Silla Toomas, Hääl Ingrid, Geimanen Jelizaveta, Janikson Kadri, Abroi Aare, Ustav Ene, Ustav Mart
Department of Microbiology and Virology, Institute of Molecular and Cell Biology, Tartu University, Riia 23 St., Tartu 51010, Estonia.
J Virol. 2005 Dec;79(24):15277-88. doi: 10.1128/JVI.79.24.15277-15288.2005.
Bovine papillomavirus type 1 (BPV1), Epstein-Barr virus (EBV), and human herpesvirus 8 genomes are stably maintained as episomes in dividing host cells during latent infection. The mitotic segregation/partitioning function of these episomes is dependent on single viral protein with specific DNA-binding activity and its multimeric binding sites in the viral genome. In this study we show that, in the presence of all essential viral trans factors, the segregation/partitioning elements from both BPV1 and EBV can provide the stable maintenance function to the mouse polyomavirus (PyV) core origin plasmids but fail to do so in the case of complete PyV origin. Our study is the first which follows BPV1 E2- and minichromosome maintenance element (MME)-dependent stable maintenance function with heterologous replication origins. In mouse fibroblast cell lines expressing PyV large T antigen (LT) and either BPV1 E2 or EBV EBNA1, the long-term episomal replication of plasmids carrying the PyV minimal origin together with the MME or family of repeats (FR) element can be monitored easily for 1 month under nonselective conditions. Our data demonstrate clearly that the PyV LT-dependent replication function and the segregation/partitioning function of the BPV1 or EBV are compatible in certain, but not all, configurations. The quantitative analysis indicates a loss rate of 6% per cell, doubling in the case of MME-dependent plasmids, and 13% in the case of FR-dependent plasmids in nonselective conditions. Our data clearly indicate that maintenance functions from different viruses are principally interexchangeable and can provide a segregation/partitioning function to different heterologous origins in a variety of cells.
1型牛乳头瘤病毒（BPV1）、爱泼斯坦-巴尔病毒（EBV）和人类疱疹病毒8型基因组在潜伏感染期间以附加体形式稳定维持于分裂的宿主细胞中。这些附加体的有丝分裂分离/分配功能依赖于具有特定DNA结合活性的单一病毒蛋白及其在病毒基因组中的多聚体结合位点。在本研究中，我们发现，在所有必需的病毒反式因子存在的情况下，BPV1和EBV的分离/分配元件均可为小鼠多瘤病毒（PyV）核心起始质粒提供稳定维持功能，但对于完整的PyV起始位点则无法提供此功能。我们的研究首次追踪了BPV1 E2和微型染色体维持元件（MME）依赖的稳定维持功能与异源复制起始位点的关系。在表达PyV大T抗原（LT）以及BPV1 E2或EBV EBNA1的小鼠成纤维细胞系中，携带PyV最小起始位点以及MME或重复序列家族（FR）元件的质粒在非选择性条件下可轻松监测到长达1个月的长期附加体复制。我们的数据清楚地表明，PyV LT依赖的复制功能与BPV1或EBV的分离/分配功能在某些但并非所有配置中是兼容的。定量分析表明，在非选择性条件下，每个细胞的丢失率为6%，MME依赖的质粒翻倍，FR依赖的质粒为13%。我们的数据清楚地表明，不同病毒的维持功能原则上是可互换的，并且可以为多种细胞中的不同异源起始位点提供分离/分配功能。
