Hepatitis C virus (HCV) translation begins within the internal ribosome entry site (IRES). We have previously isolated two RNA aptamers, 2-02 and 3-07. which specifically bind to domain II and domain III-IV of the HCV IRES, respectively, and inhibit IRES-dependent translation. To improve the function of these aptamers, we constructed two conjugated molecules of 2-02 and 3-07. These bound to the target RNA more efficiently than the two parental aptamers. Furthermore, they inhibited IRES-dependent translation about 10 times as efficiently as the 3-07 aptamer. This result indicates that combining aptamers for different target recognition sites potentiates the inhibition activity by enhancing the domain-binding efficiency. (C) 2009 Elsevier Inc. All rights reserved.