Mechanisms of Gene Regulation by EBV EBNA-1 Protein

几乎没有明显疾病hinc B淋巴细胞。然而，免疫监视的崩溃，例如，作为 艾滋病的后果，仍然是发展EBV相关淋巴瘤的重要危险因素， 强调了这种潜在致癌疱疹病毒和 宿主免疫系统这种平衡依赖于EB病毒潜伏相关基因的选择性下调。 在建立持续感染期间的基因表达，最终限制病毒基因的表达 对于维持持久性至关重要，同时排除那些具有急性转化特性和/或 编码由EBV特异性T细胞监视识别的显性表位。这一过程中的一个关键过程 向限制性潜伏期的转变是启动子转换事件，其使得能够排他性地表达必需的 EBV基因组维持蛋白EBNA-1，来自启动子Qp，其可以通过以下途径负调控： 两个EBNA-1结合位点紧邻其转录起始位点下游。我们最近努力定义 EBNA-1抑制的机制揭示了它不是通过抑制转录而起作用，如最初所认为的， 而是通过抑制前体mRNA的加工。此外，这种自动调节的主要意义在于， 最近变得明显。尽管EBNA-1早期被认为是宿主免疫系统不可见的， 由于其顺式抑制其被细胞蛋白酶体降解的能力， 阻止与HLA I类分子相关的EBNA-1肽表位的呈递，随后 研究表明，识别EBNA-1的细胞毒性T细胞不仅存在，而且它们被导向 在EBNA-1的实际合成过程中产生的肽，而不是通过成熟EBNA-1的降解产生的肽。因此，在本发明中， 对蛋白酶体降解的抗性是次要的，EBNA-1的自调节表达是主要的， EBV限制EBNA-1特异性T细胞杀伤的机制。此外，最近描述的抗细胞凋亡 EBNA-1的特性表明它可能具有致瘤潜力。因此，我们假设， EBNA-1的自身调节功能对于EBV持续存在及其相关的致病性是非常关键的， 潜力：它确保足够的EBNA-1用于基因组维持，同时限制EBNA-1合成低于 如果超过该阈值，潜伏感染的B细胞将被EBNA-1特异性细胞毒性T细胞消除 细胞和潜在的致癌转化。我们提出了三个具体目标，以帮助我们实现我们的长期目标。 目的是确定EBNA-1自身调节对EBV生物学、免疫逃避和免疫应答的贡献。 发病机制：1）明确EBNA-1自身调节机制; 2）阐明EBNA-1的作用 对潜伏期的增长和限制程序的自动调节;和3）定义Qp和 Fp，一种替代的邻近EBNA-1启动子，在EBV感染中。

hin B lymphocytes with little overt disease. However, a breakdown in immune surveillance, e.g., as a consequence of AIDS, remains a significant risk factor for development of EBV-associated lymphoma, underscoring the highly evolved equilibrium that exists between this potentially oncogenic herpesvirus and the host immune system. This equilibrium is dependent on a selective down-regulation of EBV latency-associated gene expression during establishment of persistent infection that ultimately restricts expression to viral genes critical for maintenance of persistence, while precluding those with acute transforming properties and/or which encode dominant epitopes recognized by the EBV-specific T-cell surveillance. A pivotal process in this transition to restricted latency is a promoter switching event that enables exclusive expression of the essential EBV genome-maintenance protein, EBNA-1, from the promoter Qp, which can be negatively regulated through two EBNA-1 binding sites immediately downstream of its transcription start site. Our recent efforts to define the mechanism of EBNA-1 repression revealed that it acts not by inhibition of transcription, as originally believed, but by suppression of pre-mRNA processing. The principal significance of this autoregulation, furthermore, has recently become apparent. Although EBNA-1 was earlier thought to be ¿invisible¿ to the host immune surveillance as a consequence of its ability to inhibit in cis its degradation by the cell proteasome, thereby preventing presentation of EBNA-1 peptide epitopes in association with HLA class I molecules, subsequent studies indicated that cytotoxic T cells that recognize EBNA-1 not only exist, but that they are directed towards peptides generated during actual synthesis of EBNA-1, not by the degradation of mature EBNA-1. Thus, resistance to proteasomal degradation is secondary to the autoregulated expression of EBNA-1 as the primary mechanism employed by EBV to restrict EBNA-1-specific T-cell killing. Further, recently described antiapoptotic properties of EBNA-1 suggest that it may have tumorigenic potential. We hypothesize, therefore, that the autoregulatory function of EBNA-1 is highly critical to EBV persistence and its associated pathogenic potential: it ensures sufficient EBNA-1 for genome maintenance, while limiting EBNA-1 synthesis below a threshold that, if exceeded, would subject latently infected B cells to elimination by EBNA-1-specific cytotoxic T cells, and potentially oncogenic transformation. We propose three specific aims to help us reach our long-term objective of defining the contribution of EBNA-1 autoregulation to EBV biology, immune evasion and pathogenesis: 1) Define the mechanism of EBNA-1 autoregulation; 2) Elucidate the contributions of EBNA-1 autoregulation to the growth and restricted programs of latency; and 3) Define the respective roles of Qp and Fp, an alternative adjacent EBNA-1 promoter, in EBV infection.