Formation of DNA−Protein Cross-Links Between γ-Hydroxypropanodeoxyguanosine and EcoRI

The toxicity of acrolein, an alpha,beta-unsaturated aldehyde produced during lipid peroxidation, is attributable to its high reactivity toward DNA and cellular proteins. The major acrolein-DNA adduct, gamma-hydroxypropano-2'-deoxyguanosine (gamma-HOPdG), ring opens to form a reactive N(2)-oxopropyl moiety that cross-links to DNA and proteins. We demonstrate the ability of gamma-HOPdG in a duplex oligonucleotide to cross-link to a protein (EcoRI) that specifically interacts with DNA at a unique sequence. The formation of a cross-link to EcoRI was dependent on the intimate binding of the enzyme to its gamma-HOPdG-modified recognition site. Interestingly, the cross-link did not restrict the ability of EcoRI to cleave DNA substrates. However, stabilization of the cross-link by reduction of the Schiff base linkage resulted in loss of enzyme activity. This work indicates that the gamma-HOPdG-EcoRI cross-link is in equilibrium with free oligonucleotide and enzyme. Reversal of cross-link formation allows EcoRI to effect enzymatic cleavage of competitor oligonucleotides.