Certo J L, Shook B F, Yin P D, Snider J T, Hu W S
Department of Genetics and Developmental Biology, West Virginia University, Morgantown, West Virginia 26506, USA.
J Virol. 1998 Jul;72(7):5408-13. doi: 10.1128/JVI.72.7.5408-5413.1998.
It has been documented that spleen necrosis virus (SNV) can package murine leukemia virus (MLV) RNA efficiently and propagate MLV vectors to the same titers as it propagates SNV-based vectors. Although the SNV packaging signal (E) and MLV packaging signal (Psi) have little sequence homology, similar double-hairpin RNA structures were predicted and supported by experimental evidence. To test whether SNV RNA can be packaged by MLV proteins, we modified an SNV vector to be expressed in an MLV-based murine helper cell line. Surprisingly, we found that MLV proteins could not support the replication of SNV vectors. The decrease in titer was approximately 2,000- to 20,000-fold in one round of retroviral replication. RNA analysis revealed that SNV RNA was not efficiently packaged by MLV proteins. RNA hybridization of the cellular and viral RNAs indicated that SNV RNA was packaged at least 25-fold less efficiently than MLV RNA, which was the sensitivity limit of the hybridization assay. The contrast between the MLV and SNV packaging specificity is striking. SNV proteins can recognize both SNV E and MLV Psi, but MLV can recognize only MLV Psi. This is the first demonstration of two retroviruses with nonreciprocal packaging specificities.
已有文献记载，脾坏死病毒（SNV）能够高效包装鼠白血病病毒（MLV）RNA，并将MLV载体扩增至与基于SNV的载体相同的滴度。尽管SNV包装信号（E）和MLV包装信号（Ψ）的序列同源性很低，但预测其具有相似的双发夹RNA结构，且有实验证据支持。为了测试SNV RNA是否能被MLV蛋白包装，我们对一个SNV载体进行了改造，使其能在基于MLV的鼠辅助细胞系中表达。令人惊讶的是，我们发现MLV蛋白无法支持SNV载体的复制。在一轮逆转录病毒复制中，滴度下降了约2000至20000倍。RNA分析表明，SNV RNA不能被MLV蛋白有效包装。细胞RNA和病毒RNA的杂交结果显示，SNV RNA的包装效率至少比MLV RNA低25倍，这是杂交检测的灵敏度极限。MLV和SNV包装特异性之间的差异十分显著。SNV蛋白既能识别SNV的E信号，也能识别MLV的Ψ信号，但MLV只能识别MLV的Ψ信号。这是首次证明两种逆转录病毒具有非相互性的包装特异性。
