title: Influence of DNA repair gene polymorphisms on the initial repair of MMS-induced DNA damage in human lymphocytes as measured by the alkaline comet assay.
abstract: We have applied the alkaline comet assay to study the functional impact of gene polymorphisms in base excision repair (APEX1 Asp148Glu, XRCC1 Arg194Trp, XRCC1 Arg399Gln) and homologous recombination repair (XRCC3 Thr241Met, NBS1 Glu185Gln), two pathways that play crucial roles in the repair of DNA damage induced by methylmethane sulphonate (MMS). We also examined the effect of polymorphisms in mismatch repair (MLH1 -93 A/G) and nucleotide excision repair (XPD Lys751Gln) as putative negative controls based on the limited roles of these pathways in MMS-induced repair. Phytohemagglutinin-stimulated peripheral lymphocytes from 52 healthy individuals were treated with MMS and allowed to repair for 0, 15, 40, or 120 min after a 6-min washing step. DNA damage was measured as a pseudo-percentage score (comparable to % tail DNA) converted from a total visual score calculated from the distribution of cells with different degrees of damage (normal, mild, moderate and severe). The repair was faster at the beginning of the observation period than towards the end, and was not complete after 2 hr. Presence of the APEX1 148Asp, XRCC3 241Met or NBS1 185Gln alleles were significantly associated with a high pseudo-percentage score (above median) at early time points, with the APEX1 effect being most prolonged (up to 40 min after washing, odds ratio 5.6, 95% confidence interval 2.0-15.5). No significant effects were seen with the XRCC1 Arg194Trp, XRCC1 Arg399Gln, MLH1 -93A/G and XPD Lys751Gln polymorphisms. Our results provide evidence for the functional nature of the variant alleles studied in the APEX1, XRCC3, and NBS1 genes.
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institute, 14157 Huddinge, Sweden.
authors.forename: Charlotta
authors.initials: C
authors.lastname: Ryk
authors.forename: Michael N
authors.initials: MN
authors.lastname: Routledge
authors.forename: James M
authors.initials: JM
authors.lastname: Allan
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Wild
authors.forename: Rajiv
authors.initials: R
authors.lastname: Kumar
authors.forename: Bo
authors.initials: B
authors.lastname: Lambert
authors.forename: Saimei
authors.initials: S
authors.lastname: Hou
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics; D002478:Cells, Cultured; D020552:Comet Assay / Q000379:methods*; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D005838:Genotype; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008741:Methyl Methanesulfonate / Q000494:pharmacology*; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics; D011110:Polymorphism, Genetic; D000076105:X-ray Repair Cross Complementing Protein 1; D051759:Xeroderma Pigmentosum Group D Protein / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; C112156:NBN protein, human; D009687:Nuclear Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; C110901:X-ray repair cross complementing protein 3; C000619371:XRCC1 protein, human; D008741:Methyl Methanesulfonate; D000070957:MutL Protein Homolog 1; D051759:Xeroderma Pigmentosum Group D Protein; C497292:ERCC2 protein, human