THE APURINIC-APYRIMIDINIC ENDONUCLEASE-IV FAMILY OF DNA-REPAIR ENZYMES

Apurinic-apyrimidinic (AP) sites are DNA lesions that lack template in formation and are produced either spontaneously or by a variety of DNA damaging agents. AP sites must therefore be repaired; otherwise they are mutagenic. All cells investigated to date possess the DNA repair e nzyme AP endonuclease that can repair AP sites. There are two discrete families of AP endonucleases, fro UI and Endo IV, which are exemplifi ed by Escherichia coli exonuclease III and endonuclease IV, respective ly. These AP endonucleases have evolved not only to repair AP sites bu t also to correct distinct DNA lesions.