Miller G, Rabson M, Heston L
J Virol. 1984 Apr;50(1):174-82. doi: 10.1128/JVI.50.1.174-182.1984.
By cloning the HR-1 Burkitt lymphoma line, we previously uncovered two distinct biological variants of nontransforming Epstein-Barr virus (EBV). The most commonly cloned variant has a low rate of spontaneous viral synthesis and is unable to induce early antigen in Raji cells (EAI-). A rare variant spontaneously releases virus which is capable of inducing early antigen in Raji cells (EAI+). Since EAI- virus lacks heterogeneous DNA (het-) and EAI+ virus contains heterogeneous DNA (het+), we suggested that spontaneous viral synthesis and induction of early antigen are biological properties which correlate with the presence of het sequences. The present experiments provide three new lines of experimental evidence in favor of this hypothesis. (i) Revertant subclones of the EAI+ het+ variant which have lost the het DNA concomitantly lost EAI ability. Thus, het DNA is not stably associated with the cells as are the episomes. (ii) het DNA was acquired by two het- subclones of the HR-1 line after superinfection with EAI+ virus. After superinfection, these clones synthesized EAI+ het+ virus. Thus, het DNA may be maintained in the HR-1 line by cell-to-cell spread. (iii) Virus with het DNA activated full expression of endogenous latent EBV of the transforming phenotype in a line of immortalized neonatal lymphocytes designated X50-7. By use of restriction endonuclease polymorphisms unique to both the superinfecting and endogenous genomes, we show that the genome of the activated virus resembles that of the virus which was endogenous to X50-7 cells. This result suggests that het sequences result in transactivation of the latent EBV. het DNA had homology with EBV sequences which are not normally contiguous on the physical map of the genome. het DNA was always accompanied by the presence of DNA of nonheterogenous HR-1. Thus, het DNA is a form of "defective" EBV DNA. However, the biological effect of this defective DNA is to enhance rather than to interfere with EBV replication. This is a novel property of defective virus.
通过克隆HR - 1伯基特淋巴瘤细胞系，我们先前发现了非转化型爱泼斯坦 - 巴尔病毒（EBV）的两种不同生物学变体。最常克隆的变体自发病毒合成率低，且无法在拉吉细胞中诱导早期抗原（EAI -）。一种罕见变体可自发释放能够在拉吉细胞中诱导早期抗原的病毒（EAI +）。由于EAI -病毒缺乏异质性DNA（het -），而EAI +病毒含有异质性DNA（het +），我们认为自发病毒合成和早期抗原诱导是与het序列存在相关的生物学特性。目前的实验提供了三条新的实验证据支持这一假说。（i）EAI + het +变体的回复性子克隆失去了het DNA，同时也失去了EAI能力。因此，het DNA不像附加体那样与细胞稳定相关。（ii）HR - 1细胞系的两个het -亚克隆在被EAI +病毒超感染后获得了het DNA。超感染后，这些克隆合成了EAI + het +病毒。因此，het DNA可能通过细胞间传播在HR - 1细胞系中得以维持。（iii）带有het DNA的病毒在一个名为X50 - 7的永生化新生儿淋巴细胞系中激活了具有转化表型的内源性潜伏EBV的完全表达。通过使用超感染病毒和内源性基因组特有的限制性内切酶多态性，我们表明激活病毒的基因组类似于X50 - 7细胞内源性病毒的基因组。这一结果表明het序列导致潜伏EBV的反式激活。het DNA与基因组物理图谱上通常不相邻的EBV序列具有同源性。het DNA总是伴随着非异质性HR - 1的DNA存在。因此，het DNA是“缺陷”EBV DNA的一种形式。然而，这种缺陷DNA的生物学效应是增强而非干扰EBV复制。这是缺陷病毒的一种新特性。
