Uracil DNA glycosylases in herpesvirus pathogenesis and DNA mutation

描述（由申请人提供）：尿嘧啶DNA糖基化酶（UNG）是一种去除错误合并和致突变尿嘧啶的酶，留下一个通常由宿主碱基切除修复途径修复的基本位点。每种疱疹病毒都编码一个病毒UNG，但我们对这个高度保守的基因在病毒生命周期中的功能知之甚少。研究表明，疱疹病毒的vUNGs与病毒DNA复制机制的组成部分相互作用，并促进原代或静止细胞的后期复制事件。据报道，单纯疱疹病毒的vUNG可增强小鼠的单纯疱疹病毒潜伏期，但vUNG在自然宿主γ疱疹病毒感染的整个致病过程中所起的作用尚未报道。γ疱疹病毒爱泼斯坦-巴尔病毒、卡波西肉瘤相关疱疹病毒和小鼠模型病原体小鼠γ疱疹病毒68在免疫球蛋白类转换的B细胞中建立潜伏期；感染可导致B细胞的永生化和转化。宿主UNG2活性是产生B细胞多种抗体库所必需的，但也会引发染色体易位，这是淋巴瘤的病因。因此，尿嘧啶糖苷酶活性的改变可能会打破免疫和恶性肿瘤之间的平衡。本研究旨在了解伽玛疱疹病毒编码的UNGs如何促进病毒的发病机制，并影响宿主的B细胞抗体库和淋巴瘤发生。在Aim 1中，将确定病毒和宿主UNG在裂解复制过程中对促进病毒基因组完整性的影响。此外，我们将研究在宿主UNG2存在或不存在的情况下MHV68 - vUNG发病机制的变化，以确定病毒和宿主UNG对体内复制、潜伏期和再激活的贡献。在Aim 2中，我们将讨论病毒性UNG是否促进致突变结果，如免疫球蛋白基因类别开关重组和体细胞超突变，癌基因脱靶突变，或易位，如定义EBV+伯基特淋巴瘤的c-myc/Ig易位。我们的研究可能会揭示病毒UNG与宿主胞苷脱氨酶AID的相互作用，这将为HV癌症的分子病因学提供重要的见解。

DESCRIPTION (provided by applicant): Uracil DNA glycosylase (UNG) is an enzyme that removes misincorporated and mutagenic uracils, leaving an abasic site typically repaired by the host base excision repair pathway. Each herpesvirus encodes a viral UNG, but we know little regarding the function of this highly conserved gene in the virus lifecycle. Studies indicate that herpesvirus vUNGs interact with components of the viral DNA replication machinery and promote late stage replication events in primary or quiescent cells. The vUNG of herpes simplex virus has been reported to enhance herpes simplex virus latency in mice, but the role of vUNG in a full pathogenic course of gammaherpesvirus infection in a natural host has not been reported. The gammaherpesviruses Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, and the mouse model pathogen murine gammaherpesvirus 68 establish latency in immunoglobulin class-switched B cells; infection can lead to immortalization and transformation of B cells. Host UNG2 activity is required for generating the diverse antibody repertoire of B cells, but also triggers chromosome translocations that are the etiology of lymphomas. Thus, alterations of uracil glycoslyase activity may tip the balance between immunity and malignancy. This proposal is to understand how the UNGs encoded by the gammaherpesviruses promote viral pathogenesis and impact the B cell antibody repertoire and lymphomagenesis of the host. In Aim 1, the impact of viral and host UNG on promoting the integrity of the viral genome in the process of lytic replication will be determined. In addition, we will examine changes in the pathogenesis of MHV68¿vUNG in the presence or absence of host UNG2 to determine the contribution of viral and host UNG to replication, latency, and reactivation in vivo. In Aim 2, we will address whether viral UNG promotes mutagenic outcomes such as immunoglobulin gene class-switch recombination and somatic hypermutation, off-target mutations in oncogenes, or translocations such as c-myc/Ig translocations that define EBV+ Burkitt's lymphoma. Our studies might uncover an interaction of viral UNG with the host cytidine deaminase AID that will provide critical insight regarding the molecular etiology of ¿HV cancers.