title: 8-OxoA inhibits the incision of an AP site by the DNA glycosylases Fpg, Nth and the AP endonuclease HAP1.
abstract: Ionizing radiation induces clustered DNA damage sites, whereby two or more individual DNA lesions are formed within one or two helical turns of DNA by a single radiation track. A subset of DNA clustered damage sites exist in which the lesions are located in tandem on the same DNA strand. Recent studies have established that two closely opposed lesions impair the repair machinery of the cell, but few studies have investigated the processing of tandem lesions. In this study, synthetic double-stranded oligonucleotides were synthesized to contain 8-oxoA and an AP site in tandem, separated by up to four bases in either a 5' or 3' orientation. The influence 8-oxoA has on the incision of the AP site by the E. coli glycosylases Fpg and Nth protein and the human AP endonuclease HAP1 was assessed. 8-OxoA has little or no effect on the efficiency of incision of the AP site by Nth protein; however, the efficiency of incision of the AP site by Fpg protein is reduced in the presence of 8-oxoA even up to a four-base separation in both the 5' and 3' orientations. 8-OxoA influences the efficiency of HAP1 incision of the AP site only when it is 3' to the AP site and separated by up to two bases. This study demonstrates that the initial stages of base excision repair can be impaired by the presence of a second base lesion in proximity to an AP site on the same DNA strand. This impairment could have biological consequences, such as mutation induction, if the AP site is present at replication.
authors.affiliation: Medical Research Council, Radiation and Genome Stability Unit, Harwell, Didcot, Oxfordshire, OX11 0RD, United Kingdom. m.lomax@har.mrc.ac.uk
authors.forename: Martine E
authors.initials: ME
authors.lastname: Lomax
authors.forename: Henrik
authors.initials: H
authors.lastname: Salje
authors.forename: Siobhan
authors.initials: S
authors.lastname: Cunniffe
authors.forename: Peter
authors.initials: P
authors.lastname: O'Neill
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000528:radiation effects; D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000737:chemistry* / Q000528:radiation effects; D043382:DNA-Formamidopyrimidine Glycosylase / Q000737:chemistry* / Q000528:radiation effects; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000737:chemistry* / Q000528:radiation effects; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000528:radiation effects; D008969:Molecular Sequence Data; D011687:Purines / Q000737:chemistry / Q000528:radiation effects; D011743:Pyrimidines / Q000737:chemistry / Q000528:radiation effects; D011829:Radiation Dosage; D013329:Structure-Activity Relationship
chemical_list: D029968:Escherichia coli Proteins; D011687:Purines; D011743:Pyrimidines; C002992:8-hydroxyadenine; D004247:DNA; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D000225:Adenine; C030986:pyrimidine; C030985:purine