title: Superhelical torsion controls DNA interstrand cross-linking by antitumor cis- diamminedichloroplatinum(II).
abstract: Negatively supercoiled, relaxed and linearized forms of pSP73 DNA were modified in cell-free medium by cis-diamminedichloroplatinum(II) (cisplatin). The frequency of interstrand cross-links (ICLs) formed in these DNAs has been determined by: (i) immunochemical analysis; (ii) an assay employing NaCN as a probe of DNA ICLs of cisplatin; (iii) gel electrophoresis under denaturing conditions. At low levels of the modification of DNA (<1 Pt atom fixed per 500 bp) the number of ICLs formed by cisplatin was radically enhanced in supercoiled in comparison with linearized or relaxed DNA. At these low levels of modification, the frequency of ICLs in supercoiled DNA was enhanced with increasing level of negative supercoiling or with decreasing level of modification. In addition, the replication mapping of DNA ICLs of cisplatin was consistent with these lesions being preferentially formed in negatively supercoiled DNA between guanine residues in both the 5'-d(GC)-3' and the 5'-d(CG)-3' sites. Among the DNA adducts of cisplatin the ICL has the markedly greatest capability to unwind the double helix. We suggest that the formation of ICLs of cisplatin is thermodynamically more favored in negatively supercoiled DNA owing mainly to the relaxation of supercoils.
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno.
authors.forename: O
authors.initials: O
authors.lastname: Vrána
authors.forename: V
authors.initials: V
authors.lastname: Boudný
authors.forename: V
authors.initials: V
authors.lastname: Brabec
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D001667:Binding, Competitive; D002945:Cisplatin / Q000494:pharmacology*; D003432:Cross-Linking Reagents / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism; D004270:DNA, Circular / Q000378:metabolism; D004278:DNA, Superhelical / Q000187:drug effects*; D004587:Electrophoresis, Agar Gel; D004797:Enzyme-Linked Immunosorbent Assay; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D010957:Plasmids / Q000187:drug effects / Q000378:metabolism; D015183:Restriction Mapping; D012966:Sodium Cyanide / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D018736:DNA Adducts; D004270:DNA, Circular; D004278:DNA, Superhelical; D012966:Sodium Cyanide; D002945:Cisplatin