FIG 4.

HIV-1 RT incorporates 5-aza-CTP much less efficiently than 5-aza-dCTP in vitro. The relative abilities of HIV-1 RT to incorporate 5-aza-CTP, 5-aza-dCTP, CTP, and dCTP were determined using an in vitro single nucleotide extension assay. The HIV-1 RT was incubated with a radiolabeled primer (18 nt) annealed to a DNA template (19 nt) in the presence of each compound at 5 nM to 500 μM (a 10-fold series, from left to right). Additional control reactions were performed by incubating with all four standard dNTPs (50 μM) (+) or by omitting RT (−). All of the reactions were analyzed on the same gel.