Mutation Spectra of S-(2-Hydroxy-3,4-epoxybutyl)glutathione: Comparison with 1,3-Butadiene and Its Metabolites in the Escherichia coli rpoB Gene

Abstract

S-(2-Hydroxy-3,4-epoxybutyl)glutathione (DEB-GSH conjugate) is formed from the reaction of 1,2:3,4-diepoxybutane (DEB) with glutathione (GSH), and the conjugate is considerably more mutagenic than several other butadiene-derived epoxides—including DEB—in Salmonella typhimurium TA1535 (Cho, S-H. et al., Chem. Res. Toxicol. 23, 1544–1546 (2010)). We previously identified six DNA adducts in the reaction of the DEB-GSH conjugate with nucleosides and calf thymus DNA and two DNA adducts in livers of mice and rats treated with DEB (Cho, S-H., and Guengerich, F.P., Chem. Res. Toxicol. 25, 706–712 (2012)). In order to define the role of GSH conjugation in 1,3-butadiene (BD) metabolism and characterize the mechanism of GSH transferase (GST)-enhanced mutagenicity of DEB, mutation spectra of BD and its metabolites in the absence and presence of GST/GSH and mouse liver microsomes were compared in the rpoB gene of Escherichia coli TRG8. The presence of GST considerably enhanced mutations. The mutation spectra derived from the DEB-GSH conjugate, the DEB/GST/GSH system, and the BD/mouse liver microsomes/GST/GSH system matched each other and were different from those derived from the other systems devoid of GSH. The major adducts in E. coli TRG8 cells treated with the DEB/GST/GSH system, the BD/mouse liver microsomes/GST/GSH system, or the DEB-GSH conjugate were S-[4-(N7-guanyl)-2,3-dihydroxybutyl]GSH, S-[4-(N3-adenyl)-2,3-dihydroxybutyl]GSH, and S-[4-(N6-deoxyadenosinyl)-2,3-dihydroxybutyl]GSH, indicating the presence of the GSH-containing DNA adducts in the systems. These results, along with the strong enhancement of mutagenicity by GST in this system, indicate the relevance of these GSH-containing DNA adducts.

Replication past the Butadiene Diepoxide-Derived DNA Adduct S-[4-(N6-Deoxyadenosinyl)-2,3-dihydroxybutyl]glutathione by DNA Polymerases

“…Both Pol T7 and, of more relevance, human Pol κ incorporated the correct T and incorrect C bases opposite N 6 dA-(OH) 2 butyl-GSH adduct, and translesion bypass beyond the N 6 dA-(OH) 2 butyl-GSH adduct by Pol T7 and Pol κ was error-prone. These results, coupled with our earlier findings, 26 indicate the relevance of GSH-containing adducts in A:T to G:C mutations produced by DEB, the oxidation product of BD.…”

“…26 The sequence of the rpoB gene including the major mutational hot spot (amino acid 512) induced by the DEB-GSH conjugate 26 was used for the 19-mer oligomer containing the N 6 dA-(OH) 2 butyl-GSH aor the N 6 dA-butanetriol adduct. For a qualitative comparison of the bypass efficiency past the N 6 dA-(OH) 2 butyl-GSH adduct by various DNA polymerases, primer extension assays were performed in the presence of all four dNTPs (Figure 1).…”

In Vivo Roles of Conjugation with Glutathione and O6-Alkylguanine DNA-Alkyltransferase in the Mutagenicity of the Bis-Electrophiles 1,2-Dibromoethane and 1,2,3,4-Diepoxybutane in Mice

“…57 In this test strain, the mutation spectra of GSH-enhanced systems differed from that obtained with DEB. 57 The DNA adduct S -[4- (N 6 -deoxyadenosinyl)-2,3-dihydroxybutyl]GSH was miscoding with human DNA polymerase κ (and bacteriophage DNA polymerase T7 exonuclease − ) but not with other DNA polymerases. 58 The DNA adducts S -[4- (N 6 -deoxyadenosinyl)-2,3-dihydroxybutyl]GSH and S -[4- (N 7 -guanyl)-2,3-dihydroxybutyl]GSH have been detected and quantitated in vivo in livers of rats and mice.…”

“…54–56 The GSH-DEB conjugate S -(2-hydroxy-3,4-epoxybutyl)GSH is 20-fold more mutagenic than DEB in the Salmonella typhimurium TA1535 base pair tester system. 56,57 In Escherichia coli TGR8, GST also increased the mutagenicity of DEB and for systems in which 1,3-butadiene was oxidized by P450s. 57 In this test strain, the mutation spectra of GSH-enhanced systems differed from that obtained with DEB.…”

“…56,57 In Escherichia coli TGR8, GST also increased the mutagenicity of DEB and for systems in which 1,3-butadiene was oxidized by P450s. 57 In this test strain, the mutation spectra of GSH-enhanced systems differed from that obtained with DEB. 57 The DNA adduct S -[4- (N 6 -deoxyadenosinyl)-2,3-dihydroxybutyl]GSH was miscoding with human DNA polymerase κ (and bacteriophage DNA polymerase T7 exonuclease − ) but not with other DNA polymerases.…”