FORMATION AND STABILITY OF ACETALDEHYDE-INDUCED CROSS-LINKS BETWEEN POLYLYSINE AND POLY-DEOXYGUANOSINE

The amino acid residue and nucleoside specificity of acetaldehyde-indu ced DNA-protein crosslinks (DPXLs) were studied using a modified filte r binding assay. A 40% inhibition of acetaldehyde-induced pUC13 plasmi d DNA-calf thymus histone crosslink formation was achieved by addition of 50 mM lysine (free base), while arginine was unable to affect cros slink formation at concentrations to 150 mM. Polymers (5-mers) of lysi ne (poly-lys(5)) were able to substitute for histones in acetaldehyde- induced plasmid crosslink formation, being equally effective at equimo lar concentrations. Homopolymers (6-mers) of deoxyguanosine (poly-dG(6 )) (but not deoxyadenosine, deoxycytidine or thymidine) served as an e fficient substrate for acetaldehyde-induced DPXL formation, using eith er calf thymus histones or poly-lys(5) as the protein source. Acetalde hyde-induced crosslinks between poly-dG(6) and poly-lys(5) were formed rapidly, but were unstable at 37 degrees C (a half-life or 1.5-2 h). Stability of these crosslinks was unaffected by pH at a range of 5.5-9 .0 at 37 degrees C for 2 h. Results presented here suggest that unstab le complexes of deoxyguanosine and lysine constitute a major portion o f the DPXLs formed by acetaldehyde in vitro.