CELLULAR AND VIRAL REGULATION OF TYPE III EBV LATENCY

EBV作为人类肿瘤病毒的特征是其使B淋巴细胞永生化并建立不同程度的潜伏期的能力。EBV潜伏产物调节细胞周期进程中重要的细胞信号传导途径。在这里，我们提出，细胞信号分子调节EBV产品的表达在细胞周期依赖性的方式。EBNA-2是III型潜伏期中使用的所有启动子的主要调节因子。我们发现EBNA-2在细胞周期的M期特异性过度磷酸化，这与III型胶原的抑制有关。 促进活动。这些观察结果表明，在有丝分裂中可能存在EBNA-2的反式激活功能的普遍抑制。在目的I中，我们研究了在细胞周期中与EBNA-2磷酸化状态相关的III型潜伏产物的调节。我们已经暗示p34/cdc 2激酶在M期EBNA-2过度磷酸化，并确定了EBNA-2特异性磷酸化位点。我们将确定该位点的生物学作用，并通过突变分析确定M期EBNA-2磷酸化的其他位点。EBV感染影响重要的细胞信号传导途径。最近，我们发现EB病毒诱导β-连环蛋白/Tcf通路，一个关键的细胞致癌途径，在III型潜伏期。在目的II中，我们研究了潜伏的EBV感染状态如何严重改变这一途径，并将研究它是否是EBV永生化B细胞所必需的。我们将研究是否抑制这一途径导致生长停滞和分化的EBV永生化B淋巴细胞。最后，在Aim III中，基于其他发现，即去泛素化和泛素化参与β-连环蛋白的稳定，我们将把这些病毒和细胞 它们可能参与EBV的致癌机制。具体来说，我们将剖析β-连环蛋白在III型潜伏期中的稳定机制，重点是EBNA-2在去泛素化中的作用，以及LMP-1在泛素化中的作用。这两个关键蛋白酶体调节过程之间的平衡失调可能是肿瘤病毒调节宿主细胞信号传导途径的普遍现象。

Characteristic of EBV as a human tumor virus is its ability to immortalize B-lymphocytes and establish different degrees of latency. EBV latency products regulate cell-signaling pathways important in cell-cycle progression. Here we propose that cell-signaling molecules regulate the expression of EBV products in a cell-cycle-dependent manner. EBNA-2 is the master regulator of all the promoters used in Type III latency. We show that EBNA-2 is specifically hyperphosphorylated in M phase of the cell cycle, which correlates with suppression of Type III promoter activities. These observations indicate that there may be general inhibition of EBNA-2's transactivation functions in mitosis. In Aim I we examine regulation of type III latency products during the cell cycle in relation to EBNA-2 phosphorylation status. We have implicated p34/cdc2 kinase in EBNA-2 hyperphosphorylation during M phase and identified a phosphorylation site of EBNA-2 specific for this kinase. We will determine the biological role of this site and also identify other sites of EBNA-2 phosphorylation in M phase through mutational analysis. EBV infection affects important cell-signaling pathways. Recently we discovered that EBV induces the beta-catenin/Tcf pathway, a key cellular oncogenic pathway, in type III latency. In Aim II we examine how the latent EBV infection state critically alters this pathway and will investigate whether it is essential for immortalization of B-cells by EBV. We will examine if inhibition of this pathway leads to growth arrest and differentiation in EBV-immortalized B-lymphocytes. Finally, in Aim III, based on other discoveries, namely, involvement of both deubiquitination and ubiquitination in beta-catenin stabilization, we will bring together these viral and cellular mechanisms, since they are likely to be involved in EBV oncogenesis. Specifically, we will dissect the mechanism of beta-catenin stabilization in type III latency, focusing on the role of EBNA-2 in deubiquitination, and LMP-1 in ubiquitination. Dysregulation of the balance between these two key proteasomal regulatory processes is likely to be a general phenomenon whereby tumor viruses modulate signaling pathways of host cells.