EBV's Plasmid Replicon: Its Synthesis, Partitioning, and Maintenance of Tumors

描述(申请人提供)：爱泼斯坦-巴尔病毒(EBV)是一种人类肿瘤病毒，与多种类型的淋巴瘤和癌症有关。它的基因组在正常和恶性增殖细胞中都以质粒的形式存在。我们研究了EBV的质粒型复制子，以阐明其合成和分配及其在EBV肿瘤发生中的作用。早些时候，我们鉴定了它的顺式作用元件ORIP和它唯一的病毒反式作用蛋白EBNA1。我们最近开发了一种在活细胞中可视化EBV质粒复制子的方法，该方法揭示了几个有趣的特性。例如，它们在每个S阶段只有84%的时间被复制；它们编码了一种非随机的分割机制，这种机制在空间上将分割与它们的合成相结合。现在，我们在目标1中建议在原代B细胞感染后早期表征EBV基因组的合成和分割，以了解这些事件如何有助于EBV建立其对这些细胞的稳定感染。在目标2中，我们将剖析EBV的分离机制，以了解其与其合成的耦合。我们最近还发现，通过抑制EBNA1来抑制EBV的质粒复制子可以诱导正常和恶性的EBV感染的B细胞凋亡。我们将在目标3中将这些发现扩展到免疫受损宿主中的EBV相关肿瘤，如艾滋病患者。特别是，我们建议研究EBV阻止这些感染的、恶性的B细胞凋亡的机制，并确定允许这些肿瘤细胞存活的病毒基因。 与公共卫生相关：所有这些研究都将揭示EBV在感染细胞中以质粒形式复制的机制。除了指出抑制EBNA1将如何在治疗上有益外，他们还应该确定开发抗病毒抗肿瘤药物的额外靶点。

DESCRIPTION (provided by applicant): Epstein-Barr Virus (EBV) is a human tumor virus causally associated with multiple types of lymphomas and carcinomas. Its genome is maintained in both normal and malignant proliferating cells as a plasmid. We have studied EBV's plasmid replicon to elucidate both its synthesis and partitioning and its contributions to EBV's tumorigenesis. Earlier we identified its cis-acting element, oriP, and its sole viral trans-acting protein, EBNA1. We recently developed a method to visualize EBV plasmid replicons in live cells, which has uncovered several fascinating properties. For example, they are duplicated each S-phase only 84% of the time; and they encode a non-random mechanism of partitioning which spatially couples partitioning to their synthesis. We propose now in Aim 1 to characterize the synthesis and partitioning of EBV genomes early after infection of primary B-cells to understand how these events contribute to EBV's establishing its stable infection of these cells. We shall in Aim 2 dissect the mechanism of EBV's partitioning to understand its coupling to its synthesis. We have also recently discovered that inhibiting EBV's plasmid replicon by inhibiting EBNA1 induces apoptosis in normal and malignant, EBV-infected B-cells. We shall extend these findings in Aim 3 to EBV-associated tumors in immunocompromised hosts such as AIDS patients. In particular, we propose to investigate the mechanisms by which EBV prevents apoptosis in these infected, malignant B-cells and identify the viral genes that allow these tumor cells to survive. PUBLIC HEALTH RELEVANCE: All of these studies will reveal the mechanisms by which EBV replicates as a plasmid in infected cells. In addition to indicating how inhibiting EBNA1 would be therapeutically beneficial, they should also identify additional targets for developing anti-viral anti-tumor drugs.