Allday M J, Crawford D H, Griffin B E
Department of Virology, Royal Postgraduate Medical School, London, U.K.
J Gen Virol. 1989 Jul;70 ( Pt 7):1755-64. doi: 10.1099/0022-1317-70-7-1755.
Epstein-Barr virus (EBV) has the capacity to immortalize a subpopulation of resting B lymphocytes. Lymphoblastoid cell lines (LCL) established in this way carry the latent EBV genome as multiple copies of an extrachromosomal episome. Viral gene expression in LCLs is highly restricted; products identified correspond to a membrane protein (latent membrane protein; LMP), a nuclear antigen complex (Epstein-Barr nuclear antigens; EBNAs 1 to 6), two small RNA species (EBERs 1 and 2) and RNA species thought to encode a second membrane-associated polypeptide designated terminal protein (TP). Here we have investigated the temporal sequence of expression of the characterized 'latent' proteins during the initiation of immortalization when resting B cells are stimulated to enter and traverse the cell cycle. The analysis has been carried out on prolymphocytic leukaemia cells infected in vitro with either the immortalizing B95-8 strain of virus or the non-immortalizing P3HR1 strain. The results reveal that following B95-8 infection, a sequence of EBV expression is initiated within approximately 8 h with the synthesis of detectable levels of EBNA 2 shortly followed by EBNAs 1, 3, 4, 5 and 6. There is then a delay of approximately 40 h until the expression of LMP completes the latent pattern of proteins found in LCLs. P3HR1 infection, however, produces only transient expression of some EBNA species in a small percentage of cells after approximately 48 h. These observations suggest the failure of P3HR1 virus to immortalize may not be due solely to the absence of EBNA 2 expression and that cellular and/or virus-mediated events occur after EBNA synthesis which then facilitate efficient LMP expression and immortalization.
爱泼斯坦-巴尔病毒（EBV）能够使一部分静止B淋巴细胞永生化。以这种方式建立的淋巴母细胞系（LCL）携带潜伏性EBV基因组，作为染色体外附加体的多个拷贝。LCL中的病毒基因表达受到高度限制；鉴定出的产物对应于一种膜蛋白（潜伏膜蛋白；LMP）、一种核抗原复合物（爱泼斯坦-巴尔核抗原；EBNAs 1至6）、两种小RNA（EBERs 1和2）以及被认为编码另一种称为末端蛋白（TP）的膜相关多肽的RNA。在这里，我们研究了在静止B细胞被刺激进入并经历细胞周期的永生化起始过程中，已鉴定的“潜伏”蛋白的表达时间顺序。分析是在体外感染了永生化病毒B95-8株或非永生化P3HR1株的原淋巴细胞白血病细胞上进行的。结果显示，在感染B95-8后，大约8小时内开始了EBV表达序列，可检测水平的EBNA 2合成后不久，接着是EBNAs 1、3、4、5和6。然后有大约40小时的延迟，直到LMP的表达完成了LCL中发现的潜伏蛋白模式。然而，P3HR1感染在大约48小时后仅在一小部分细胞中产生一些EBNA种类的短暂表达。这些观察结果表明，P3HR1病毒无法永生化可能不仅仅是由于缺乏EBNA 2表达，并且在EBNA合成后发生了细胞和/或病毒介导的事件，这些事件随后促进了有效的LMP表达和永生化。
