Human apurinic/apyrimidinic (AP) endonuclease, APE 1, also known as HAP 1 or Ref-1, shares homology with E

APE 1 cleaves the phosphodiester backbone immediately 5´ to an AP site via hydrolytic mechanism, generating a ssDNA break that leaves a 3´-hydroxyl and 5´-deoxyribose phosphate terminus. Besides AP endonuclease activity, APE 1 has also been reported to have weak DNA 3´-diesterase, 3´ to 5´ exonuclease and RNase H activities. In addition to DNA repair, APE 1 can also regulate the DNA binding activity of many transcription factors in vitro. APE 1 can also stimulate the DNA binding activity of Fos-Jun heterodimers, Jun-Jun homodimers and HeLa cell AP-1 proteins as well as that of several other transcription factors including NF-kB, Myb and members of the ATF/CREB family.

coli Exonuclease III.