title: Are endogenous clustered DNA damages induced in human cells?
abstract: Although clustered DNA damages are induced in cells by ionizing radiation and can be induced artifactually during DNA isolation, it was not known if they are formed in unirradiated cells by normal oxidative metabolism. Using high-sensitivity methods of quantitative gel electrophoresis, electronic imaging, and number average length analysis, we found that two radiosensitive human cell lines (TK6 and WI-L2-NS) accumulated Fpg-oxidized purine clusters and Nth-oxidized pyrimidine clusters but not Nfo-abasic clusters. However, four repair-proficient human lines (MOLT 4, HL-60, WTK1, and 28SC) did not contain significant levels (<5/Gbp) of any cluster type. Cluster levels were independent of p53 status. Measurement of glycosylase levels in 28SC, TK6, and WI-L2-NS cells suggested that depressed hOGG1 and hNth activities in TK6 and WI-L2-NS could be related to oxybase cluster accumulation. Thus, individuals with DNA repair enzyme deficiencies could accumulate potentially cytotoxic and mutagenic clustered DNA damages. The absence of Nfo-detected endogenous clusters in any cells examined suggests that abasic clusters could be a signature of cellular ionizing radiation exposure.
authors.affiliation: Department of Biology, Brookhaven National Laboratory, Upton, NY 11973-5000, USA.
authors.forename: Paula V
authors.initials: PV
authors.lastname: Bennett
authors.forename: Nela S
authors.initials: NS
authors.lastname: Cintron
authors.forename: Laurent
authors.initials: L
authors.lastname: Gros
authors.forename: Jacques
authors.initials: J
authors.lastname: Laval
authors.forename: Betsy M
authors.initials: BM
authors.lastname: Sutherland
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D045647:DNA Glycosylases / Q000378:metabolism; D004260:DNA Repair; D004586:Electrophoresis; D004926:Escherichia coli / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D009153:Mutagens; D009841:Oligonucleotides / Q000737:chemistry; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011687:Purines / Q000737:chemistry; D011743:Pyrimidines / Q000737:chemistry; D011770:Pyruvate Kinase / Q000378:metabolism; D011839:Radiation, Ionizing; D012680:Sensitivity and Specificity; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D009153:Mutagens; D009841:Oligonucleotides; D011687:Purines; D011743:Pyrimidines; D016159:Tumor Suppressor Protein p53; D004247:DNA; D011770:Pyruvate Kinase; D045647:DNA Glycosylases