tailieunhanh - Báo cáo khoa học: Hepatitis C virus internal ribosome entry site-mediated translation is stimulated by cis-acting RNA elements and trans-acting viral factors

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 pro-cesses remains poorly characterized. | ỊFEBS Journal Hepatitis C virus internal ribosome entry site-mediated translation is stimulated by cis-acting RNA elements and trans-acting viral factors Sofia Lourenco1 Fleur Costa1 Beatrice Debarges1 Thibault Andrieu2 and Annie Cahour1 1 Laboratoire de Virologie . Paris France 2 Departement de Neurologie CEA Fontenay aux Roses France Keywords 3 -noncoding region in vivo reporter system IRES luciferase genes viral proteins Correspondence A. Cahour Laboratoire de Virologie . UPRES EA 2387 Groupe Hospitalier Pitié-Salpêtrière 83 Bd de l Hopital 75651 Paris Cedex 13 France Fax 33 145 82 6314 Tel 33 145 82 6298 E-mail cahour@ Received 29 February 2008 revised 9 May 2008 accepted 20 June 2008 doi 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 . 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 .