title: Site-specific d(GpG) intrastrand cross-links formed by dinuclear platinum complexes. Bending and NMR studies.
abstract: The novel platinum drugs [{trans-PtCl(NH3)2}2H2N(CH2)nNH2]2+ (1,1/t,t) are currently undergoing preclinical development. The bifunctional DNA binding of these agents allows comparison with that of cisplatin [Farrell et al. (1995) Biochemistry, 34, 15480]. The major DNA lesion of cisplatin, the 1,2-d(GpG) intrastrand adduct, produces a rigid, directed bend 30-35 degrees into the major groove of DNA. We have now completed a structural analysis of the corresponding adduct formed with the dinuclear complexes. Gel retardation assays on 15-22 bp oligonucleotides containing a central d(TG*G*T) site show that the (Pt,Pt)-intrastrand adducts result in a flexible nondirectional bend. This bend is essentially independent of chain length (n = 2, 4, 6). Chemical reactivity assays indicated a hypersensitivity of the thymine 5' to the adduct and an enhanced sensitivity of the 3'-thymine to OsO4. 2D 1H NMR studies on a d(TG1G2T) adduct of [{trans-PtCl(NH3)2}2H2N(CH2)6NH2]2+ have delineated the structural features responsible for these observations. In contrast to the cisplatin adduct, which displays a 100% N-type sugar of the 5'-G and an anti base conformation of the platinated bases in both solid state and solution, the dinuclear adduct does not display the typical N-type sugar pucker. The base orientations are anti (5'-T), anti (G1), anti/syn (G2), and anti (3'-T) while the sugar conformations are N, S/N, N, and S, respectively. The 5'-T remains stacked with its guanine neighbor while the 3'-T becomes unstacked, a reverse of the situation observed for cis-DDP.
authors.affiliation: Institute of Biophysics, Academy of Sciences, Brno, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Kaspárková
authors.forename: K J
authors.initials: KJ
authors.lastname: Mellish
authors.forename: Y
authors.initials: Y
authors.lastname: Qu
authors.forename: V
authors.initials: V
authors.lastname: Brabec
authors.forename: N
authors.initials: N
authors.lastname: Farrell
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry*; D001483:Base Sequence; D001665:Binding Sites; D003432:Cross-Linking Reagents / Q000737:chemistry*; D018736:DNA Adducts / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D009944:Organoplatinum Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D018736:DNA Adducts; D009838:Oligodeoxyribonucleotides; D009944:Organoplatinum Compounds