In vivo characterization of the drug resistance profile of the major ABC transporters and other components of the yeast pleiotropic drug resistance network.

Multidrug resistance (MDR) mediated by broad specificity transporters is one of the most important strategies used by pathogens, including cancer cells, to evade chemotherapy. In the yeast Saccharomyces cerevisiae, a complex pleiotropic drug resistance (PDR) network of genes involved in MDR is composed of the transcriptional regulators Pdr1p and Pdr3p, which activate expression of the ATP-binding cassette (ABC) MDR transporters-encoding genes PDR5, SNQ2, and YOR1 as well as other not yet identified genes. We have screened 349 toxic compounds in isogenic S.