Is Involved in the Suppression of Basal Transcription of ABC Transporters and Drug Resistance in the ρ Cells of .

In , the Rpd3L complex contains a histone deacetylase, Rpd3, and the DNA binding proteins, Ume6 and Ash1, and acts as a transcriptional repressor or activator. We previously showed that and are required for the activation of , which encodes a major efflux pump, and pleiotropic drug resistance (PDR) in ρ cells, which lack mitochondrial DNA. However, there are inconsistent reports regarding whether and are required for Pdr5-mediated PDR in ρ cells with mitochondrial DNA. Since expression or PDR in the ρ cells of the Δ and Δ mutants have primarily been examined using fermentable media, mixed cultures of ρ and ρ cells could be used. Therefore, we examined whether and are required for basal and drug-induced transcription and PDR in ρ cells using fermentable and nonfermentable media. suppresses the basal transcription levels of the ABC transporters, including , and drug resistance in ρ cells independent of the carbon source used in the growth medium. In contrast, is required for drug resistance but did not interfere with the basal mRNA levels. is also required for the cycloheximide-induced transcription of in nonfermentable media but not in fermentable media.