Dr. Sarnow's laboratory has been been studying the mechanism by which a liver-specific microRNA, miR-122, regulates the amplification of the hepatitis C virus (HCV) genome in cultured cells. Specifically, we have found that miR-122 interacts with the 5' end of the viral RNA and is essential for viral replication. Consequently, sequestration of miR-122 by antisense-oligonucleotides results in rapid loss of viral RNA. They are currently examining the mechanism by which miR-122 helps HCV RNA replication and are searching for cellular targets of miR-122 and their regulation by miR-122. These lines of investigations will lead to new insights how these small noncoding RNAs regulate expression of cellular and viral mRNAs and may point to new venues for antiviral therapeutics against HCV.