ESCHERICHIA-COLI MUTY-DEPENDENT MISMATCH REPAIR INVOLVES DNA-POLYMERASE-I AND A SHORT REPAIR TRACT

Repair of heteroduplex DNA containing an A/G mismatch in a mutL backgr ound requires the Escherichia coli mutY gene function. The mutY-depend ent in vitro repair of A/G mismatches is accompanied by repair DNA syn thesis on the DNA strand bearing mispaired adenines. The size of the m utY-dependent repair tract was measured by the specific incorporation of alpha[P-32]dCTP into different restriction fragments of the repaire d DNA. The repair tract is shorter than 12 nucleotides and longer than 5 nucleotides and is localized to the 3' side of the mismatched adeni ne. This repair synthesis is carried out by DNA polymerase I.