SCT1 mutants suppress the camptothecin sensitivity of yeast cells expressing wild-type DNA topoisomerase I

Academic Article


  • Camptothecin is a potent antineoplastic agent that interferes with the action of eukaryotic DNA topoisomerase I; the covalent enzyme-DNA intermediate is reversibly stabilized, leading to G2 arrest and cell death. We used a genetic screen to identify cellular factors, other than DNA topoisomerase I, that participate in the process of camptothecin-induced cell death. Following ethyl methanesulfonate mutagenesis of top1Δ yeast cells expressing plasmidborne wild-type DNA topoisomerase I, six dominant suppressors of camptothecin toxicity were isolated that define a single genetic locus, sct1. Mutant SCT1 cells expressed DNA topoisomerase I protein of similar specific activity and camptothecin sensitivity to that of congenic, drug-sensitive sct1 cells, yet were resistant to camptothecin- mediated lethality. Moreover, camptothecin-treated SCT1 cells did not exhibit the G2-arrested, terminal phenotype characteristic of drug-treated wild- type cells. SCT1 cell sensitivity to other DNA-damaging agents suggests that alterations in SCT1 function suppress camptothecin-induced DNA damage produced in the presence of yeast DNA topoisomerase I.
  • Digital Object Identifier (doi)

    Author List

  • Kauh EA; Bjornsti MA
  • Start Page

  • 6299
  • End Page

  • 6303
  • Volume

  • 92
  • Issue

  • 14