title: Structure/function analysis of the interaction of adenomatous polyposis coli with DNA polymerase beta and its implications for base excision repair.
abstract: 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.
authors.affiliation: Department of Anatomy and Cell Biology, UF Shands Cancer Center, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Balusu
authors.forename: Aruna S
authors.initials: AS
authors.lastname: Jaiswal
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Armas
authors.forename: Chanakya N
authors.initials: CN
authors.lastname: Kundu
authors.forename: Linda B
authors.initials: LB
authors.lastname: Bloom
authors.forename: Satya
authors.initials: S
authors.lastname: Narayan
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics*; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D019951:DNA Polymerase beta / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D004260:DNA Repair / Q000502:physiology*; D006801:Humans; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D008958:Models, Molecular; D019761:Phosphorus-Oxygen Lyases / Q000378:metabolism
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D008741:Methyl Methanesulfonate; C423906:5'-deoxyribose phosphate lyase; D019951:DNA Polymerase beta; D019761:Phosphorus-Oxygen Lyases