MULTIPLE PDR1P PDR3P BINDING-SITES ARE ESSENTIAL FOR NORMAL EXPRESSION OF THE ATP BINDING CASSETTE TRANSPORTER PROTEIN-ENCODING GENE PDR5/

Saccharomyces cerevisiae has large number of genes that can be genetic ally altered to produce a multiple or pleiotropic drug resistance phen otype. The homologous zinc finger transcription factors Pdr1p and Pdr3 p both elevate resistance to many drugs, including cycloheximide, This elevation in cycloheximide tolerance only occurs in the presence of a n intact copy of the PDR5 gene that encodes a plasma membrane-localize d ATP binding cassette transporter protein. Previously, we have found that a single binding site for Pdr3p present in the PDR5 promoter is s ufficient to provide Pdr3p-responsive gene expression. In this study, we have found that there are three sites in the PDR5 5'-noncoding regi on that are closely related to one another and are bound by both Pdr1p and Pdr3p, These elements have been designated Pdr1p/Pdr3p response e lements (PDREs), and their role in the maintenance of normal PDR5 expr ession has been analyzed, Mutations have been constructed in each PDRE and shown to eliminate Pdr1p/Pdr3p binding in vitro. Analysis of the effect of these mutant PDREs on normal PDR5 promoter function indicate s that each element is required for wild-type expression and drug resi stance. A single PDRE placed upstream of a yeast gene lacking its norm al upstream activation sequence is sufficient to confer Pdr1p responsi veness to this heterologous promoter.