The wide use of antifungal agents has led to the development of resistance in the pathogenic yeast strain Candida albicans. Gain-of-function mutations in transcription factors such as Tac1p demonstrated their ability to control expression of the ABC transporter genes CDR1 and CDR2, and mediation of azole resistance. Previously, we obtained a series of azole-resistant isolates with high-level expression of CDR1 or/and CDR2, and identified the novel H741D mutation in Tac1p. In the present study, the TAC1 alleles from isolate C13 were introduced into tac1Δ/Δ mutant. The H741D change was seen in TAC1C13 in addition to several other amino acid differences. Hyperactive alleles TAC1C13 exhibited higher minimum inhibitory concentrations (MICs) of fluconazole and itraconazole than that observed in SN152 containing the wild-type TAC1 allele. And alleles TAC1C13 conferred constitutively high levels of Cdr1p and Cdr2p. Moreover, the importance of H741D in conferring hyperactivity to TAC1 was also confirmed by site-directed mutagenesis. Compared with SN152, the presence of H741D resulted in > 2-fold increase in CDR1 and CDR2 gene and protein expression, > 4-fold increase in fluconazole and itraconazole MICs and higher rates of Rhodamine 6G efflux by 43.24%.

中文翻译：

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Tac1p 中的 H741D 突变有助于上调白色念珠菌中的 CDR1 和 CDR2 表达

抗真菌剂的广泛使用导致致病性酵母菌株白色念珠菌产生耐药性。Tac1p 等转录因子的功能获得性突变表明它们能够控制 ABC 转运蛋白基因 CDR1 和 CDR2 的表达，以及介导唑类抗性。此前，我们获得了一系列高水平表达CDR1或/和CDR2的唑类耐药菌株，并在Tac1p中鉴定了新的H741D突变。在本研究中，来自分离株 C13 的 TAC1 等位基因被引入 tac1Δ/Δ 突变体。除了几个其他氨基酸差异外，在 TAC1C13 中还观察到了 H741D 变化。与在含有野生型 TAC1 等位基因的 SN152 中观察到的相比，过度活跃的等位基因 TAC1C13 表现出更高的氟康唑和伊曲康唑的最小抑制浓度 (MIC)。并且等位基因 TAC1C13 赋予 Cdr1p 和 Cdr2p 组成性高水平。此外，H741D 在赋予 TAC1 过度活跃中的重要性也通过定点诱变得到证实。与 SN152 相比，H741D 的存在导致 CDR1 和 CDR2 基因和蛋白质表达增加 > 2 倍，氟康唑和伊曲康唑 MIC 增加 > 4 倍，罗丹明 6G 外排率提高 43.24%。