text: Pdr1p is a main regulator of PDR genes and is known to target about 50 genes. Pdr1p binds to sequence 5-TCCGYGGR-3 of PDRE, which is located within the promoter sequences of its target genes. 218 genes are reported to possess PDRE. Pdr1p is observed to  bind PDRE sites on DNA at basal level and also after simulation with toxins. This shows that Pdr1p-DNA interaction isnt dependent on toxic stimulation. This also suggests an involvement of activator(s) or co-activator(s) that induce PDR genes along with Pdr1p. Pdr1p has a functional homolog called Pdr3p encoded by gene called PDR3'. Pdr3p is known to be regulated by Pdr3p and Pdr1p. Pdr1p can form a homodimer with itself or heterodimer with Pdr3p. 
  Loss of function studies of both PDR1 and PDR3 revealed that Pdr1p mutant shows lower tolerance (grows less in culture) against organic toxins such as cycloheximide and oligomycin. This confirms the functions of Prf1p that confer stronger drug response phenotype than Pdr3p. However, Pdr3p is crucial for PDR responses since cells containing loss of function mutation in both PDR1 and PDR3 genes weren't able to grow at all in the presence of those two toxins. 
  Both Pdr1p and Pdr3p regulate Pdr5p, which is an ATP-binding cassette transporter. A single amino acid substitution mutation, which is a gain of function mutation of Pdr1p denoted as pdr1-3 (F815S, substitution mutation of Phenylalanine at 815th of the polypeptide by Serine) leads to an over-expression of mRNA of PDR5, which codes for Pdr5p. For cells treated with fluphenazine, Pdr1p was the only transcription factor necessary for PDR response genes induction. But at basal level, Pdr1p can be partially compensated by Pdr3p, a functional homolog of Pdr1p.