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To understand the mechanism involved in the coordination of the sequential repair reactions that lead to long-patch BER, we have investigated interactions between proteins involved in this pathway. We find that human AP endonuclease 1 (APE1) physically interacts with flap endonuclease 1 (FEN1) and with proliferating cell nuclear antigen. An oligonucleotide substrate containing a reduced abasic site, which was pre-incised with APE1, was employed to reconstitute the excision step of long-patch BER with purified human DNA polymerase beta and FEN1. We demonstrate that addition of APE1 to the excision reaction mixture slightly (1.5-2-fold) stimulates the removal of the displaced flap by FEN1. These results suggest the possibility that long-patch BER is coordinated and directed by protein-protein interactions.


Journal article



Publication Date





12639 - 12644


Carbon-Oxygen Lyases, Cells, Cultured, DNA Polymerase beta, DNA Repair, DNA Replication, DNA-(Apurinic or Apyrimidinic Site) Lyase, Deoxyribonuclease IV (Phage T4-Induced), Endodeoxyribonucleases, Flap Endonucleases, Humans, Precipitin Tests, Proliferating Cell Nuclear Antigen