title: New insights in the removal of the hydantoins, oxidation product of pyrimidines, via the base excision and nucleotide incision repair pathways.
abstract: BACKGROUND
  Oxidative damage to DNA, if not repaired, can be both miscoding and blocking. These genetic alterations can lead to mutations and/or cell death, which in turn cause cancer and aging. Oxidized DNA bases are substrates for two overlapping repair pathways: base excision (BER) and nucleotide incision repair (NIR). Hydantoin derivatives such as 5-hydroxyhydantoin (5OH-Hyd) and 5-methyl-5-hydroxyhydantoin (5OH-5Me-Hyd), major products of cytosine and thymine oxidative degradation pathways, respectively, have been detected in cancer cells and ancient DNA. Hydantoins are blocking lesions for DNA polymerases and excised by bacterial and yeast DNA glycosylases in the BER pathway. However little is known about repair of pyrimidine-derived hydantoins in human cells.
  
  
  RESULTS
  Here, using both denaturing PAGE and MALDI-TOF MS analyses we report that the bacterial, yeast and human AP endonucleases can incise duplex DNA 5' next to 5OH-Hyd and 5OH-5Me-Hyd thus initiating the NIR pathway. We have fully reconstituted the NIR pathway for these lesions in vitro using purified human proteins. Depletion of Nfo in E. coli and APE1 in HeLa cells abolishes the NIR activity in cell-free extracts. Importantly, a number of redundant DNA glycosylase activities can excise hydantoin residues, including human NTH1, NEIL1 and NEIL2 and the former protein being a major DNA glycosylase activity in HeLa cells extracts.
  
  
  CONCLUSIONS
  This study demonstrates that both BER and NIR pathways can compete and/or back-up each other to remove hydantoin DNA lesions in vivo.
authors.affiliation: Groupe Réparation de l'ADN, CNRS UMR8200, Université Paris-Sud, Institut de Cancérologie Gustave Roussy, Villejuif, France.
authors.forename: Modesto
authors.initials: M
authors.lastname: Redrejo-Rodríguez
authors.forename: Christine
authors.initials: C
authors.lastname: Saint-Pierre
authors.forename: Sophie
authors.initials: S
authors.lastname: Couve
authors.forename: Abdelghani
authors.initials: A
authors.lastname: Mazouzi
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Ishchenko
authors.forename: Didier
authors.initials: D
authors.lastname: Gasparutto
authors.forename: Murat
authors.initials: M
authors.lastname: Saparbaev
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000235:genetics* / Q000378:metabolism*; D045647:DNA Glycosylases / Q000378:metabolism; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006827:Hydantoins / Q000378:metabolism*; D007700:Kinetics; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D011743:Pyrimidines / Q000378:metabolism*; D013941:Thymine / Q000031:analogs & derivatives / Q000378:metabolism; D014508:Urea / Q000378:metabolism
chemical_list: D006827:Hydantoins; D009838:Oligodeoxyribonucleotides; D011743:Pyrimidines; C029389:thymine glycol; D014508:Urea; D004247:DNA; D045647:DNA Glycosylases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; C030986:pyrimidine; D013941:Thymine