title: GA and AG sequences of DNA react with cisplatin at comparable rates.
abstract: The sequence selectivity of the antitumor drug cisplatin (cis-[PtCl(2)(NH(3))(2)] (1)) between the 5'-AG-3' and 5'-GA-3' sites of DNA has been a matter of discussion for more than twenty years. In this work, we compared the reactivity of GA and AG sequences of DNA towards the aquated forms of cisplatin (cis-[PtCl(NH(3))(2)(H(2)O)](+) (2), cis-[Pt(NH(3))(2)(H(2)O)(2)](2+) (3), and cis-[Pt(OH)(NH(3))(2)(H(2)O)](+) (4)) using two sets of experiments. In the first, we investigated a DNA hairpin, whose duplex stem contained a TGAT sequence as the single reactive site, and determined the individual rate constants of platination with 2 and 3 for G and A in acidic solution. The rate constants at 20 degrees C in 0.1M NaClO(4) at pH 4.5+/-0.1 were 0.09(4) M(-1)s(-1) (G) and 0.11(3) M(-1)s(-1) (A) for 2, and 9.6(1) M(-1)s(-1) (G) and 1.7(1) M(-1)s(-1) (A) for 3. These values are similar to those obtained previously for an analogous hairpin that contained a TAGT sequence. The monoadducts formed with 2 by both GA purines are extremely long-lived, partly as a result of the slow hydrolysis of the chloro monoadduct at A, and partly because of the very low chelation rate (1.4 x 10(-5)s(-1) at 20 degrees C) of the aqua monoadduct on the guanine. In the second set of experiments, we incubated pure or enriched samples of 1, 2, 3, or 4 for 18-64 h at 25 degrees C with a 19 base pair (bp) DNA duplex, whose radiolabeled top strand contained one GA and one AG sequence as the only reactive sites. Quantification of the number of GA and AG cross-links afforded a ratio of about two in favor of AG, irrespective of the nature of the leaving ligands. These results disagree with a previous NMR spectroscopy study, and indicate that GA sequences of DNA are substantially more susceptible to attack by cisplatin than previously thought.
authors.affiliation: Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Université René Descartes, CNRS, UMR 8601, 45 rue des Saints-Pères, 75270 Paris, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Monjardet-Bas
authors.forename: Sophie
authors.initials: S
authors.lastname: Bombard
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Chottard
authors.forename: Jirí
authors.initials: J
authors.lastname: Kozelka
mesh_terms: D000225:Adenine / Q000737:chemistry; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry; D001483:Base Sequence; D002614:Chelating Agents / Q000737:chemistry; D002945:Cisplatin / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D003435:Crotalid Venoms / Q000201:enzymology; D004247:DNA / Q000737:chemistry*; D018736:DNA Adducts / Q000737:chemistry*; D005092:Exonucleases / Q000378:metabolism; D006147:Guanine / Q000737:chemistry; D007700:Kinetics; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D017422:Sequence Analysis, DNA / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D000970:Antineoplastic Agents; D002614:Chelating Agents; D003432:Cross-Linking Reagents; D003435:Crotalid Venoms; D018736:DNA Adducts; D009841:Oligonucleotides; C057270:cisplatin-DNA adduct; D014867:Water; D010984:Platinum; D006147:Guanine; D004247:DNA; D005092:Exonucleases; C022650:spleen exonuclease; D000225:Adenine; D002945:Cisplatin