The Roles of Dicer and TRBP in HCV Replication

MicroRNAs (miRNAs) are non-coding small RNAs that regulate eukaryotic gene activity at the post-transcriptional level by a process termed miRNA gene suppression. MicroRNA-122 (miR-122) is predominantly expressed in human liver cells and recent studies indicated that miR-122 promotes Hepatitis C Virus (HCV) replication and translation through physical interaction with two tandem binding sites located in the 5’ untranslated region (5’UTR) of the HCV genome (Jopling, et al., 2006; Jopling, et al., 2008). It has been reported that host genes that are also implicated in the miRNA gene suppression pathway are key regulators of HCV replication (Randall, et al., 2007). Two proteins, Dicer, a key RNaseIII enzyme, and its binding partner TRBP are essential proteins for miRNA activity. They are part of a protein complex called the RNA induced silencing complex (RISC) which also includes Argonaute proteins, and function in miRNA biogenesis loading the miRNA into RISC. As such, they are intriguing targets to study host-viral interplay during HCV replication. In our study, we designed siRNAs to knock down Dicer and TRBP and then observed the effects of gene knockdown on full length J6/JFH-1-RLuc HCV (genotype 2a chimeric genome) replication and translation. The results showed that knocking down Dicer and TRBP reduced wild type (wt) J6/JFH-1-RLuc replication but had almost no effects on HCV translation in human liver cells. However, since knocking down Dicer and TRBP did not significantly alter miR-122 levels in the cell, it appears that the role of Dicer and TRBP was not solely the biogenesis of miR-122. This was confirmed by an experiment in which we observed that knocking down Dicer and TRBP also attenuated replication of