Defining mechanisms of gammaherpesvirus-driven genomic instability in B cells

项目摘要 γ-疱疹病毒（GHV）建立终身慢性感染，使宿主处于许多疾病的危险之中。 癌的在慢性感染过程中，GHV表达病毒基因产物，刺激宿主细胞增殖， 分化，被认为是促进长期潜伏持续并有助于肿瘤发生的过程。 然而，GHV并不是急性转化的，并且由于GHV的高感染率，癌症是罕见的。 成年人，估计超过95%的EB病毒（EBV）。这表明宿主细胞是 具有对GHV驱动的增殖和细胞永生化的内在抗性。在完成的工作中 在上一个资助期间，我们确定了肿瘤抑制因子p53作为一种蛋白质， GHV潜伏感染的建立。p53通常被认为是“基因组的守护者”， 多个诱变途径的下游，以阻止细胞周期进程，刺激DNA修复，或促进 凋亡p53在人类癌症中经常发生突变，包括地方性伯基特淋巴瘤，一种与EBV相关的 以免疫球蛋白重链之间的染色体易位为特征的淋巴瘤 启动子和细胞原癌基因c-myc。据推测，EBV与疟疾协同作用，以促进 携带IgH/c-myc易位的细胞的存活。使用鼠γ疱疹病毒68（MHV 68）感染 小鼠作为小动物模型，使多系统分析GHV发病机制，我们证明， p53限制细胞增殖，特别是生殖中心（GC）细胞的增殖。我们还发现p53抑制IgH/c- 感染小鼠B细胞中myc易位，与增强型B细胞淋巴瘤相关 在用MHV 68感染的p53缺陷小鼠中的发育。此外，我们提供的初步数据表明， 用MHV 68和鼠疟疾寄生虫共感染小鼠也促进IgH/c-myc易位。 在这种竞争性的更新中提出的实验将建立在我们以前的进展基础上，利用强大的 小鼠和MHV 68遗传系统，以（i）确定促进基因组的病毒基因和分子途径 不稳定性和淋巴瘤发展，（ii）鉴定GHV驱动淋巴瘤中病毒和宿主因子依赖性， 和（iii）确定MHV 68和鼠疟原虫寄生虫促进 染色体易位除了更好地了解GHV如何引起疾病外，我们 预计这项工作的结果将为针对淋巴瘤依赖性的新治疗方法提供信息 并降低GHV和相关合并感染的致突变潜力。

PROJECT SUMMARY Gammaherpesviruses (GHVs) establish lifelong chronic infections that place the host at risk for numerous cancers. During chronic infection, GHVs express viral gene products that stimulate host-cell proliferation and differentiation, processes thought to facilitate long-term latent persistence and contribute to tumorigenesis. However, GHVs are not acutely transforming, and cancer is rare given the high incidence of infection among adult humans, estimated at more than 95% for Epstein-Barr virus (EBV). This suggests that host cells are equipped with an intrinsic resistance to GHV-driven proliferation and cellular immortalization. In work performed during the previous funding period, we identified the tumor suppressor p53 as a protein that is activated during the establishment of GHV latent infection. p53 is frequently considered a “guardian of the genome”, working downstream of multiple mutagenic pathways to halt cell-cycle progression, stimulate DNA repair, or promote apoptosis. p53 is frequently mutated in human cancers, including endemic Burkitt lymphoma, an EBV-associated lymphoma that is characterized by a chromosomal translocation between the immunoglobulin heavy-chain promoter and cellular proto-oncogene c-myc. It is hypothesized that EBV synergizes with malaria, to promote the survival of cells that harbor IgH/c-myc translocations. Using murine gammaherpesvirus 68 (MHV68) infection of mice as a small animal model to enable a multi-system analysis GHV pathogenesis, we demonstrated that p53 limits cellular proliferation, especially of germinal center (GC) cells. We also found that p53 inhibits IgH/c- myc translocations in B cells of infected mice, an event that correlates with enhanced B cell lymphoma development in p53-deficient mice infected with MHV68. Moreover, we provide preliminary data indicating that co-infection of mice with MHV68 and a murine malaria parasite also promotes IgH/c-myc translocations. Experiments proposed in this competing renewal will build on our previous progress, harnessing the powerful mouse and MHV68 genetic systems, to (i) define viral genes and molecular pathways that promote genomic instability and lymphoma development, (ii) identify viral and host-factor dependencies in GHV-driven lymphomas, and (iii) determine the mechanisms through which MHV68 and murine Plasmodium parasites facilitate chromosomal translocations. In addition to providing a better understanding of how GHVs cause disease, we anticipate that results of this work will inform new therapeutic approaches that target lymphoma dependencies and reduce the mutagenic potential of GHVs and related co-infections.