EB病毒致瘤蛋白LMP1通过泛素信号整合调节p53的稳定性

项目名称： EB病毒致瘤蛋白LMP1通过泛素信号整合调节p53的稳定性

项目编号： No.30801337

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 李力力

作者单位： 中南大学

项目金额： 21万元

中文摘要： 本项目以鼻咽癌为切入点，结合当今生命科学研究的热点和前沿-泛素化和甲基化，探讨EBV致瘤蛋白LMP1通过泛素信号通路和表观遗传异常调节p53 稳定性的分子机制和生物学功能。在前期研究的基础上，采用p53-野生型和p53-null的细胞模型发现，EBV LMP1能同时上调p53和MDM2蛋白水平的表达，及延长其半衰期，但增加p53的泛素化。LMP1主要通过TARF2介导p53 UbK63位的泛素化进而促进p53稳定性的增加。功能研究表明，EBV LMP1通过抑制p53介导的G1/S和G2/M细胞周期阻滞和凋亡，从而维持鼻咽癌的潜伏感染。以前期筛选出的、在鼻咽癌中表达显著下调的UCHL1为切入点，甲基化分析表明在鼻咽癌细胞和肿瘤组织中UCHL1启动子普遍受甲基化的调控，可作为潜在的鼻咽癌分子标志物。UCHL1通过与p53/MDM2/ARF形成复合物，参与调节p53的去泛素化进一步活化p53信号通路，从而促进鼻咽癌细胞的生长抑制和凋亡。本项目首次从泛素化和表观遗传角度阐明p53在病毒致瘤相关疾病中的重要作用，为理解p53 的生物学意义提供重要的实验依据。

中文关键词： EBV；LMP1；p53；泛素化；甲基化

英文摘要： The funded project aims to study molecular mechanisms of p53 accumulation/stability through ubiquitin-signaling pathway and epigenetic disruption by Epstein-Barr virus (EBV) encoded latent memebrane protein 1 (LMP1).Using p53-wild type and p53-null cell models, we found that EBV LMP1 upregulated both p53 and MDM2 protein levels, which arrtributed to the extendence of p53 and MDM2 half-life, but increased the ubiquitination of p53. EBV LMP1 abrogated p53-induced G1/S and G2/M cell cycle arrest and apoptosis, conferring to the maintainance of latent infectinon of nasopharyngeal carcinoma (NPC). We found that UCHL1 is downregulated/silenced in NPC tumor cell lines, but not in normal upper respiratory tract tissues and immmortalized cell line. Promoter CpG methylation of UCHL1 is frequently detected in NPC tumor cell lines and primary tumors,but rarely detected in immortalized nasopharyngeal cells and normal nasopharyngeal tissues, suggesting the potential of UCHL1 as epigenetic biomarker in NPC. Furthermore, we found that UCHL1 could deubiquitinate p53 and p14ARF and ubiquitinate MDM2 through forming a complex with p53/p14ARF/MDM2, resulting in p53 stabilization and the activation of p53 signaling, thus involved in NPC pathogenesis. This proposed project elucidates the critical role of p53 in virus-related maliganancies from both ubiquitination and methylation aspects, which will help us to understand the biologicial significance of p53 in virus-induced tumorigenesis.

英文关键词： Epistein-Barr virus; LMP1; p53; ubiquitination; methylation