Brooks L, Yao Q Y, Rickinson A B, Young L S
Department of Cancer Studies, University of Birmingham, United Kingdom.
J Virol. 1992 May;66(5):2689-97. doi: 10.1128/JVI.66.5.2689-2697.1992.
Epstein-Barr virus (EBV) genome-positive nasopharyngeal carcinomas (NPCs) regularly express the virus-coded nuclear antigen EBNA1, but not other EBNAs, and a subset of tumors also appear to be latent membrane protein LMP1 positive; the status of NPCs with respect to a second virus-coded latent membrane protein LMP2 is unknown. In the present work the EBV-NPC cell interaction has been analyzed at the RNA level with reverse transcription and polymerase chain reaction-based amplification to detect specific latent viral mRNAs. All four transplantable NPC cell lines studied and 17 of 18 fresh snap-frozen NPC biopsy specimens expressed an EBNA1 mRNA with a BamHI Q/U/K splice structure exactly like that recently identified in group I Burkitt's lymphoma (BL) cell lines and shown to be driven from a novel viral promoter, Fp. The BamHI Y3/U/K-spliced EBNA1 mRNA characteristic of virus-transformed B-lymphoblastoid cell lines (LCLs) was never found in NPCs. These same NPC biopsy specimens were then analyzed for evidence of the various LMP transcripts which are constitutively expressed in LCLs but down-regulated in BL cells. While only 3 of 18 tumors gave a clear LMP1 mRNA-specific signal after first-round amplification with either of two sets of polymerase chain reaction primers, the majority proved to be LMP1 mRNA positive after second-round amplification with nested primers. A rather similar pattern of results was obtained with respect to LMP2B mRNA expression, such transcripts being detectable only in a subset of tumors, and then at apparently low levels. In contrast, clear evidence of LMP2A mRNA expression was obtained in 17 of 17 fresh biopsies. The predominant form of EBV infection in NPCs, with coexpression of EBNA1 and LMP mRNAs, is therefore quite distinct from that seen in BL cells (in which EBNA1 is the only expressed mRNA) and in LCL cells (in which all six EBNA and three LMP transcripts are present). This third form of EBV latency may not be restricted to NPC but may have more general relevance in the context of EBV infection in vivo.
爱泼斯坦-巴尔病毒（EBV）基因组阳性的鼻咽癌（NPC）通常表达病毒编码的核抗原EBNA1，但不表达其他EBNAs，并且一部分肿瘤似乎也是潜伏膜蛋白LMP1阳性；关于第二种病毒编码的潜伏膜蛋白LMP2，NPC的状态尚不清楚。在本研究中，利用逆转录和基于聚合酶链反应的扩增技术在RNA水平上分析了EBV与NPC细胞的相互作用，以检测特定的潜伏病毒mRNA。所研究的所有四种可移植NPC细胞系以及18份新鲜速冻NPC活检标本中的17份表达了具有BamHI Q/U/K剪接结构的EBNA1 mRNA，其结构与最近在I型伯基特淋巴瘤（BL）细胞系中鉴定出的结构完全相同，并已证明是由一个新的病毒启动子Fp驱动的。在NPC中从未发现病毒转化的B淋巴母细胞系（LCL）所特有的BamHI Y3/U/K剪接的EBNA1 mRNA。然后对这些相同的NPC活检标本进行分析，以寻找各种LMP转录本的证据，这些转录本在LCL中组成性表达，但在BL细胞中下调。虽然在使用两组聚合酶链反应引物中的任何一组进行第一轮扩增后，18个肿瘤中只有3个产生了明确的LMP1 mRNA特异性信号，但在使用巢式引物进行第二轮扩增后，大多数肿瘤被证明是LMP1 mRNA阳性。关于LMP2B mRNA表达，也获得了相当相似的结果模式，此类转录本仅在一部分肿瘤中可检测到，且水平明显较低。相比之下，在17份新鲜活检标本中的17份中获得了LMP2A mRNA表达的明确证据。因此，NPC中EBV感染的主要形式，即EBNA1和LMP mRNA的共表达，与BL细胞（其中EBNA1是唯一表达的mRNA）和LCL细胞（其中存在所有六种EBNA和三种LMP转录本）中所见的形式截然不同。EBV潜伏的这种第三种形式可能不仅限于NPC，而是可能在体内EBV感染的背景下具有更广泛的相关性。
