title: Pre-steady-state fluorescence analysis of damaged DNA transfer from human DNA glycosylases to AP endonuclease APE1.
abstract: BACKGROUND
  DNA glycosylases remove the modified, damaged or mismatched bases from the DNA by hydrolyzing the N-glycosidic bonds. Some enzymes can further catalyze the incision of a resulting abasic (apurinic/apyrimidinic, AP) site through β- or β,δ-elimination mechanisms. In most cases, the incision reaction of the AP-site is catalyzed by special enzymes called AP-endonucleases.
  
  
  METHODS
  Here, we report the kinetic analysis of the mechanisms of modified DNA transfer from some DNA glycosylases to the AP endonuclease, APE1. The modified DNA contained the tetrahydrofurane residue (F), the analogue of the AP-site. DNA glycosylases AAG, OGG1, NEIL1, MBD4(cat) and UNG from different structural superfamilies were used.
  
  
  RESULTS
  We found that all DNA glycosylases may utilise direct protein-protein interactions in the transient ternary complex for the transfer of the AP-containing DNA strand to APE1.
  
  
  CONCLUSIONS
  We hypothesize a fast "flip-flop" exchange mechanism of damaged and undamaged DNA strands within this complex for monofunctional DNA glycosylases like MBD4(cat), AAG and UNG. Bifunctional DNA glycosylase NEIL1 creates tightly specific complex with DNA containing F-site thereby efficiently competing with APE1. Whereas APE1 fast displaces other bifunctional DNA glycosylase OGG1 on F-site thereby induces its shifts to undamaged DNA regions.
  
  
  CONCLUSIONS
  Kinetic analysis of the transfer of DNA between human DNA glycosylases and APE1 allows us to elucidate the critical step in the base excision repair pathway.
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Novosibirsk 630090, Russia.
authors.forename: Alexandra A
authors.initials: AA
authors.lastname: Kuznetsova
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Novosibirsk 630090, Russia; Department of Natural Sciences, Novosibirsk State University, Novosibirsk 630090, Russia. Electronic address: nikita.kuznetsov@niboch.nsc.ru.
authors.forename: Nikita A
authors.initials: NA
authors.lastname: Kuznetsov
authors.affiliation: Groupe «Réparation de l'ADN», Université Paris-Sud XI, UMR8200 CNRS, Institut Gustave Roussy, Villejuif Cedex F-94805, France.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Ishchenko
authors.affiliation: Groupe «Réparation de l'ADN», Université Paris-Sud XI, UMR8200 CNRS, Institut Gustave Roussy, Villejuif Cedex F-94805, France.
authors.forename: Murat K
authors.initials: MK
authors.lastname: Saparbaev
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Novosibirsk 630090, Russia; Department of Natural Sciences, Novosibirsk State University, Novosibirsk 630090, Russia. Electronic address: fedorova@niboch.nsc.ru.
authors.forename: Olga S
authors.initials: OS
authors.lastname: Fedorova
mesh_terms: D004249:DNA Damage; D045647:DNA Glycosylases / Q000737:chemistry*; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000737:chemistry*; D005453:Fluorescence; D006801:Humans
chemical_list: D045647:DNA Glycosylases; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase
keywords: AP endonuclease; Base excision repair; Coordination of DNA repair process; DNA glycosylase; Protein–protein interaction