Stereospecific Formation of Interstrand Carbinolamine DNA Cross-Links by Crotonaldehyde- and Acetaldehyde-Derived α-CH₃-γ-OH-1,N²-Propano-2‘-deoxyguanosine Adducts in the 5‘-CpG-3‘ Sequence

Abstract

The crotonaldehyde- and acetaldehyde-derived R- and S-alpha-CH3-gamma-OH-1,N2-propanodeoxyguanosine adducts were monitored in single-stranded and duplex oligodeoxynucleotides using NMR spectroscopy. In both instances, the cis and trans diastereomers of the alpha-CH3 and gamma-OH groups underwent slow exchange, with the trans diastereomers being favored. In single-stranded oligodeoxynucleotides, the aldehyde intermediates were not detected spectroscopically, but their presence was revealed through the formation of N-terminal conjugates with the tetrapeptide KWKK. When annealed into 5'-d(GCTAGCXAGTCC)-3'.5'-d(GGACTCYCTAGC)-3' containing the 5'-CpG-3' sequence context (X = R- or S-alpha-CH3-gamma-13C-OH-PdG; Y = 15N2-dG) at pH 7, partial opening of the R- or S-alpha-CH3-gamma-13C-OH-PdG adducts to the corresponding N2-(3-oxo-1-methyl-propyl)-dG aldehydes was observed at temperatures below the T(m) of the duplexes. These aldehydes equilibrated with their geminal diol hydrates; higher temperatures favored the aldehydes. When annealed opposite T, the S-alpha-CH3-gamma-13C-OH-PdG adduct was stable. At 37 degrees C, an interstrand DNA cross-link was observed spectroscopically only for the R-alpha-CH3-gamma-OH-PdG adduct. Molecular modeling predicted that the interstrand cross-link formed by the R-alpha-CH3-gamma-OH-PdG adduct introduced less disruption into the duplex structure than did the cross-link arising from the S-alpha-CH3-gamma-OH-PdG adduct, due to differing orientations of the R- and S-CH3 groups. Modeling also predicted that the alpha-methyl group of the aldehyde arising from the R-alpha-CH3-gamma-OH-PdG adduct is oriented in the 3'-direction in the minor groove, facilitating cross-linking. In contrast, the alpha-methyl group of the aldehyde arising from the S-alpha-CH3-gamma-OH-PdG adduct is oriented in the 5'-direction within the minor groove, potentially hindering cross-linking. NMR revealed that for the R-alpha-CH3-gamma-OH-PdG adduct, the carbinolamine form of the cross-link was favored in duplex DNA with the imine (Schiff base) form of the cross-link remaining below the level of spectroscopic detection. Molecular modeling predicted that the carbinolamine linkage maintained Watson-Crick hydrogen bonding at both of the tandem C.G base pairs. Dehydration of the carbinolamine cross-link to an imine, or cyclization of the latter to form a pyrimidopurinone cross-link, required disruption of Watson-Crick hydrogen bonding at one or both of the cross-linked base pairs.

Interstrand DNA Cross-Links Induced by α,β-Unsaturated Aldehydes Derived from Lipid Peroxidation and Environmental Sources

“…64 These results were consistent with modeling of the native cross-links. 50 Lao and Hecht also concluded that the pyrimidopurinone cross-link arising from the 6R stereochemistry exhibited a more favorable orientation of the C6 CH 3 group. 20 Additional studies of the 6S diastereomer 12 were performed at pH 9.3.…”

“…A challenge was the preparation of stereochemically-defined amino diols for the crotonaldehyde (31,32) and 4-HNE adducts (33)(34)(35)(36) (Figure 2). [49][50][51][52] This strategy could not be applied to oligodeoxynucleotides containing α-OH-PdG (10), which were prepared using the modified phosphoramidite 25. 53,54 Interstrand Cross-linking by γ-OH-PdG…”

“…20 Although the cross-link could be reduced, NMR failed to detect the imine linkage in duplex DNA (Figure 8). 57 Using isotopically labeled adducts, 50 it was established that the carbinolamine form of the 6R cross-link was the only detectable cross-link species present in duplex DNA. As for the γ-OH-PdG adduct, modeling revealed that the carbinolamine linkage maintained Watson-Crick bonding at the cross-linked base pairs.…”

Analysis of Crotonaldehyde- and Acetaldehyde-Derived 1,N2-Propanodeoxyguanosine Adducts in DNA from Human Tissues Using Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry

“…This indicates that the formation of adduct 2 from acetaldehyde does not proceed through crotonaldehyde, but through N 2 -ethylidene-dGuo (3) (7). In duplex DNA, adduct 2 exits in equilibrium with its ring-opened aldehyde form (11) and can lead to the formation of interstrand cross-links and DNA-protein cross-links (7,12,13).…”

Replication-Coupled Repair of Crotonaldehyde/Acetaldehyde-Induced Guanine−Guanine Interstrand Cross-Links and Their Mutagenicity

“…have been characterized in reactions with DNA of other related compounds such as acrolein and malondialdehyde (7)(8)(9)(10).…”