Figure 4.

Influence of APE1 on the strand-displacement DNA synthesis by pol β on matched and mismatched DNAs. The reaction conditions are described under Materials and Methods. The reaction mixtures containing ³²P-labeled DNA_F or DNA_P (50 nM) with matched or mismatched 3′-base pair, all four dNTPs (10 μM each) or a mixture of dATP, dGTP, dTTP (10 μM) each), dCTP (1 μM) and ddCTP (9 μM), were incubated at 37°C for 30 min with (+) or without (−) APE1 and pol β, as indicated. Schematic representations of the DNA substrates are shown at the top of the gel. The positions of the initial primer and the products of DNA synthesis and the APE1 exonuclease reaction are indicated.