A yeast type II topoisomerase selected for resistance to quinolones. Mutation of histidine 1012 to tyrosine confers resistance to nonintercalative drugs but hypersensitivity to ellipticine

J Biol Chem. 1995 Jan 27;270(4):1913-20. doi: 10.1074/jbc.270.4.1913.


A mutant yeast type II topoisomerase was generated by in vitro mutagenesis followed by selection in vivo for resistance to the quinolone CP-115,953. The resulting mutant enzyme had a single point mutation which converted His1012 to Tyr (top2H1012Y). top2H1012Y was overexpressed in yeast, purified, and characterized in vitro. The mutant type II topoisomerase was slightly less active than the wild type enzyme, apparently due to a decreased affinity for DNA. The affinity of the mutant enzyme for ATP was similar to that of wild type topoisomerase II. As determined by DNA cleavage assays, top2H1012Y was resistant to CP-115,953 and etoposide both prior to and following the DNA strand-passage event. In marked contrast, the mutant enzyme displayed wild type sensitivity to amsacrine and was severalfold hypersensitive to ellipticine. A similar pattern of resistance was observed in yeast cells harboring the top2H1012Y allele. Thus, it appears that the mutant type II topoisomerase can distinguish between nonintercalative and intercalative agents. Finally, the His1012-->Tyr mutation defines a potential new drug resistance-conferring region on eukaryotic topoisomerase II.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Anti-Infective Agents / pharmacology*
  • DNA Topoisomerases, Type II / chemistry
  • DNA Topoisomerases, Type II / metabolism*
  • Drug Resistance
  • Ellipticines / pharmacology*
  • Fluoroquinolones*
  • Histidine*
  • Humans
  • Kinetics
  • Mice
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Point Mutation*
  • Quinolones / pharmacology*
  • Recombinant Proteins / antagonists & inhibitors
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / enzymology*
  • Sequence Homology, Amino Acid
  • Topoisomerase II Inhibitors
  • Tyrosine*


  • Anti-Infective Agents
  • Ellipticines
  • Fluoroquinolones
  • Quinolones
  • Recombinant Proteins
  • Topoisomerase II Inhibitors
  • ellipticine
  • CP 115953
  • Tyrosine
  • Histidine
  • DNA Topoisomerases, Type II