Hepatitis C virus internal ribosome entry site-mediated translation is stimulated by cis-acting RNA elements and trans-acting viral factors
Hepatitis C virus internal ribosome entry site-mediated translation is stimulated by cis-acting RNA elements and trans-acting viral factors
复制标题
DOI：
10.1111/j.1742-4658.2008.06566.x
复制
发表时间：
2008-08-01
期刊：
影响因子：
5.4
通讯作者：
Cahour, Annie
中科院分区：
文献类型：
--
作者：
Lourenco, Sofia;Costa, Fleur;Cahour, Annie
丙型肝炎病毒（HCV）的翻译起始通过位于其5'端的内部核糖体进入位点（IRES）发生。作为一种正链RNA病毒，HCV使用其基因组作为翻译和复制的通用模板，但这两个过程之间的协调作用仍未得到很好的阐释。此外，尽管由于亚基因组复制子以及近期建立的HCV培养系统，有关病毒复制的RNA - 蛋白质相互作用的遗传学证据不断积累，但此类相互作用在翻译调控中仍存在争议。为了深入了解这些机制，我们利用基于细胞的RNA报告系统研究了顺式和反式病毒因子在HCV IRES活性中的作用。我们发现HCV 3'非编码区（NCR）在顺式作用下强烈刺激IRES效率，且这种作用取决于基因型和细胞系。此外，我们证实了核心蛋白在病毒基因表达中的作用，这与先前体外研究报道一致。令人惊讶的是，我们观察到了一种类似的效应，即在低量的NS5B RNA聚合酶存在下，效率提高两倍，而在较高浓度时则降低。然而，未发现NS5A对HCV IRES介导的翻译有贡献，也未检测到3' NCR与病毒蛋白之间或蛋白之间存在协同作用。总体而言，这些结果表明HCV RNA翻译受到调控，并且从翻译到复制的转换可能涉及对顺式和反式病毒因子的顺序需求，因为它们明显缺乏协同作用，可能还需要宿主因子的协助。
Translation initiation of hepatitis C virus (HCV) occurs through an internal ribosome entry site (IRES) located at its 5'-end. As a positive-stranded RNA virus, HCV uses its genome as a common template for translation and replication, but the coordination between these two processes remains poorly characterized. Moreover, although genetic evidence of RNA-protein interactions for viral replication is accumulating because of subgenomic replicons and a recent culture system for HCV, such interactions are still contentious in the regulation of translation. To gain insight into such mechanisms, we addressed the involvement of cis and trans viral factors in HCV IRES activity by using a cell-based RNA reporter system. We found that the HCV 3' noncoding region (NCR) strongly stimulates IRES efficiency in cis, depending on the genotype and the cell line. Moreover, we confirmed the role of the core protein in viral gene expression as previously reported in vitro. Surprisingly, we observed a similar effect, i.e. a twofold increase under low amounts of NS5B RNA polymerase, followed by a decrease at higher concentrations. However, no contribution of NS5A to HCV IRES-mediated translation was noted and no cooperative effect could be detected between 3' NCR and viral proteins or between proteins. Collectively, these results suggest that HCV RNA translation is regulated, and that the switch from translation to replication might involve a sequential requirement for both cis and trans viral factors, because of their apparent lack of synergy, probably with the aid of host factors.