FIGURE 1.

Incorporation of rCTP by human Pol ϵ. Purified Exo− human Pol ϵ (1 nm) was incubated with 18-mer/45-mer substrate (100 nm) for 10 min at 37 °C in the presence of a 250 μm concentration of each of dATP, dGTP, and dTTP. The rCTP nucleotide was either withheld (−rCTP) or added at 250 μm (+rCTP). These reaction products were incubated with either 300 mm KCl or 300 mm KOH for 2 h at 55 °C. Products were resolved on a 12% denaturing gel. Black arrowheads indicate extension products containing incorporated rNMPs that were hydrolyzed by alkaline treatment. The template sequence is shown to the right.