Ligation of polβ 8-oxodGTP insertion products by ligase IIIα in the presence of XRCC1.A, illustration of the one nucleotide gap DNA substrate and the insertion, mutagenic ligation, and ligation failure products observed in the coupled assays including polβ, ligase IIIα, and/or XRCC1. B, line 1 is the negative enzyme control of the one nucleotide gap DNA substrate with template A. Lanes 2 to 5 are the ligation of polβ 8-oxodGTP:A insertion products by ligase IIIα in the absence of XRCC1. Lanes 6 to 9 and 10 to 13 are polβ 8-oxodGTP:A insertion coupled to ligation products in the presence of XRCC1 wild-type and V86R mutant, respectively, and correspond to time points of 0.5, 1, 2, and 3 min. C and D, the graphs show time-dependent changes in the amount of mutagenic ligation (C) and ligation failure (D) products. The data represent the average of three independent experiments ±SD. The bar graphs with individual data points are presented in Fig. S12.