title: Marked dependence on carrier-ligand bulk but not on carrier-ligand chirality of the duplex versus single-strand forms of a DNA oligonucleotide with a series of G-Pt(II)-G intrastrand cross-links modeling cisplatin-DNA adducts.
abstract: The N7-Pt-N7 adjacent G,G intrastrand DNA cross-link responsible for cisplatin anticancer activity is dynamic, promotes local "melting" in long DNA, and converts many oligomer duplexes to single strands. For 5'-d(A1T2G3G4G5T6A7C8C9C10A11T12)-3' (G3), treatment of the (G3)2 duplex with five pairs of [LPt(H2O)2]2+ enantiomers (L = an asymmetric diamine) formed mixtures of LPt-G3 products (1 Pt per strand) cross-linked at G3,G4 or at G4,G5 in all cases. L chirality exerted little influence. For primary diamines L with bulk on chelate ring carbons (e.g., 1,2-diaminocyclohexane), the duplex was converted completely into single strands (G3,G4 coils and G4,G5 hairpins), exactly mirroring results for cisplatin, which lacks bulk. In sharp contrast, for secondary diamines L with bulk on chelate ring nitrogens (e.g., 2,2'-bipiperidine, Bip), unexpectedly stable duplexes having two platinated strands (even a unique G3,G4/G4,G5 heteroduplex) were formed. After enzymatic digestion of BipPt-G3 duplexes, the conformation of the relatively nondynamic G,G units was shown to be head-to-head (HH) by HPLC/mass spectrometric characterization. Because the HH conformation dominates at the G,G lesion in duplex DNA and in the BipPt-G3 duplexes, the stabilization of the duplex form only when the L nitrogen adducts possess bulk suggests that H-bonding interactions of the Pt-NH groups with the flanking DNA lead to local melting and to destabilization of oligomer duplexes. The marked dependence of adduct properties on L bulk and the minimal dependence on L chirality underscore the need for future exploration of the roles of the L periphery in affecting anticancer activity.
authors.affiliation: Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Beljanski
authors.forename: Julie M
authors.initials: JM
authors.lastname: Villanueva
authors.forename: Paul W
authors.initials: PW
authors.lastname: Doetsch
authors.forename: Giovanni
authors.initials: G
authors.lastname: Natile
authors.forename: Luigi G
authors.initials: LG
authors.lastname: Marzilli
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry*; D002945:Cisplatin / Q000737:chemistry*; D018736:DNA Adducts / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000737:chemistry; D004586:Electrophoresis; D006147:Guanine / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010984:Platinum / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000970:Antineoplastic Agents; D018736:DNA Adducts; D004277:DNA, Single-Stranded; D008024:Ligands; D009838:Oligodeoxyribonucleotides; C057270:cisplatin-DNA adduct; D010984:Platinum; D006147:Guanine; D002945:Cisplatin