Cellular Regulation of Papillomavirus E1 Function

描述（由申请人提供）：乳头瘤病毒是皮肤和生殖器疣的病原体。感染某些生殖器乳头瘤病毒亚型是宫颈癌的主要危险因素。目前没有预防性疫苗，也没有持续有效的抗病毒治疗。开发改进的治疗方法需要更深入地了解这些病毒的特性及其与宿主细胞的相互作用。病毒E1蛋白是病毒复制所必需的一种起点结合解旋酶，是潜在治疗干预的一个有吸引力的靶点，因为抑制其功能可以防止病毒复制和繁殖。本研究的长期目标是了解作为真核生物DNA复制模型和治疗靶点的E1蛋白的结构、功能和调控。最近的研究结果表明，E1通过添加SUMO-1片段进行共价修饰。Sumoylation是一种相对较新的细胞修饰系统，可以影响其靶底物的稳定性、细胞内定位和/或活性。E1在一个赖氨酸残基上被聚合，如果这个位点没有聚合，E1的复制功能就会丧失，因为E1不能在细胞核中积累。这些结果表明，sumoylation具有重要的调控功能，控制E1的核定位，并可能调节其他E1的活性。最近，PIAS蛋白（Protein Inhibitors of Activated Stat）被证明与一些底物的SUMO连接酶结合，我们已经证明PIAS1结合E1并刺激瞬时复制。这种复制的刺激是PIAS连接酶活性增强E1聚合化的结果还是PIAS1的其他功能的结果尚不清楚。本研究的具体目标是确定sumo化控制核积累的机制，确定sumo化对E1生化活性的影响，并表征PIAS蛋白对乳头瘤病毒复制和E1 sumo化的影响。这些研究将阐明E1功能的一种新的细胞调控机制，将定义E1的基本核转运途径，并将提供有关趋化作用在宿主细胞核胞质转运中的一般作用的新信息。

DESCRIPTION (provided by applicant): Papillomaviruses are the causative agents of cutaneous and genital warts. Infection with certain subtypes of genital papillomaviruses is the primary risk factor for cervical cancer. Currently there is no preventative vaccine and no consistently effective antiviral therapy. Development of improved treatments will require greater understanding of the properties of these viruses and their interactions with the host cell. The viral E1 protein, an origin-binding helicase essential for viral replication, is an attractive target for potential therapeutic intervention as inhibition of its function should prevent viral replication and propagation. The long-term goal of this research is to understand the structure, function, and regulation of the E1 protein, both as a eukaryotic DNA replication model and as a therapeutic target. Recent results indicate that E1 is covalently modified by addition of a SUMO-1 moiety. Sumoylation is a relatively newly discovered cellular modification system that can affect the stability, intracellular localization, and/or activity of its target substrates. E1 is sumoylated at a single lysine residue, and in the absence of sumoylation at this site E1 replication function is lost because E1 fails to accumulate in the nucleus. These results indicate that sumoylation has an important regulatory function that controls E1 nuclear localization and possibly modulates other E1 activities as well. Recenty, PIAS proteins (Protein Inhibitors of Activated Stat) were shown to SUMO ligases for some substrates, and we have shown the PIAS1 binds E1 and stimulates transient replication. Whether or not this stimulation of replication is the result of PIAS ligase activity enhancing E1 sumoylation or some other function of PIAS1 is unknown. The specific goals of this proposal are to ascertain the mechanism by which sumoylation controls nuclear accumulation, determine the consequences of sumoylation on E1 biochemical activities, and characterize the effect of PIAS proteins on papillomavirus replication and E1 sumoylation. These studies will elucidate a novel cellular regulatory mechanism for E1 function, will define the basic nuclear transport pathway(s) for E1, and will also provide new information about the general role that sumoylation plays in host cell nucleocytoplasmic transport.