FIG. 6.

RNA synthesis by the HCV RdRp in the presence of ribavirin triphosphate. (A) Autoradiogram of the products made by Δ21 under different reaction conditions. RTP was added to reactions lacking either GTP or both GTP and ATP, as indicated by the notations −G and −G,−A. The 32-nt product in lanes 17 to 20 demonstrates that RTP was incorporated during elongative synthesis in place of ATP. (B) An assay to confirm that RTP cannot serve as the initiation NTP. The assay used the puromycin-modified LE19P. The control reactions are indicated by +G. (C) Examination of whether RTP inhibits RNA synthesis by the HCV RdRp in reactions containing all of the normal NTPs. The level of synthesis was quantified and normalized to one lacking RTP.