Novel target genes of the yeast regulator Pdr1p: a contribution of the TPO1 gene in resistance to quinidine and other drugs

The yeast transcription factor Pdr1p regulates the expression of a number o f genes, several of which encode ATP-driven transport proteins involved in multiple drug resistance. Among 20 genes containing binding consensus seque nces for the transcription factor Pdr1p in their promoter. we studied more particularly the regulation and function of PDR16 (involved in phospholipid synthesis), TPO1 (involved in vacuolar transport of polyamines), YAL061W ( homologous to polyol dehydrogenases) and YLR346C (unknown function). We fou nd that the regulation of these four genes depends on Pdr1p, since promoter activities studied by lacZ fusion analysis and mRNA levels studied by Nort hern blotting analysis changed upon deletion or hyperactivation by the pdr1 -3 mutant of this transcription factor, The drug sensitivity of the strains deleted for these genes revealed that TPO1, a gene previously found to be involved in spermidine resistance and vacuolar polyamine transport, is a de terminant of multidrug transporter since it also mediates growth resistance to cycloheximide and quinidine. This resistance pattern overlapped with th at of YOR273C, a homolog of TPO1. These two homologous transporters are thu s bonafide members of the phylogenetic subfamily DHA1 (drug/proton antiport TC 2.A.1. 2) of the major facilitator superfamily. Both YOR273C and TPO1 a s well as at least one other determinant involved in the yeast pleiotropic drug resistance network contribute to resistance to a quinoline-containing antimalarial drug. (C) 2001 Elsevier Science B.V. All rights reserved.