Role of the transcription factors Tac1a and Tac1b in azole resistance in Candida auris

Candida auris (Candidozyma auris) is a yeast pathogen that poses a public health threat because of its ability to develop antifungal resistance. Notably, most C. auris isolates are resistant to fluconazole. The efflux pump Cdr1 is a key contributor of azole resistance in C. auris. In C. albicans, Cdr1 is regulated by the transcription factor Tac1, which has two orthologs in C. auris (Tac1a and Tac1b). While the role of Tac1b has been described, little is known about Tac1a. In this study, we characterized the respective roles of Tac1a and Tac1b in azole resistance. To investigate their transcriptional regulation and binding targets, we performed RNA sequencing and ChEC-seq (Chromatin endogenous cleavage sequencing) for both transcription factors. RNA sequencing was carried out by comparing hyperactivated mutants (TAC1a-HA or TAC1b-HA) with the wild-type strain IV.1. ChEC-seq was performed in strains carrying endogenous C-terminal MNase fusions (TAC1a-MNase and TAC1b-MNase) and in a control strain expressing ectopically MNase (Free MNase). Both Tac1a and Tac1b mediate azole resistance in C. auris via regulation of Cdr1, with overlapping downstream targets and evidence of autoregulation. We used ChEC-seq (Chromatin endogenous cleavage sequencing) analysis to map the genomic occupancy of two zinc-finger transcription factor transcriptions, Tac1a and Tac1b, in the opportunistic yeast Candida auris. DNA- binding was determined by comparing DNA sequence counts in strains where Tac1a and Tac1b were MNase-tagged (Tac1a-Mnase and Tac1b-MNase) at their C-terminal regions to that of a control strain ectopically expressing MNase.