Azole drugs are the most frequently used antifungal agents. The pathogenic yeast Candida glabrata acquires resistance to azole drugs via single amino acid substitution mutations eliciting a gain-of-function (GOF) hyperactive phenotype in the Pdr1 transcription factor. These GOF mutants constitutively drive high transcription of target genes such as the ATP-binding cassette transporter-encoding CDR1 locus. Previous characterization of Pdr1 has demonstrated that this factor is negatively controlled by the action of a central regulatory domain (CRD) of ~700 amino acids, in which GOF mutations are often found. Our earlier experiments demonstrated that a Pdr1 derivative in which the CRD was deleted gave rise to a transcriptional regulator that could not be maintained as the sole copy of PDR1 in the cell owing to its toxically high activity. Using a set of GOF PDR1 alleles from azole-resistant clinical isolates, we have analyzed the mechanisms acting to repress Pdr1 transcriptional activity. Our data support the view that Pdr1-dependent transactivation is mediated by a complex network of transcriptional coactivators interacting with the extreme C-terminal part of Pdr1. These coactivators include but are not limited to the Mediator component Med15A. Activity of this C-terminal domain is controlled by the CRD and requires multiple regions across the C-terminus for normal function. We also provide genetic evidence for an element within the transactivation domain that mediates the interaction of Pdr1 with coactivators on one hand while restricting Pdr1 activity on the other hand. These data indicate that GOF mutations in PDR1 block nonidentical negative inputs that would otherwise restrain Pdr1 transcriptional activation. The strong C-terminal transactivation domain of Pdr1 uses multiple different protein regions to recruit coactivators.

唑类药物是最常用的抗真菌剂。致病性酵母光滑念珠菌通过在Pdr1转录因子中引起功能增强（GOF）超活性表型的单个氨基酸取代突变获得对唑类药物的抗性。这些GOF突变体组成性地驱动目标基因（如ATP结合盒转运体编码CDR1位点）的高转录。Pdr1的先前特征表明，该因子受〜700个氨基酸的中央调节域（CRD）的作用负控制，其中经常发现GOF突变。我们较早的实验表明，删除了CRD的Pdr1衍生物产生了一个转录调控因子，该转录调控因子不能作为CD的唯一拷贝而被维持。细胞中的PDR1具有高毒活性。使用一组GOF PDR1等位基因从耐唑的临床分离株，我们已经分析了抑制Pdr1转录活性的机制。我们的数据支持以下观点，即Pdr1依赖性反式激活是由与Pdr1的C末端极端部分相互作用的转录共激活因子的复杂网络介导的。这些共激活剂包括但不限于介体组分Med15A。此C末端域的活性受CRD控制，并且需要C末端的多个区域才能正常运行。我们还提供了反式激活域内一方面介导Pdr1与共激活因子相互作用而另一方面限制Pdr1活性的元素的遗传证据。这些数据表明PDR1中的GOF突变阻止不同的负输入，否则它们会限制Pdr1转录激活。Pdr1的强C末端反式激活结构域使用多个不同的蛋白质区域来募集共激活剂。