Figure 5.

Effect of DNA ligase I on PCNA-dependent DNA synthesis by DNA polymerase δ. PCNA (132 ng, 4.6 pmol) was preincubated with DNA ligase I as indicated for 30 min at 37°C in a final volume of 20 μl. BSA was added to the reactions so that the final protein concentration was the same in each assay. Preincubated proteins were added to reaction mixtures containing oligo(dT)/poly(dA), [³H]TTP, and 0.2 units DNA pol δ in a final volume of 60 μl, and incubation was continued for 30 min at 37°C. Incorporation of [³H]TMP was measured as described in Materials and Methods.