Wang F, Petti L, Braun D, Seung S, Kieff E
J Virol. 1987 Apr;61(4):945-54. doi: 10.1128/JVI.61.4.945-954.1987.
EBNA2 is a nuclear protein expressed in all cells latently infected with and growth transformed by Epstein-Barr virus (EBV) infection (K. Hennessy and E. Kieff, Science 227:1230-1240, 1985). The nucleotide sequence of the EBNA2 mRNA (J. Sample, M. Hummel, D. Braun, M. Birkenbach, and E. Kieff, Proc. Natl. Acad. Sci. USA 83:5096-5100, 1986) revealed that it begins with a 924-base open reading frame that has an unusual potential translational initiation site (CAAATGG). This open reading frame is followed by 138 nucleotides with only one highly unlikely translational initiation site (TACATGC), which would translate a pentapeptide before the next stop codon. The last part of the mRNA is the open reading frame which encodes EBNA2. In this paper, we demonstrate that the 924-base open reading frame translates a 40-kilodalton protein in vitro or in murine cells transfected with the EBNA2 cDNA under control of the murine leukemia virus long terminal repeat. A protein of identical size was detected in EBV-transformed, latently infected human lymphocyte nuclei by using antibody specific for the leader open reading frame expressed in bacteria. Therefore, this is a rare example of a mRNA which translates two proteins from nonoverlapping open reading frames. Since the protein encoded by the leader of the EBNA mRNA is expressed in all nuclei of a latently infected cell line, it was designated EBNA-LP. EBNA-LP localizes to small intranuclear particles and differs in this respect from EBNA1, EBNA2, or EBNA3. EBNA-LP is not expressed in an EBV-transformed marmoset lymphocyte cell (B95-8) or in one EBV-infected Burkitt tumor cell line (Raji) but is expressed in three other Burkitt tumor cell lines (Namalwa, P3HR-1, and Daudi).
EBNA2是一种核蛋白，在所有被爱泼斯坦-巴尔病毒（EBV）潜伏感染并因该病毒感染而发生生长转化的细胞中表达（K. 轩尼诗和E. 基夫，《科学》227:1230 - 1240，1985年）。EBNA2 mRNA的核苷酸序列（J. 桑普尔、M. 胡梅尔、D. 布劳恩、M. 比尔肯巴赫和E. 基夫，《美国国家科学院院刊》83:5096 - 5100，1986年）显示，它起始于一个924个碱基的开放阅读框，该开放阅读框有一个不寻常的潜在翻译起始位点（CAAATGG）。这个开放阅读框之后是138个核苷酸，只有一个极不可能的翻译起始位点（TACATGC），该位点会在出现下一个终止密码子之前翻译出一个五肽。mRNA的最后一部分是编码EBNA2的开放阅读框。在本文中，我们证明，在鼠白血病病毒长末端重复序列的控制下，这个924个碱基的开放阅读框在体外或在转染了EBNA2 cDNA的鼠细胞中翻译出一种40千道尔顿的蛋白质。通过使用针对在细菌中表达的前导开放阅读框的特异性抗体，在EBV转化的、潜伏感染的人淋巴细胞核中检测到了大小相同的一种蛋白质。因此，这是一个mRNA从非重叠开放阅读框翻译出两种蛋白质的罕见例子。由于EBNA mRNA前导序列编码的蛋白质在潜伏感染细胞系的所有细胞核中都有表达，所以它被命名为EBNA-LP。EBNA-LP定位于核内小颗粒，在这方面与EBNA1、EBNA2或EBNA3不同。EBNA-LP在EBV转化的狨猴淋巴细胞细胞（B95 - 8）或一种EBV感染的伯基特肿瘤细胞系（拉吉细胞系）中不表达，但在其他三种伯基特肿瘤细胞系（纳马勒瓦细胞系、P3HR - 1细胞系和道迪细胞系）中表达。
