title: A mutation in yeast topoisomerase II that confers hypersensitivity to multiple classes of topoisomerase II poisons.
abstract: A mutation was constructed in the CAP homology domain of yeast topoisomerase II that resulted in hypersensitivity to the intercalating agent N-[4-(9-acridinylamino)-3-methoxy-phenyl]methanesulfonamide and the fluoroquinolone 6, 8-difluoro-7-(4'-hydroxyphenyl)-1-cyclopropyl-4-quinolone-3-carboxyli c acid, but not to etoposide. This mutation, which changes threonine at position 744 to proline, also confers hypersensitivity to anti-bacterial fluoroquinolones. The purified T744P mutant protein had wild type enzymatic activity in the absence of drugs, and no alteration in drug-independent DNA cleavage. Enhanced DNA cleavage in the presence of N-[4-(9-acridinylamino)-3-methoxy-phenyl]methanesulfonamide and fluoroquinolones was observed, in agreement with the results observed in vivo. DNA cleavage was also seen in the presence of norfloxacin and oxolinic acid, two quinolones that are inactive against eukaryotic topoisomerase II. The hypersensitivity was not associated with heat-stable covalent complexes, as was seen in another drug-hypersensitive mutant. Molecular modeling suggests that the mutation in the CAP homology domain may displace amino acids that play important roles in catalysis by topoisomerase II and may explain the drug-hypersensitive phenotype.
authors.affiliation: Molecular Pharmacology Department, St. Jude Children's Research Hospital, Memphis, Tennessee 38018, USA.
authors.forename: J
authors.initials: J
authors.lastname: Dong
authors.forename: J
authors.initials: J
authors.lastname: Walker
authors.forename: J L
authors.initials: JL
authors.lastname: Nitiss
mesh_terms: D000677:Amsacrine / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology; D001665:Binding Sites; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000145:classification / Q000494:pharmacology; D005057:Eukaryotic Cells; D024841:Fluoroquinolones; D007364:Intercalating Agents / Q000494:pharmacology; D008958:Models, Molecular; D009154:Mutation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae; D059005:Topoisomerase II Inhibitors
chemical_list: D000890:Anti-Infective Agents; D004791:Enzyme Inhibitors; D024841:Fluoroquinolones; D007364:Intercalating Agents; D059005:Topoisomerase II Inhibitors; D000677:Amsacrine; C070116:CP 115953; D004250:DNA Topoisomerases, Type II