title: Regulation of WRN helicase activity in human base excision repair.
abstract: Werner syndrome patients are deficient in the Werner protein (WRN), which is a multifunctional nuclear protein possessing 3'-5' exonuclease and ATP-dependent helicase activities. Studies of Werner syndrome cells and biochemical studies of WRN suggest that WRN plays a role in several DNA metabolic pathways. WRN interacts with DNA polymerase beta (pol beta) and stimulates pol beta strand displacement synthesis on a base excision repair (BER) intermediate in a helicase-dependent manner. In this report, we examined the effect of the major human apurinic/apyrimidinic endonuclease (APE1) and of pol beta on WRN helicase activity. The results show that WRN alone is able to unwind several single strand break BER intermediates. However, APE1 inhibits WRN helicase activity on these intermediates. This inhibition is likely due to the binding of APE1 to nicked apurinic/apyrimidinic sites, suggesting that APE1 prevents the promiscuous unwinding of BER intermediates. This inhibitory effect was relieved by the presence of pol beta. A model involving the pol beta-mediated hand-off of WRN protein is proposed based on these results.
authors.affiliation: Department of Life Sciences, University of Ulsan, Ulsan 680-749, Korea.
authors.forename: Byungchan
authors.initials: B
authors.lastname: Ahn
authors.forename: Jeanine A
authors.initials: JA
authors.lastname: Harrigan
authors.forename: Fred E
authors.initials: FE
authors.lastname: Indig
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004265:DNA Helicases / Q000378:metabolism*; D019951:DNA Polymerase beta / Q000737:chemistry / Q000378:metabolism; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005090:Exodeoxyribonucleases; D015971:Gene Expression Regulation, Enzymologic; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D009154:Mutation; D009691:Nucleic Acid Denaturation; D011485:Protein Binding; D053484:RecQ Helicases; D014898:Werner Syndrome / Q000378:metabolism; D000071657:Werner Syndrome Helicase
chemical_list: D000255:Adenosine Triphosphate; D004247:DNA; D005982:Glutathione Transferase; D019951:DNA Polymerase beta; D005090:Exodeoxyribonucleases; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase