Effects of HCV 3′UTR containing different lengths of PolyU/UC tract isolated from chronic HCV infected patients on IRES-mediated translation and RNA synthesis by NS5B polymerase
Objective To investigate the effects of HCV 3′UTR containing different lengths of PolyU/UC tract on IRES-mediated translation and RNA synthesis by NS5B polymerase. Methods A variety of 3′UTRs containing different lengths of PolyU/UC tract were obtained from HCV chronic infected patients and cloned respectively to the downstream of the HCV internal ribosome entry site(IRES) linked to the firefly luciferase coding gene. In vitro translation and cell transfection assays were employed to detect the activities of reporter firefly luciferase. Results In both in vitro and cell transfection assays, the IRES-mediated translation could be only enhanced by 3′UTR. However, such effect was correlated with the length of PolyU/UC tract in in vitro system, but not in cell transfection assay. 3′UTR showed an inhibitory effect on the activity of NS5B polymerase in cell transfection assay, and the inhibitory effect was not correlated with the length of PolyU/UC tract. Conclusion HCV 3′UTR plays an important role in viral protein translation and RNA synthesis, but such effect was not regulated by the length of PolyU/UC tract in cells.