A repair enzyme, MutS, binds to mismatches in DNA and recruits MutL, which subsequently activates the endonuclease MutH. MutH binds hemimethylated GATC sites and when activated will selectively cleave the unmethylated daughter strand, allowing helicase and exonucleases to excise the nascent strand in the region surrounding the mismatch.
A repair enzyme called MutS recognizes mismatched DNA sequences and recruits another enzyme, MutL. This activates an endonuclease called MutH, which specifically cuts the unmethylated daughter strand near a GATC site.  This allows for the removal of the damaged section by helicase and exonucleases.