An A643T Mutation in the Transcription Factor Upc2p Causes Constitutive ERG11 Upregulation and Increased Fluconazole Resistance in Candida albicans
Open Access
- 1 January 2010
- journal article
- research article
- Published by American Society for Microbiology in Antimicrobial Agents and Chemotherapy
- Vol. 54 (1), 353-359
- https://doi.org/10.1128/aac.01102-09
Abstract
The zinc cluster transcription factor Upc2p mediates upregulation of ergosterol biosynthesis genes in response to ergosterol depletion in the fungal pathogen Candida albicans. One mechanism of acquired resistance to the antifungal drug fluconazole, which inhibits ergosterol biosynthesis, is constitutively increased expression of the ERG11 gene encoding the drug target enzyme. A G648D mutation in Upc2p has recently been shown to cause hyperactivity of the transcription factor, resulting in overexpression of ergosterol biosynthesis genes and increased fluconazole resistance. In order to investigate if gain-of-function mutations in Upc2p are a common mechanism of ERG11 upregulation and fluconazole resistance, we sequenced the UPC2 alleles of four ERG11-overexpressing, fluconazole-resistant C. albicans isolates and matched susceptible isolates from the same patients. In three of the isolate pairs, no differences in the UPC2 alleles were found, suggesting that mechanisms other than Upc2p mutations can cause ERG11 overexpression. One resistant isolate had become homozygous for a UPC2 allele containing a G1927A substitution that caused an alanine-to-threonine exchange at amino acid position 643 of Upc2p. Replacement of one of the endogenous UPC2 alleles in a fluconazole-susceptible strain by the UPC2A643T allele resulted in ERG11 overexpression and increased fluconazole resistance, which was further elevated when the A643T mutation was also introduced into the second UPC2 allele. These results further establish gain-of-function mutations in UPC2, which can be followed by loss of heterozygosity for the mutated allele, as a mechanism of ERG11 overexpression and increased fluconazole resistance in C. albicans, but other mechanisms of ERG11 upregulation also exist.Keywords
This publication has 25 references indexed in Scilit:
- Candida albicans UPC2 is transcriptionally induced in response to antifungal drugs and anaerobicity through Upc2p-dependent and -independent mechanismsMicrobiology, 2008
- Mutations in the multi‐drug resistance regulator MRR1, followed by loss of heterozygosity, are the main cause of MDR1 overexpression in fluconazole‐resistant Candida albicans strainsMolecular Microbiology, 2008
- A Gain-of-Function Mutation in the Transcription Factor Upc2p Causes Upregulation of Ergosterol Biosynthesis Genes and Increased Fluconazole Resistance in a Clinical Candida albicans IsolateEukaryotic Cell, 2008
- Environmental Induction of White–Opaque Switching in Candida albicansPLoS Pathogens, 2008
- Genomewide Location Analysis of Candida albicans Upc2p, a Regulator of Sterol Metabolism and Azole Drug ResistanceEukaryotic Cell, 2008
- An isochromosome confers drug resistance in vivo by amplification of two genes, ERG11 and TAC1Molecular Microbiology, 2008
- cis -Acting Elements within the Candida albicans ERG11 Promoter Mediate the Azole Response through Transcription Factor Upc2pEukaryotic Cell, 2007
- The Transcription Factor Mrr1p Controls Expression of the MDR1 Efflux Pump and Mediates Multidrug Resistance in Candida albicansPLoS Pathogens, 2007
- Genotypic Evolution of Azole Resistance Mechanisms in Sequential Candida albicans IsolatesEukaryotic Cell, 2007
- A family of oligopeptide transporters is required for growth of Candida albicans on proteinsMolecular Microbiology, 2006