Formation of S-[2-(N-Deoxyadenosinyl)ethyl]glutathione in DNA and Replication Past the Adduct by Translesion DNA Polymerases.

Sedgeman CA, Su Y, Guengerich FP
Chem Res Toxicol. 2017 30 (5): 1188-1196

PMID: 28395138 · PMCID: PMC5768145 · DOI:10.1021/acs.chemrestox.7b00022

1,2-Dibromoethane (DBE, ethylene dibromide) is a potent carcinogen due at least in part to its DNA cross-linking effects. DBE cross-links glutathione (GSH) to DNA, notably to sites on 2'-deoxyadenosine and 2'-deoxyguanosine ( Cmarik , J. L. , et al. ( 1991 ) J. Biol. Chem. 267 , 6672 - 6679 ). Adduction at the N6 position of 2'-deoxyadenosine (dA) had not been detected, but this is a site for the linkage of O-alkylguanine DNA alkyltransferase ( Chowdhury , G. , et al. ( 2013 ) Angew. Chem. Int. Ed. 52 , 12879 - 12882 ). We identified and quantified a new adduct, S-[2-(N-deoxyadenosinyl)ethyl]GSH, in calf thymus DNA using LC-MS/MS. Replication studies were performed in duplex oligonucleotides containing this adduct with human DNA polymerases (hPols) η, ι, and κ, as well as with Sulfolobus solfataricus Dpo4, Escherichia coli polymerase I Klenow fragment, and bacteriophage T7 polymerase. hPols η and ι, Dpo4, and Klenow fragment were able to bypass the adduct with only slight impedance; hPol η and ι showed increased misincorporation opposite the adduct compared to that of unmodified 2'-deoxyadenosine. LC-MS/MS analysis of full-length primer extension products by hPol η confirmed the incorporation of dC opposite S-[2-(N-deoxyadenosinyl)ethyl]GSH and also showed the production of a -1 frameshift. These results reveal the significance of N-dA GSH-DBE adducts in blocking replication, as well as producing mutations, by human translesion synthesis DNA polymerases.

MeSH Terms (9)

Animals Cattle Chromatography, Liquid DNA-Directed DNA Polymerase DNA Adducts DNA Replication Ethylene Dibromide Glutathione Tandem Mass Spectrometry

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