FIG. 6.

Plus-strand DNA synthesis by wild-type reverse transcriptase using model substrates. Extension assays were performed as described in the legend to Fig. 2, except that PPT62 was not 5′-end labeled and assays included [α-³²P]dGTP. Samples were collected at 0, 1, 4, or 16 min, treated with alkali, and analyzed in a 20% sequencing gel. Extension products were visualized using a PhosphorImager, and bands representing full-length extension products were quantified with ImageQuant Software using volume integration. Total extension products are plotted as a function of time. Filled diamonds, PPT62 alone in substrate I; filled squares, PPT62 followed by downstream RNA MLVnick in substrate II; filled triangles, PPT62 followed by downstream DNA MLVnickD in substrate II; open squares, hybrid substrate containing continuous 79-nt MLV RNA in substrate IV.