FIGURE 7.

WRN enables DNA Pol δ to preferentially extend a primer bearing a single 3′- terminal G:T mismatched nucleotide. Wild-type WRN and/or DNA Pol δ exo (−) were incubated with 10 nm primer-template DNA containing either a matched (A) or a single 3′-terminal mismatched nucleotide (B). DNA Pol δ exo (−) was used at 5 fmol per reaction, whereas WRN was used at 30 fmol (A) or at 6, 15, and 30 fmol (1, 2, and 3, respectively, in B). As controls, WRN (15 fmol) was also incubated with either Pol η (∼0.3 fmol; C) or Pol β (2 fmol; D). After 10 min at 37 °C in the presence of 100 μm concentrations of each of the four dNTPs, reactions were terminated, and aliquots were electrophoresed through urea-14% polyacrylamide gels. Gels were dried, and reaction products were visualized on a PhosphorImager.