Repression of pleiotrophic drug resistance genes in Saccharomyces cerevisiae using chimeric transcriptional repressors

Yeast is a powerful model system for studying the action of small molecule therapeutics. An important limitation has been low efficacy of many small molecules in yeast due to limited intracellular drug accumulation. We used the DNA binding domain of the pleiotropic drug resistance regulator Pdr1 fused in-frame to transcription repressors to repress Pdr1 regulated genes. Expression of these regulators conferred dominant enhancement of drug sensitivity and led to greatly diminished levels of Pdr1p regulated transcripts, including the yeast p-glycoprotein homologue Pdr5. Enhanced sensitivity was seen for a wide range of small molecules. Biochemical measurements demonstrated enhanced accumulation of rhodamine in yeast cells carrying the chimeras. These repressors of Pdr1p regulated transcripts can be introduced into large collections of strains such as the S. cerevisiae deletion set, and enhance the utility of yeast for studying drug action and for mechanism-based drug discovery. Keywords: Comparison of genetic variants We determined the profiles of gene expression in yeast strains expressing dominant-negative Pdr1-fusion transcription factors. Yeast strains expressing different Pdr1-fusion repressors were analyzed by extracting total RNA and hybridization to Affymetrix GeneChip YG-s98 microarrays