title: Atomic force microscopy examination of conformations of polynucleotides in response to platinum isomers: significance of GC content at broken ends.
abstract: Atomic force microscopy is a technique that enables visualization of macromolecular conformations of polynucleotides at nanometer resolution. We investigated the results of interactions of cisplatin, a DNA binding anticancer drug, and its inactive counterpart, transplatin isomer, on the molecular conformation of polynucleotides: poly d(G-C). poly d(G-C) (polyGC) and poly d(A-T). poly d(A-T) (polyAT). We observed that polyAT exhibited an increased number of enlarged ends of molecules, which we attribute to unwound and/or collapsed regions of polyAT. PolyGC molecules did not show such ends unless cisplatin was added to the PolyGC polymers. Transplatin had the apparent effect of causing overlapping or stacking of the polymer molecules. Addition of exonuclease-III to these polymers removed the visible enlarged ends. The effects of cisplatin as compared to transplatin on the polyGC duplex polymers provide support for the presence of intrastrand covalent linkages, consistent with known N7 guanine interaction of the cis isomer on molecular conformation. Furthermore, our results indicate that the mechanism of interactions of DNA with cisplatin may be dependent on the GC content of the molecules. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 68-72, 2000.
authors.affiliation: Department of Radiation Medicine, Georgetown University Medical Center, Washington, District of Columbia, USA.
authors.forename: D
authors.initials: D
authors.lastname: Pang
authors.forename: S
authors.initials: S
authors.lastname: Chasovskikh
authors.forename: J S
authors.initials: JS
authors.lastname: Cohen
authors.forename: C
authors.initials: C
authors.lastname: Obcemea
authors.forename: A
authors.initials: A
authors.lastname: Dritschilo
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001482:Base Composition; D020029:Base Pairing; D002945:Cisplatin / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism; D018625:Microscopy, Atomic Force; D009690:Nucleic Acid Conformation; D011119:Polynucleotides / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D011119:Polynucleotides; C034697:transplatin; D004247:DNA; D002945:Cisplatin