title: Mammalian topoisomerase II activity is modulated by the DNA minor groove binder distamycin in simian virus 40 DNA.
abstract: DNA topoisomerases II are nuclear enzymes that have been identified recently as targets for some of the most active anticancer drugs. Antitumor topoisomerase II inhibitors such as teniposide (VM-26) produce enzyme-induced DNA cleavage and inhibition of enzyme activity. By adding to such reactions distamycin, a compound whose effects on DNA have been extensively characterized, we investigated the effects of drug binding upon topoisomerase II-mediated DNA cleavage induced by VM-26. We have found a correspondence between distamycin binding (determined by footprinting analysis) and topoisomerase II-mediated cleavage of SV40 DNA (determined by sequencing gel analysis). Distamycin binding potentiated the cleavage of specific sites in the near proximity of distamycin-binding sites (within at least 25 base pairs), which indicates that DNA secondary structure is involved in topoisomerase II-DNA interactions. That distamycin potentiated cleavage only at sites that were recognized in the absence of distamycin and suppressed cleavage directly at distamycin-binding sites indicates that topoisomerase II recognizes DNA on the basis of primary sequence. In addition, distamycin stimulated topoisomerase II-mediated DNA relaxation and antagonized the inhibitory effect of VM-26. These results show that the DNA sequence-specific binding of distamycin produces local and propagated effects in the DNA which markedly affect topoisomerase II activity.
authors.affiliation: Laboratory of Molecular Pharmacology, National Cancer Institute, Bethesda, Maryland 20892.
authors.forename: M
authors.initials: M
authors.lastname: Fesen
authors.forename: Y
authors.initials: Y
authors.lastname: Pommier
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004262:DNA Restriction Enzymes; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism*; D004214:Distamycins / Q000378:metabolism / Q000494:pharmacology*; D004347:Drug Interactions; D004586:Electrophoresis; D007939:Leukemia L1210 / Q000201:enzymology; D051379:Mice; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation / Q000187:drug effects; D011758:Pyrroles / Q000494:pharmacology*; D012091:Repetitive Sequences, Nucleic Acid; D013539:Simian virus 40 / Q000235:genetics*; D013713:Teniposide / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D004279:DNA, Viral; D004214:Distamycins; D011758:Pyrroles; D013713:Teniposide; D004262:DNA Restriction Enzymes; D004250:DNA Topoisomerases, Type II