The zinc cluster transcription factor Znc1 regulates Rta3-dependent miltefosine resistance in .

UNLABELLED

Zinc cluster transcription factors (ZCFs) are a family of transcription regulators that are almost exclusively found in the fungal kingdom. Activating mutations in the ZCFs Mrr1, Tac1, and Upc2 frequently cause acquired resistance to the widely used antifungal drug fluconazole in the pathogenic yeast . Similar to a hyperactive Tac1, a constitutively active form of the ZCF Znc1 causes increased fluconazole resistance by upregulating the multidrug efflux pump-encoding gene . Hyperactive forms of both Tac1 and Znc1 also cause overexpression of , which encodes a seven-transmembrane receptor protein involved in the regulation of asymmetric lipid distribution in the plasma membrane. expression is also upregulated by miltefosine, an antiparasitic drug that is active against fungal pathogens and considered for treatment of invasive candidiasis, and Δ mutants are hypersensitive to miltefosine. We found that activated forms of both Tac1 and Znc1 confer increased miltefosine resistance, which was dependent on whereas was dispensable. Intriguingly, the induction of expression by miltefosine depended on Znc1, but not Tac1, in contrast to the known Tac1-dependent upregulation by fluphenazine. In line with this observation, Δ mutants were hypersensitive to miltefosine, whereas Δ mutants showed wild-type tolerance. Forced expression of reverted the hypersensitivity of Δ mutants, demonstrating that the hypersensitivity was caused by the inability of the mutants to upregulate in response to the drug. These findings establish Znc1 as a key regulator of miltefosine-induced expression that is important for wild-type miltefosine tolerance.

IMPORTANCE

Transcription factors are central regulators of gene expression, and knowledge about which transcription factor regulates specific genes in response to a certain signal is important to understand the behavior of organisms. In the pathogenic yeast , the gene is required for wild-type tolerance of miltefosine, an antiparasitic drug that is considered for treatment of invasive candidiasis. Activated forms of the transcription factors Tac1 and Znc1 cause constitutive overexpression of and thereby increased miltefosine resistance, but only Tac1 mediates upregulation of in response to the known inducer fluphenazine. expression is also induced by miltefosine, and we found that this response depends on Znc1, whereas Tac1 is dispensable. Consequently, Δ mutants were hypersensitive to miltefosine, whereas Δ mutants showed wild-type tolerance. These findings demonstrate that Znc1 is the key regulator of expression in response to miltefosine that is important for wild-type miltefosine tolerance.