary Horizontal gene transfer (HGT) is a well characterized phenomenon driving the evolution and genetic diversity of bacteria but its underlying mechanisms and consequences in the context of viral evolution are far less well- understood. Poxviruses and other large DNA viruses encode numerous genes of clear cellular origin. I aim to investigate how they get there and evolve following their acquisition. We have demonstrated that LINE-1 (L1) retrotransposons play a key role in the transfer of cellular genes into poxvirus genomes but do not yet understand the dynamics of how this occurs without inducing catastrophic insertional mutagenesis. How newly acquired genes evolve proviral functions and avoid deletion due to functional redundancy with their cellular ancestor. The central hypothesis of this proposal is that L1 insertions into poxvirus genomes are enriched in distal regions of the genome, avoiding disruption of essential core genes, where they can evolve to benefit the virus. I will focus on two major outstanding questions emerging from this hypothesis. In Aim 1 I will characterize the interaction between virus replication and cellular L1 machinery. This will comprise spatially defining the interaction within the cytoplasm, understanding if and how L1 activity impacts viral replication, and comprehensively characterizing the frequency and distribution of L1-mediated insertions into the viral genome. To do so I will use a combination of experimental and computational techniques spanning molecular biology, biochemistry, genetics, and next-generation sequencing. In Aim 2 I will seek to elucidate the origin and evolution of poxvirus K3L, a host-derived inhibitor of the antiviral effector PKR. K3L is a structural homolog of vertebrate eIF2 that competitively inhibits PKR-induced translational shutoff. Compared to eIF2 K3L is dramatically truncated and lacks a phosphorylation site, and so cannot mediate the antiviral functions downstream of PKR. Despite this homology, computational and phylogenetic analysis suggests K3L is most closely related to the aIF2 protein of methanogenic archaea and may not have been acquired from the host cell of an ancestral poxvirus but rather from microbes occupying similar or overlapping ecological space. Since my original submission, I have generated new preliminary data that M. fervens aIF2 inhibits vertebrate PKR, giving experimental support to my computational work. I will confirm and expand on these results in mammalian cell culture, and use experimental evolution to model the adaptation of newly acquired viral genes. The recent identification of archaeal-origin genes in other DNA viruses, provides further support for my hypothesis, but K3L would be the first known example in viruses of multicellular eukaryotes. A picture is emerging of viruses as melting pots in nodes of diverse genetic exchange and my proposed studies will illuminate the participation of a new family of viruses in these ecological spaces. These studies will advance our understanding of the process of viral co-option of cellular genes as well as explore unexpected mechanisms underlying the genetic diversity of viruses and the ecological spaces they occupy.