Genomewide Location Analysis of Candida albicans Upc2p, a Regulator of Sterol Metabolism and Azole Drug Resistance

Abstract

ABSTRACT Upc2p, a transcription factor of the zinc cluster family, is an important regulator of sterol biosynthesis and azole drug resistance in Candida albicans . To better understand Upc2p function in C. albicans , we used genomewide location profiling to identify the transcriptional targets of Upc2p in vivo. A triple hemagglutinin epitope, introduced at the C terminus of Upc2p, conferred a gain-of-function effect on the fusion protein. Location profiling identified 202 bound promoters ( P < 0.05). Overrepresented functional groups of genes whose promoters were bound by Upc2p included 12 genes involved in ergosterol biosynthesis ( NCP1 , ERG11 , ERG2 , and others), 18 genes encoding ribosomal subunits ( RPS30 , RPL32 , RPL12 , and others), 3 genes encoding drug transporters ( CDR1 , MDR1 , and YOR1 ), 4 genes encoding transcription factors ( INO2 , ACE2 , SUT1 , and UPC2 ), and 6 genes involved in sulfur amino acid metabolism ( MET6 , SAM2 , SAH1 , and others). Bioinformatic analyses suggested that Upc2p binds to the DNA motif 5′-VNCGBDTR that includes the previously characterized Upc2p binding site 5′-TCGTATA. Northern blot analysis showed that increased binding correlates with increased expression for the analyzed Upc2p targets ( ERG11 , MDR1 , CDR1 , YOR1 , SUT1 , SMF12 , and CBP1 ). The analysis of ERG11 , MDR1 , and CDR1 transcripts in wild-type and upc2 Δ/ upc2 Δ strains grown under Upc2p-activating conditions (lovastatin treatment and hypoxia) showed that Upc2p regulates its targets in a complex manner, acting as an activator or as a repressor depending upon the target and the activating condition. Taken together, our results indicate that Upc2p is a key regulator of ergosterol metabolism. They also suggest that Upc2p may contribute to azole resistance by regulating the expression of drug efflux pump-encoding genes in addition to ergosterol biosynthesis genes.