Polymerase blockage and misincorporation of dNTPs opposite the ethylene dibromide-derived DNA adducts S-[2-(N7-guanyl)ethyl]glutathione, S-[2-(N2-guanyl)ethyl]glutathione, and S-[2-(O6-guanyl)ethyl]glutathione. 1998

M S Kim, and F P Guengerich
Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.

The carcinogen ethylene dibromide (EDB) has been shown to cause glutathione (GSH)-dependent base-substitution mutations, especially GC to AT transitions, in a variety of bacterial and eukaryotic systems. The known DNA adducts S-[2-(N7-guanyl)ethyl]GSH, S-[2-(N2-guanyl)ethyl]GSH, and S-[2-(O6-guanyl)ethyl]GSH were individually placed at a site in a single oligonucleotide. Polymerase extension studies were carried out using Escherichia coli polymerase I exo- (Klenow fragment, Kf-) and polymerase II exo- (pol II-), bacteriophage T7 polymerase exo-, and human immunodeficiency virus-1 reverse transcriptase in order to characterize misincorporation events. Even though extension was not as efficient as with the nonadducted template, some fully extended primers were observed with the template containing S-[2-(N7-guanyl)ethyl]GSH using all of these polymerases. dCTP was the most preferred nucleotide incorporated opposite S-[2-(N7-guanyl)ethyl]GSH by most of polymerases examined; however, dTTP incorporation was observed opposite S-[2-(N7-guanyl)ethyl]GSH with pol II-. Both S-[2-(N2-guanyl)ethyl]GSH and S-[2-(O6-guanyl)ethyl]GSH strongly blocked replication by all polymerases. Only dATP and dGTP were incorporated opposite S-[2-(N2-guanyl)ethyl]GSH by both Kf- and pol II-. S-[2-(O6-Guanyl)ethyl]GSH was shown to strongly code for dATP incorporation by Kf-. With pol II-, dTTP was incorporated opposite S-[2-(O6-guanyl)ethyl]GSH. In conclusion, all three GSH-guanyl adducts derived from the carcinogen EDB blocked the polymerases and were capable of miscoding.

UI MeSH Term Description Entries
D004247 DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004259 DNA-Directed DNA Polymerase DNA-dependent DNA polymerases found in bacteria, animal and plant cells. During the replication process, these enzymes catalyze the addition of deoxyribonucleotide residues to the end of a DNA strand in the presence of DNA as template-primer. They also possess exonuclease activity and therefore function in DNA repair. DNA Polymerase,DNA Polymerases,DNA-Dependent DNA Polymerases,DNA Polymerase N3,DNA Dependent DNA Polymerases,DNA Directed DNA Polymerase,DNA Polymerase, DNA-Directed,DNA Polymerases, DNA-Dependent,Polymerase N3, DNA,Polymerase, DNA,Polymerase, DNA-Directed DNA,Polymerases, DNA,Polymerases, DNA-Dependent DNA
D005978 Glutathione A tripeptide with many roles in cells. It conjugates to drugs to make them more soluble for excretion, is a cofactor for some enzymes, is involved in protein disulfide bond rearrangement and reduces peroxides. Reduced Glutathione,gamma-L-Glu-L-Cys-Gly,gamma-L-Glutamyl-L-Cysteinylglycine,Glutathione, Reduced,gamma L Glu L Cys Gly,gamma L Glutamyl L Cysteinylglycine
D015946 Ethylene Dibromide An effective soil fumigant, insecticide, and nematocide. In humans, it causes severe burning of skin and irritation of the eyes and respiratory tract. Prolonged inhalation may cause liver necrosis. It is also used in gasoline. Members of this group have caused liver and lung cancers in rodents. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985), 1,2-dibromoethane may reasonably be anticipated to be a carcinogen. 1,2-Dibromoethane,Dowfume W 85,Dowfume W85,Ethylene Bromide,Ethylene Dibromides,sym-Dibromoethane,1,2 Dibromoethane,Bromide, Ethylene,Dibromide, Ethylene,Dibromides, Ethylene,sym Dibromoethane
D018736 DNA Adducts The products of chemical reactions that result in the addition of extraneous chemical groups to DNA. DNA Adduct,Adduct, DNA,Adducts, DNA

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