Floettmann J E, Ward K, Rickinson A B, Rowe M
Department of Medicine, University of Wales College of Medicine, Heath Park, Cardiff, United Kingdom.
Virology. 1996 Sep 1;223(1):29-40. doi: 10.1006/viro.1996.0452.
Tetracycline-regulated vectors were used to obtain inducible expression in stable transfected B cell lines of two Epstein-Barr virus (EBV) latent genes, LMP1 and EBNA2. The transfected genes were tightly repressed by low, nontoxic concentrations of tetracycline (< or = 1 microgram/ml) and, following removal of tetracycline, were induced to levels comparable to or up to 3x that of EBV-transformed normal lymphoblastoid cell lines. In transfected DG75 cells, induced expression of LMP1, but not of EBNA2, led to the expected upregulation of various cell surface markers, including: CD40, CD54, CD58, and HLA class I.A novel observation was that both LMP1 and EBNA2 independently caused the downregulation of surface IgM, an effect mirrored in EBV-positive Burkitt lymphoma lines undergoing phenotypic drift during the transition from latency I to latency III in which both LMP1 and EBNA2 are upregulated. Most remarkably, induced LMP1 expression almost completely inhibited cell growth for 4 to 5 days, after which the cells recovered a limited proliferative capacity. The cytostatic effect of LMP1 was observed in all three B cell lines studied: DG75, BJAB, and Akata. Further analysis showed that induction of LMP1 coincided with a reduction in the levels of c-myc, and that the cytostatic effect was due to an accumulation of cells at the G2/M phase of the cell cycle. These data suggest a novel function for the LMP1 oncogene in controlling the proliferation of EBV-infected cells by regulating progress through G2/M phase.
四环素调控载体被用于在稳定转染的B细胞系中诱导表达两种爱泼斯坦-巴尔病毒（EBV）潜伏基因，即潜伏膜蛋白1（LMP1）和EBNA2。转染的基因在低浓度、无毒的四环素（≤1微克/毫升）作用下被紧密抑制，去除四环素后，其表达水平可诱导至与EBV转化的正常淋巴母细胞系相当或高达其三倍。在转染的DG75细胞中，LMP1的诱导表达而非EBNA2的诱导表达导致了多种细胞表面标志物的预期上调，包括：CD40、CD54、CD58和I类人白细胞抗原。一个新的发现是，LMP1和EBNA2均可独立导致表面IgM的下调，这种效应在EBV阳性的伯基特淋巴瘤细胞系从潜伏期I向潜伏期III转变过程中发生表型漂移时也有体现，在此过程中LMP1和EBNA2均上调。最显著的是，诱导的LMP1表达在4至5天内几乎完全抑制细胞生长，之后细胞恢复了有限的增殖能力。在研究的所有三种B细胞系（DG75、BJAB和Akata）中均观察到了LMP1的细胞生长抑制作用。进一步分析表明，LMP1的诱导与c-myc水平的降低同时发生，且细胞生长抑制作用是由于细胞在细胞周期的G2/M期积累所致。这些数据表明LMP1癌基因通过调节G2/M期进程来控制EBV感染细胞增殖具有一种新功能。
