Institut für Molekulare Infektionsbiologie, Universität Würzburg, Josef-Schneider-Str. 2, Bau D15, D-97080 Würzburg, Germany.
Antimicrob Agents Chemother. 2011 May;55(5):2212-23. doi: 10.1128/AAC.01343-10. Epub 2011 Mar 14.
Constitutive overexpression of the Mdr1 efflux pump is an important mechanism of acquired drug resistance in the yeast Candida albicans. The zinc cluster transcription factor Mrr1 is a central regulator of MDR1 expression, but other transcription factors have also been implicated in MDR1 regulation. To better understand how MDR1-mediated drug resistance is achieved in this fungal pathogen, we studied the interdependence of Mrr1 and two other MDR1 regulators, Upc2 and Cap1, in the control of MDR1 expression. A mutated, constitutively active Mrr1 could upregulate MDR1 and confer drug resistance in the absence of Upc2 or Cap1. On the other hand, Upc2 containing a gain-of-function mutation only slightly activated the MDR1 promoter, and this activation depended on the presence of a functional MRR1 gene. In contrast, a C-terminally truncated, activated form of Cap1 could upregulate MDR1 in a partially Mrr1-independent fashion. The induction of MDR1 expression by toxic chemicals occurred independently of Upc2 but required the presence of Mrr1 and also partially depended on Cap1. Transcriptional profiling and in vivo DNA binding studies showed that a constitutively active Mrr1 binds to and upregulates most of its direct target genes in the presence or absence of Cap1. Therefore, Mrr1 and Cap1 cooperate in the environmental induction of MDR1 expression in wild-type C. albicans, but gain-of-function mutations in either of the two transcription factors can independently mediate efflux pump overexpression and drug resistance.
组成型过表达 Mdr1 外排泵是酵母白色念珠菌获得性药物耐药的重要机制。锌簇转录因子 Mrr1 是 MDR1 表达的中央调节剂，但其他转录因子也与 MDR1 调节有关。为了更好地理解这种真菌病原体如何实现 MDR1 介导的耐药性，我们研究了 Mrr1 与另外两个 MDR1 调节剂 Upc2 和 Cap1 在 MDR1 表达调控中的相互依赖关系。突变的、组成型激活的 Mrr1 可以在没有 Upc2 或 Cap1 的情况下上调 MDR1 并赋予耐药性。另一方面，含有功能获得性突变的 Upc2 仅略微激活 MDR1 启动子，这种激活依赖于功能性 MRR1 基因的存在。相比之下，C 端截断的、激活形式的 Cap1 可以以部分不依赖 Mrr1 的方式上调 MDR1。有毒化学物质诱导 MDR1 表达独立于 Upc2 发生，但需要 Mrr1 的存在，也部分依赖于 Cap1。转录谱分析和体内 DNA 结合研究表明，组成型激活的 Mrr1 在存在或不存在 Cap1 的情况下结合并上调其大部分直接靶基因。因此，Mrr1 和 Cap1 在野生型 C. albicans 中共同参与 MDR1 表达的环境诱导，但这两个转录因子中的任何一个的功能获得性突变都可以独立介导外排泵过表达和耐药性。
