Refractoriness of hepatitis C virus internal ribosome entry site to processing by Dicer in vivo
1 Centre de Recherche en Rhumatologie et Immunologie, CHUL Research Center/CHUQ, 2705 Blvd Laurier, Quebec, QC, G1V 4G2, Canada
2 Faculty of Medicine, Université Laval, Quebec, QC, G1V 0A6, Canada
Journal of Negative Results in BioMedicine 2009, 8:8 doi:10.1186/1477-5751-8-8Published: 13 August 2009
Hepatitis C virus (HCV) is a positive-strand RNA virus harboring a highly structured internal ribosome entry site (IRES) in the 5' nontranslated region of its genome. Important for initiating translation of viral RNAs into proteins, the HCV IRES is composed of RNA structures reminiscent of microRNA precursors that may be targeted by the host RNA silencing machinery.
We report that HCV IRES can be recognized and processed into small RNAs by the human ribonuclease Dicer in vitro. Furthermore, we identify domains II, III and VI of HCV IRES as potential substrates for Dicer in vitro. However, maintenance of the functional integrity of the HCV IRES in response to Dicer overexpression suggests that the structure of the HCV IRES abrogates its processing by Dicer in vivo.
Our results suggest that the HCV IRES may have evolved to adopt a structure or a cellular context that is refractory to Dicer processing, which may contribute to viral escape of the host RNA silencing machinery.