1,N-Deoxyguanosine Adducts of Acrolein, Crotonaldehyde, and trans-4-Hydroxynonenal Cross-link to Peptides via Schiff Base Linkage*

DNA-protein cross-links (DPCs) are formed upon exposure to a variety of chemical and physical agents and pose a threat to genomic integrity. In particular, acrolein and related aldehydes produce DPCs, although the chemical linkages for such cross-links have not been identified. Here, we report that oligodeoxynucleotides containing 1,N-deoxyguanosine adducts of acrolein, crotonaldehyde, and trans-4-hydroxynonenal can form cross-links with the tetrapeptide Lys-Trp-Lys-Lys. We concluded that complex formation is mediated by a Schiff base linkage because DNA-peptide complexes were covalently trapped following reduction with sodium cyanoborohydride, and pre-reduction of adducted DNAs inhibited complex formation. A previous NMR study demonstrated that duplex DNA catalyzes ring opening for the acrolein-derived -hydroxy-1,N-propanodeoxyguanosine adduct to yield an aldehydic function (de los Santos, C., Zaliznyak, T., and Johnson, F. (2001) J. Biol. Chem. 276, 9077–9082). Consistent with this earlier observation, the adducts under investigation were more reactive in duplex DNA than in singlestranded DNA, and we concluded that the ring-open aldehydic moiety is the induced tautomer in duplex DNA for adducts exhibiting high relative reactivity. Adducted DNA cross-linked to Arg-Trp-Arg-Arg and LysTrp-Lys-Lys with comparable efficiency, and N -acetylation of peptides dramatically inhibited trapping; thus, the reactive nucleophile is located at the N-terminal -amine of the peptide. These data suggest that Schiff base chemistry can mediate DPC formation in vivo following the formation of stable aldehyde-derived DNA adducts.