Mass spectrometric investigation of the sequence selectivity for adduction of heterocyclic aromatic amines on single‐strand oligonucleotides

Abstract

Heterocyclic aromatic amines (HAAs) generated during the cooking of meats are known to be genotoxic substances able to form covalent bonds with DNA bases after metabolic activation. This work aimed at the investigation of the influence of the local environment of nucleobases along the nucleotidic sequence on its modification induced by two different HAAs, namely 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), in order to identify possible sequences more susceptible to modification. A systematic study of the neighbouring base effect on the adduction was emphasized. Thus, PhIP and IQ adducts have been synthesized with various T-rich model single-strand oligonucleotides displaying different flanking bases (A, G, C or T) at the 3' or the 5' side of the targeted guanine, which allowed a comparison of the flanking base effects on adduction. Modified oligonucleotides were then analyzed by high-performance liquid chromatography (HPLC) coupled to electrospray ionization mass spectrometry. The localization of the modifications induced by PhIP or IQ along the oligonucleotide sequence was achieved by tandem mass spectrometry, and modification yields of the various model sequences were compared. Results indicate a favouring sequence context effect on the G-C8-IQ adduct formation with the sequence 5'GGG3'. Although higher than IQ, modification yields observed with PhIP showed a less obvious effect of the neighbouring base on the G-C8-PhIP adduct formation, with a preferential sequence 5'GGA/G/T3'.

Origin of Somatic Mutations in β-Catenin versus Adenomatous Polyposis Coli in Colon Cancer: Random Mutagenesis in Animal Models versus Nonrandom Mutagenesis in Humans

“…This is not absolutely accurate since HAA and other alkylating agents do show a modest sequence selectivity in terms of their formation and repair. However, the selectivity for HAA’s and small alkylating agents is not at CpG sequences. − DNA repair can also be impacted by sequence but the effect is relatively small and cannot explain the remarkable preference for CpG and CpApG sequences . As mentioned above, the frequency of truncating G → T transversions in APC is below what would be predicted due to random mutations and not elevated as predicted if HAA’s adducts were a cause of mutated APC (Table ).…”

Mass Spectrometry of Structurally Modified DNA

“…It was observed that IQ preferred 5′-GGG-3′ sequences, while PhIP preferred 5′-GGA/G/T-3′ trinucleotides, with the site of adduction being the center guanine base. 239 …”

“…238 Jamin et al utilized ESI-MS/MS to study the effects of different bases flanking on the 3′ or 5′ side of a guanine base on its reactivity towards heterocyclic aromatic amines, 2-amino-1methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3methylimidazo[4,5-f ]quinoline (IQ). 239 Model oligonucleotides (5′-TTTTTXGYTTTT-3′, where X and Y can be either C/ A/G/T) were incubated with activated HAAs, and the reaction mixtures were directly analyzed using HPLC-MS/MS. It was observed that IQ preferred 5′-GGG-3′ sequences, while PhIP preferred 5′-GGA/G/T-3′ trinucleotides, with the site of adduction being the center guanine base.…”

The analysis of DNA adducts: The transition from 32P-postlabeling to mass spectrometry

“…In 2008, Jamin et al [86] investigated the influence of the local environment and neighboring base effect on the adduction of HAAs, specifically PhIP and IQ on T-rich model single-strand oligonucleotides. Similarly, Chan et al [87] reported an electrospray ionization tandem mass spectrometry method for the identification and position mapping of unmodified and aristolochic acid modified (5′-TTTATT-3′, 5′-TTTGTT-3′ and 5′-TACATGTGT-3′) oligonucleotides.…”