Figure 1
From: Regulation of gene expression by microRNA in HCV infection and HCV–mediated hepatocellular carcinoma
Biogenesis of miRNA. miRNAs are transcribed from the genes by RNA polymerase II. The microprocessor complex (Drosha and DGCR8) processes the primary miRNA transcripts into pre-miRNA. The pre-miRNA is then exported into the cytoplasm by exportin-5 and processed into a RNA duplex by ribonuclease Dicer in association with TRBP. The end product is 22 bp double stranded RNA. One strand of the dsRNA remains bound to the dicer to form the mature miRNA while the other RNA strand is generally degraded. The remaining strand is then assembled into the RISC with Ago 2 and can target gene silencing through either cleavage or translational repression.