title: DNA-DNA interstrand cross-linking by cis-diamminedichloroplatinum(II): N7(dG)-to-N7(dG) cross-linking at 5'-d(GC) in synthetic oligonucleotides.
abstract: The nucleotide sequence specificity of the DNA-DNA interstrand cross-linking reaction of cis-diamminedichloroplatinum(II) (cis-DDP) was studied in synthetic oligonucleotides. Of six self-complementary DNAs tested, only those containing the central sequence 5'-d(GC) formed appreciable interstrand cross-linked product, as assayed by denaturing polyacrylamide gel electrophoresis (DPAGE). The nucleotide connectivity of the interstrand cross-link was defined by sequence random oxidative fragmentation followed by DPAGE, revealing that dG residues on opposite strands at the sequence 5'-d(GC) were connected to one another. The covalent structure of the cross-link was established following hydrolysis of the phosphodiester backbone of a structurally homogeneous sample of a cis-DDP interstrand cross-linked DNA tetradecamer. HPLC analysis of the hydrolysate returned all of the deoxynucleoside residues from the starting DNA except for two deoxyguanosine residues. Also returned was diammine-bis-[N7-(2'- deoxyguanosyl)]platinum(II)2+, identified by a combination of spectroscopic methods, and comparison to a synthetic authentic sample. This study directly establishes that cis-DDP forms interstrand cross-links at the duplex sequence 5'-d(GC), linking deoxyguanosine residues on opposite strands at N7 through a bridging platinum atom. Computer simulation of the interstrand cross-linked product using molecular mechanics energy minimization and molecular dynamics revealed significant structural reorganization at the site of the cross-link including a ca 40 degrees angle between the platinated guaninyl residues, which propagated to adjacent residues by base stacking to yield duplexes bent by some 30 degrees toward the major groove.
authors.affiliation: Department of Chemistry, University of Washington, Seattle 98195, USA.
authors.forename: H
authors.initials: H
authors.lastname: Huang
authors.forename: J
authors.initials: J
authors.lastname: Woo
authors.forename: S C
authors.initials: SC
authors.lastname: Alley
authors.forename: P B
authors.initials: PB
authors.lastname: Hopkins
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry*; D001483:Base Sequence; D001665:Binding Sites; D002945:Cisplatin / Q000737:chemistry*; D003198:Computer Simulation; D003432:Cross-Linking Reagents / Q000737:chemistry; D003596:Cytosine / Q000737:chemistry; D004247:DNA / Q000138:chemical synthesis / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D006147:Guanine; D003596:Cytosine; D004247:DNA; D002945:Cisplatin