Fig. 1. Circular duplex substrates used for mismatch repair and gap-filling assays. All the circular duplex substrates used in this study were prepared by annealing linearized double-stranded plasmid DNA and single-stranded circular viral DNA. (A) The A/C substrate is shown as a representative of the standard mismatch repair substrates. (B) ‘Far nicked’ A/C mismatched substrate. The nick was moved from the standard position, 580 bp 3′ to the mismatch, to a position 1500 bp on the 5′ side. (C) The GAP1 substrate contains a 599 base gap. (D) The GAP2 substrate contains a 1147 base gap. GAP1 and GAP2 were used as standards for the gap-filling assay and for estimation of repair patch size as described in Materials and methods.