title: Selective enzymatic cleavage and labeling for sensitive capillary electrophoresis laser-induced fluorescence analysis of oxidized DNA bases.
abstract: Oxidatively generated DNA damage is considered to be a significant contributing factor to cancer, aging, and age-related human diseases. It is important to detect oxidatively generated DNA damage to understand and clinically diagnosis diseases caused by oxidative damage. In this study, using selective enzymatic cleavage and quantum dot (QD) labeling, we developed a novel capillary electrophoresis-laser induced fluorescence method for the sensitive detection of oxidized DNA bases. First, oxidized DNA bases are recognized and removed by one DNA base excision repair glycosylase, leaving apurinic and apyrimidinic sites (AP sites) at the oxidized positions. The AP sites are further excised by the AP nicking activity of the chosen glycosylase, generating a nucleotide gap with 5'- and 3'- phosphate groups. After dephosphorylation with one alkaline phosphatase, a biotinylated ddNTP is introduced into the nucleotide space within the DNA strand by DNA polymerase I. The biotin-tagged DNA is further labeled with a QD-streptavidin conjugate via non-covalent interactions. The DNA-bound QD is well-separated from excess DNA-unbound QD by highly efficient capillary electrophoresis and is sensitively detected by online coupled laser-induced fluorescence analysis. Using this method, we can assess the trace levels of oxidized DNA bases induced by the Fenton reaction and UV irradiation. Interestingly, the use of the formamidopyrimidine glycosylase (FPG) protein and endonuclease VIII enables the detection of oxidized purine and pyrimidine bases, respectively. Using the synthesized standard DNA, the approach has low limits of detection of 1.1×10(-19)mol in mass and 2.9pM in concentration.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
authors.forename: Cuiping
authors.initials: C
authors.lastname: Li
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China. Electronic address: hlwang@rcees.ac.cn.
authors.forename: Hailin
authors.initials: H
authors.lastname: Wang
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000379:methods* / Q000592:standards*; D004247:DNA / Q000032:analysis* / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase / Q000378:metabolism; D019075:Electrophoresis, Capillary; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005453:Fluorescence; D006801:Humans; D057230:Limit of Detection; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D010084:Oxidation-Reduction; D014466:Ultraviolet Rays
chemical_list: D029968:Escherichia coli Proteins; D004247:DNA; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase
keywords: Capillary electrophoresis laser-induced fluorescence (CE-LIF); Formamidopyrimidine glycosylase (FPG); Oxidized DNA bases; Quantum dot (QD)