Yeast Tools for Studying Type II Topoisomerases in Budding Yeast

DNA topoisomerases perform diverse functions in DNA metabolism. Type II topoisomerases, which carry out their reaction through a double-strand break intermediate, are absolutely required to separate replicated chromosomes prior to mitosis and play key roles in replication, transcription, and chromosome stability. The yeast Saccharomyces cerevisiae has been a premier system for exploring the biological roles of topoisomerases, and since type II enzymes are required for viability, the availability of conditional mutants greatly enhances the ability to dissect their biological roles. This chapter provides a critical discussion of yeast top2 mutants and plasmids for expressing and genetically manipulating the gene encoding the enzyme. An additional advantage of the yeast is the ability to functionally express human Top2α and Top2β in yeast to determine whether the human enzymes have unique characteristics that impact their biological functions. Therefore, this chapter also discusses plasmids that are available to express human Top2 enzymes in yeast. Finally, yeast has been particularly valuable in studying anti-cancer drugs that target Top2. This chapter discusses novel and powerful approaches for enhancing drug accumulation, allowing detailed examination of various topoisomerase inhibitors and poisons.