FIGURE 6.

RNA 5′-end-directed RNase H activity of HIV-1 RT proteins. A, the substrates used were made by annealing a 77-nt DNA primer to a 5′-end-labeled 41-nt RNA template. Two sequential RNase H cleavages occur that are indicated as the primary and secondary cuts. B, the reactions were performed using equivalent amounts of polymerase activity of the wild-type, M184I, and M184A in the absence of dNTPs. Reactions were sampled at different time points, as indicated above the gel. Lane C is a control reaction in the absence of RT. C, quantitation of the amount of uncleaved substrate over time. The percentage of uncleaved substrate for each time point was calculated as ((uncleaved substrate/(primary cuts + secondary cuts + uncleaved substrate)) × 100%). Results represent the average of three independent experiments.