Yeast cells expressing differential levels of human or yeast DNA topoisomerase II: a potent tool for identification and characterization of topoisomerase II-targeting antitumour agents
DNA topoisomerase II is the target of a variety of important antitumor agents, including etoposide, adriamycin, and amsacrine. We have constructed a system for analyzing the action of anti-topoisomerase II agents using the yeast Saccharomyces cerevisiae and have constructed vectors for expressing human topoisomerase II functionally in yeast. We have demonstrated that temperature-conditional yeast TOP2 mutants can be complemented by expression of wild-type human topoisomerase II alpha. Furthermore, expression of human topoisomerase II in yeast results in a quantitatively unique pattern of sensitivity to amsacrine. We also have constructed mutations in human TOP2 based on previously identified mutations from a human cell line selected for resistance to teniposide. Our experiments demonstrate that mutation of either arginine 450 or proline 803 of human topoisomerase II can result in an enzyme that has altered sensitivity to anti-topoisomerase II agents, and that a human enzyme carrying both mutations confers a higher level of drug resistance than enzymes carrying either single mutation.