FIGURE 8.

Extension of a mismatched primer terminus by DNA Pol δ requires removal of the mismatch by WRN. Two equivalent amounts (30 and 60 fmol) of either wild-type (W1 and W2) or exonuclease-minus WRN (E1 and E2) were incubated with DNA Pol δ exo (−) (5 fmol) and G:T mismatched P/T DNA (A). Alternatively, fixed concentrations of WRN (15 fmol) and Pol δ (3 fmol) were incubated with P/T DNA in which the terminal two nucleotides were linked with a thio bond (Thio-mismatch, B) or in reaction mixtures lacking dATP (−) dATP, C). Reactions were carried out and processed as described.