Fig. 2.

Exo1-independent mismatch repair in a purified human system. (A) Reactions containing 3′ G–T heteroduplex DNA, MutSα, MutLα, RFC, PCNA, RPA, DNA polymerase δ, and ATP (MMR set; see Materials and Methods) were supplemented with Exo1 or Fen1 as indicated. Gels show repair (Left) or excision (Right) in the presence or absence of the 4 dNTPs respectively, using the methods outlined in Fig. 1. Excision on otherwise identical A·T homoduplex DNA was ≤5% under all conditions. (B) Kinetics of mismatch repair in the presence of MutSα, MutLα, RFC, PCNA, RPA, DNA polymerase δ, and ATP (MMR set) plus the 4 dNTPs, in the presence of the MMR set-dNTP mix from which MutSα was omitted or in the presence of the MMR set, dNTPs and Exo1.