Chen Min-Hsin, Icenogle Joseph P
Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
J Virol. 2004 Apr;78(8):4314-22. doi: 10.1128/jvi.78.8.4314-4322.2004.
The structural proteins (SP) of the Togaviridae can be deleted in defective interfering RNAs. The dispensability of viral SP has allowed construction of noninfectious viral expression vectors and replicons from viruses of the Alphavirus and Rubivirus genera. Nevertheless, in this study, we found that the SP of rubella virus (RUB) could enhance expression of reporter genes from RUB replicons in trans. SP enhancement required capsid protein (CP) expression and was not due to RNA-RNA recombination. Accumulation of minus- and plus-strand RNAs from replicons was observed in the presence of SP, suggesting that SP specifically affects RNA synthesis. By using replicons containing an antibiotic resistance gene, we found 2- to 50-fold increases in the number of cells surviving selection in the presence of SP. The increases depended significantly on the amount of transfected RNA. Small amounts of RNA or templates that replicated inefficiently showed more enhancement. The infectivity of infectious RNA was increased by at least 10-fold in cells expressing CP. Moreover, virus infectivity was greatly enhanced in such cells. In other cells that expressed higher levels of CP, RNA replication of replicons was inhibited. Thus, depending on conditions, CP can markedly enhance or inhibit RUB RNA replication.
披膜病毒科的结构蛋白（SP）可在缺陷干扰RNA中缺失。病毒SP的可缺失性使得能够从甲病毒属和风疹病毒属的病毒构建非感染性病毒表达载体和复制子。然而，在本研究中，我们发现风疹病毒（RUB）的SP可反式增强RUB复制子中报告基因的表达。SP增强需要衣壳蛋白（CP）表达，且并非由于RNA - RNA重组。在存在SP的情况下，观察到来自复制子的负链和正链RNA的积累，这表明SP特异性影响RNA合成。通过使用含有抗生素抗性基因的复制子，我们发现在存在SP的情况下，存活于选择过程中的细胞数量增加了2至50倍。这种增加显著依赖于转染RNA的量。少量RNA或复制效率低的模板显示出更多的增强作用。在表达CP的细胞中，感染性RNA的感染力至少增加了10倍。此外，在这类细胞中病毒感染力大大增强。在其他表达较高水平CP的细胞中，复制子的RNA复制受到抑制。因此，根据条件不同，CP可显著增强或抑制RUB RNA复制。
