Cotton Sophie, Dufresne Philippe J, Thivierge Karine, Ide Christine, Fortin Marc G
Department of Plant Science, McGill University, 21,111 Lakeshore, Ste-Anne-de-Bellevue, Québec, Canada H9X 3V9.
Virology. 2006 Jul 20;351(1):92-100. doi: 10.1016/j.virol.2006.03.019. Epub 2006 May 2.
A role for viral encoded genome-linked (VPg) proteins in translation has often been suggested because of their covalent attachment to the 5' end of the viral RNA, reminiscent of the cap structure normally present on most eukaryotic mRNAs. We tested the effect of Turnip mosaic virus (TuMV) VPgPro on translation of reporter RNAs in in vitro translation systems. The presence of VPgPro in either wheat germ extract or rabbit reticulocyte lysate systems lead to inhibition of translation. The inhibition did not appear to be mediated by the interaction of VPg with the eIF(iso)4E translation initiation factor since a VPg mutant that does not interact with eIF(iso)4E still inhibited translation. Monitoring the fate of RNAs revealed that they were degraded as a result of addition of TuMV VPgPro or of Norwalk virus (NV) VPg protein. The RNA degradation was not the result of translation being arrested and was heat labile and partially EDTA sensitive. The capacity of TuMV VPgPro and of (NV) VPg to degrade RNA suggests that these proteins have a ribonucleolytic activity which may contribute to the host RNA translation shutoff associated with many virus infections.
由于病毒编码的基因组连接蛋白（VPg）与病毒RNA的5'端共价连接，这让人联想到大多数真核生物mRNA上通常存在的帽结构，因此人们常常认为VPg蛋白在翻译过程中发挥作用。我们在体外翻译系统中测试了芜菁花叶病毒（TuMV）VPgPro对报告RNA翻译的影响。在小麦胚芽提取物或兔网织红细胞裂解物系统中存在VPgPro均会导致翻译抑制。这种抑制似乎不是由VPg与eIF(iso)4E翻译起始因子的相互作用介导的，因为一个不与eIF(iso)4E相互作用的VPg突变体仍然抑制翻译。监测RNA的命运发现，由于添加了TuMV VPgPro或诺沃克病毒（NV）VPg蛋白，它们会被降解。RNA降解不是翻译停滞的结果，并且对热不稳定且部分对EDTA敏感。TuMV VPgPro和NV VPg降解RNA的能力表明，这些蛋白具有核糖核酸酶活性，这可能有助于许多病毒感染相关的宿主RNA翻译关闭。
