Structure/function analysis of the interaction of adenomatous polyposis coli with DNA polymerase beta and its implications for base excision repair

Biochemistry. 2007 Dec 11;46(49):13961-74. doi: 10.1021/bi701632e. Epub 2007 Nov 14.


Mutations in the adenomatous polyposis coli (APC) gene are associated with an early onset of colorectal carcinogenesis. Previously, we described a novel role for the APC polypeptide in base excision repair (BER). The single-nucleotide (SN) and long-patch (LP) BER pathways act to repair the abasic sites in DNA that are induced by stressors, such as spontaneous oxidation/reduction, alkylation, and hyperthermia. We have shown that APC interacts with DNA polymerase beta (Pol-beta) and flap endonuclease 1 (Fen-1) and blocks Pol-beta-directed strand-displacement synthesis. In this study, we have mapped the APC interaction site in Pol-beta and have found that Thr79, Lys81, and Arg83 of Pol-beta were critical for its interaction with APC. The Pol-beta protein (T79A/K81A/R83A) blocked strand-displacement DNA synthesis in which tetrahydrofuran was used as DNA substrate. We further showed that the APC-mediated blockage of LP-BER was due to inhibition of Fen-1 activity. Analysis of the APC-mediated blockage of SN-BER indicated that the interaction of APC with Pol-beta blocked SN-BER activity by inhibiting Pol-beta-directed deoxyribose phosphate lyase activity. Collectively, our findings indicate that APC blocked both Pol-beta-directed SN- and LP-BER pathways and increased sensitivity of cells to alkylation induced DNA damage.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenomatous Polyposis Coli Protein / genetics*
  • Amino Acid Sequence
  • Cell Line, Tumor
  • DNA Polymerase beta / chemistry*
  • DNA Polymerase beta / genetics
  • DNA Polymerase beta / physiology*
  • DNA Repair / physiology*
  • Humans
  • Methyl Methanesulfonate / pharmacology
  • Models, Molecular
  • Phosphorus-Oxygen Lyases / metabolism


  • Adenomatous Polyposis Coli Protein
  • Methyl Methanesulfonate
  • 5'-deoxyribose phosphate lyase
  • DNA Polymerase beta
  • Phosphorus-Oxygen Lyases