Epstein-Barr virus (EBV) infection and lytic replication are known to induce a cellular DNA damage response. We previously showed that the virally encoded BPLF1 protein interacts with and regulates several members of the translesion synthesis (TLS) pathway, a DNA damage tolerance pathway, and that these cellular factors enhance viral infectivity. BPLF1 is a late lytic cycle gene, but the protein is also packaged in the viral tegument, indicating that BPLF1 may function both early and late during infection. The BPLF1 protein expresses deubiquitinating activity that is strictly conserved across the Herpesviridae; mutation of the active site cysteine results in a loss of enzymatic activity. Infection with an EBV BPLF1 knockout virus results in decreased EBV infectivity. Polymerase eta (Pol η), a specialized DNA repair polymerase, functions in TLS and allows for DNA replication complexes to bypass lesions in DNA. Here we report that BPLF1 interacts with Pol η and that Pol η protein levels are increased in the presence of functional BPLF1. BPLF1 promotes a nuclear relocalization of Pol η molecules which are focus-like in appearance, consistent with the localization observed when Pol η is recruited to sites of DNA damage. Knockdown of Pol η resulted in decreased production of infectious virus, and further, Pol η was found to bind to EBV DNA, suggesting that it may allow for bypass of damaged viral DNA during its replication. The results suggest a mechanism by which EBV recruits cellular repair factors, such as Pol η, to sites of viral DNA damage via BPLF1, thereby allowing for efficient viral DNA replication.

IMPORTANCE Epstein-Barr virus is the causative agent of infectious mononucleosis and infects approximately 90% of the world's population. It causes lymphomas in individuals with acquired and innate immune disorders and is strongly associated with Hodgkin's lymphoma, Burkitt's lymphoma, diffuse large B-cell lymphomas, nasopharyngeal carcinoma (NPC), and lymphomas that develop in organ transplant recipients. Cellular DNA damage is a major determinant in the establishment of oncogenic processes and is well studied, but there are few studies of endogenous repair of viral DNA. This work evaluates how EBV's BPLF1 protein and its conserved deubiquitinating activity regulate the cellular DNA repair enzyme polymerase eta and recruit it to potential sites of viral damage and replication, resulting in enhanced production of infectious virus. These findings help to establish how EBV enlists and manipulates cellular DNA repair factors during the viral lytic cycle, contributing to efficient infectious virion production.

已知爱泼斯坦巴尔病毒（EBV）感染和裂解复制可诱导细胞DNA损伤反应。我们以前显示病毒编码的BPLF1蛋白与跨病变合成（TLS）途径（DNA损伤耐受途径）的几个成员相互作用并对其进行调节，并且这些细胞因子增强了病毒的感染性。BPLF1是一个晚期裂解周期基因，但该蛋白也包装在病毒皮中，表明BPLF1可能在感染过程的早期和晚期起作用。BPLF1蛋白表达去泛素化活性，在整个疱疹病毒科中严格保守; 活性位点半胱氨酸的突变导致酶活性的损失。用EBV BPLF1基因敲除病毒感染会导致EBV感染力降低。聚合酶η（Polη）是一种特殊的DNA修复聚合酶，在TLS中起作用，并允许DNA复制复合物绕过DNA中的损伤。在这里，我们报告BPLF1与Polη相互作用，并且在存在功能性BPLF1的情况下Polη蛋白水平升高。BPLF1促进外观上像焦点的Polη分子的核再定位，这与将Polη募集到DNA损伤位点时观察到的定位一致。敲低Polη会导致感染性病毒的产生减少，此外，还发现Polη与EBV DNA结合，这表明它可以在复制过程中绕过受损的病毒DNA。

重要性爱泼斯坦-巴尔病毒是传染性单核细胞增多症的病原体，感染了全世界约90％的人口。它在患有获得性和先天性免疫疾病的个体中引起淋巴瘤，并与霍奇金淋巴瘤，伯基特淋巴瘤，弥漫性大B细胞淋巴瘤，鼻咽癌（NPC）和器官移植受者中发展的淋巴瘤密切相关。细胞DNA损伤是建立致癌过程的主要决定因素，并且已经得到充分研究，但是对病毒DNA内源性修复的研究很少。这项工作评估了EBV的BPLF1蛋白及其保守的去泛素化活性如何调节细胞DNA修复酶聚合酶eta，并将其募集到潜在的病毒损伤和复制位点，从而提高了传染性病毒的产量。