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

Abstract

ConspectusSignificant levels of the 1,N 2 -γ-hydroxypropano-dG adducts of the α,β-unsaturated aldehydes acrolein, crotonaldehyde, and 4-hydroxy-2E-nonenal (HNE) have been identified in human DNA, arising from both exogenous and endogenous exposure. They yield interstrand DNA cross-links between guanines in the neighboring C•G and G•C base pairs located in 5′-CpG-3′ sequences, as a result of opening of the 1,N 2 -γ-hydroxypropano-dG adducts to form reactive aldehydes that are positioned within the minor groove of duplex DNA. Using a combination of chemical, spectroscopic, and computational methods, we have elucidated the chemistry of cross-link formation in duplex DNA. NMR spectroscopy revealed that, at equilibrium, the acrolein and crotonaldehyde cross-links consist primarily of interstrand carbinolamine linkages between the exocyclic amines of the two guanines located in the neighboring C•G and G•C base pairs located in 5′-CpG-3′ sequences, that maintain the Watson-Crick hydrogen bonding of the cross-linked base pairs. The ability of crotonaldehyde and HNE to form interstrand cross-links depends upon their common relative stereochemistry at the C6 position of the 1,N 2 -γ-hydroxypropano-dG adduct. The stereochemistry at this center modulates the orientation of the reactive aldehyde within the minor groove of the doublestranded DNA, either facilitating or hindering the cross-linking reactions; it also affects the stabilities of the resulting diastereoisomeric cross-links. The presence of these cross-links in vivo is anticipated to interfere with DNA replication and transcription, thereby contributing to the etiology of human disease. Reduced derivatives of these cross-links are useful tools for studying their biological processing. IntroductionThe α,β-unsaturated aldehydes (enals) acrolein, crotonaldehyde, and 4-hydroxynonenal (4-HNE) (Scheme 1) are endogenous byproducts of lipid peroxidation, arising as a consequence of oxidative stress. [1][2][3][4] Acrolein and crotonaldehyde exposures also occur from exogenous sources, e.g., cigarette smoke 5 and automobile exhaust. 6 Enals react with DNA nucleobases to give exocyclic adducts; they also react with proteins. 7 Addition of enals to dG involves Michael addition of the N 2 -amine to give N 2 -(3-oxopropyl)-dG adducts (1, 3-8), followed by * Michael P. Stone telephone, 615-322-2589; fax, 615-322-7591; michael.p The lipid peroxidation product 4-HNE afforded related dGadducts (13-16). 14 Identification of acrolein adducts of other nucleosides followed. 15,16 The principal acrolein adduct is γ-OH-PdG (9), 10,12 although the regioisomeric 6-hydroxypyrimido[1,2-a]purin-10(3H)-one (α-OH-PdG, 10) has also been observed. 12,17 The γ-OH-PdG adduct (9) exists as a mixture of C8-OH epimers. With crotonaldehyde, addition at N 2 -dG creates a stereocenter at C6. Of four possible products, the two with the trans relative configurations at C6 and C8 (11,12) are observed. 12,18 These are also formed through the reaction of dG with two equivalents of acetaldehyde. 5,19,20 The cor...

Nucleophilic properties of purine bases: inherent reactivity versus reaction conditions

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Structure-Function Relationships in Miscoding by Sulfolobus solfataricus DNA Polymerase Dpo4: GUANINE N2,N2-DIMETHYL SUBSTITUTION PRODUCES INACTIVE AND MISCODING POLYMERASE COMPLEXES

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