Fig. 1.

Polε-P301R retains weak 3ʹ→5ʹ exonuclease activity and is more accurate than the proofreading-deficient Polε. a Exonuclease activity of wild-type Polε (WT), exo⁻ Polε and Polε-P301R was assayed with 25 nM P50/T80 oligonucleotide substrate and 6.25 nM polymerase. Representative of >10 independent experiments. b Exonuclease activity of the Polε variants was assayed with 25 nM P50 single-stranded oligonucleotide and 4 nM polymerase. Representative of six independent experiments. c lacZ mutation frequencies resulting from in vitro DNA synthesis by wild-type Polε, exo⁻ Polε and Polε-P301R. d In vitro error rates for the 12 possible base-base mispairs generated by exo⁻ Polε and Polε-P301R. Source data for a and b are provided in a Source Data file. Data for c and d are from Supplementary Table 1. Asterisks indicate statistically significant differences between exo⁻ Polε and Polε-P301R: *p < 0.05; **p < 0.01 (Fisher’s exact test)