Mismatch repair involving localized DNA synthesis in extracts of Xenopus eggs.

Repair of heteroduplex DNA containing G.T or A.C mismatches or containing two tandem unpaired bases occurred in vitro with Xenopus egg extracts as detected by a physical assay. The repair was accompanied by a mismatch-stimulated and mismatch-localized DNA synthesis. Repaired molecules, separated from unrepaired molecules, showed a 20- to 100-fold increase in DNA synthesis in the region of the mismatch compared to regions distant from the mismatch. The remaining unrepaired heteroduplex DNA included molecules that also displayed mismatch-stimulated DNA synthesis in the mismatch-proximal regions. These may represent intermediates in the repair process. The patterns of DNA synthesis suggest that repair begins at some distance from the mismatch and that as much as 1 kilobase or more can be involved in the mismatch-stimulated synthesis.