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Librais GMN, Jiang Y, Razzaq I, Brandl CJ, Shapiro RS, Lajoie P. Evolutionary diversity of the control of the azole response by Tra1 across yeast species. G3 (BETHESDA, MD.) 2024; 14:jkad250. [PMID: 37889998 PMCID: PMC10849324 DOI: 10.1093/g3journal/jkad250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 02/16/2023] [Accepted: 10/20/2023] [Indexed: 10/29/2023]
Abstract
Tra1 is an essential coactivator protein of the yeast SAGA and NuA4 acetyltransferase complexes that regulate gene expression through multiple mechanisms including the acetylation of histone proteins. Tra1 is a pseudokinase of the PIKK family characterized by a C-terminal PI3K domain with no known kinase activity. However, mutations of specific arginine residues to glutamine in the PI3K domains (an allele termed tra1Q3) result in reduced growth and increased sensitivity to multiple stresses. In the opportunistic fungal pathogen Candida albicans, the tra1Q3 allele reduces pathogenicity and increases sensitivity to the echinocandin antifungal drug caspofungin, which disrupts the fungal cell wall. Here, we found that compromised Tra1 function, in contrast to what is seen with caspofungin, increases tolerance to the azole class of antifungal drugs, which inhibits ergosterol synthesis. In C. albicans, tra1Q3 increases the expression of genes linked to azole resistance, such as ERG11 and CDR1. CDR1 encodes a multidrug ABC transporter associated with efflux of multiple xenobiotics, including azoles. Consequently, cells carrying tra1Q3 show reduced intracellular accumulation of fluconazole. In contrast, a tra1Q3 Saccharomyces cerevisiae strain displayed opposite phenotypes: decreased tolerance to azole, decreased expression of the efflux pump PDR5, and increased intracellular accumulation of fluconazole. Therefore, our data provide evidence that Tra1 differentially regulates the antifungal response across yeast species.
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Affiliation(s)
| | - Yuwei Jiang
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Iqra Razzaq
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Christopher J Brandl
- Department of Biochemistry, The University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Rebecca S Shapiro
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Patrick Lajoie
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, N6A 5C1, Canada
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Jordá T, Barba-Aliaga M, Rozès N, Alepuz P, Martínez-Pastor MT, Puig S. Transcriptional regulation of ergosterol biosynthesis genes in response to iron deficiency. Environ Microbiol 2022; 24:5248-5260. [PMID: 36382795 DOI: 10.1111/1462-2920.16157] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 08/01/2022] [Indexed: 01/07/2023]
Abstract
Iron participates as an essential cofactor in the biosynthesis of critical cellular components, including DNA, proteins and lipids. The ergosterol biosynthetic pathway, which is an important target of antifungal treatments, depends on iron in four enzymatic steps. Our results in the model yeast Saccharomyces cerevisiae show that the expression of ergosterol biosynthesis (ERG) genes is tightly modulated by iron availability probably through the iron-dependent variation of sterol and heme levels. Whereas the transcription factors Upc2 and Ecm22 are responsible for the activation of ERG genes upon iron deficiency, the heme-dependent factor Hap1 triggers their Tup1-mediated transcriptional repression. The combined regulation by both activating and repressing regulatory factors allows for the fine-tuning of ERG transcript levels along the progress of iron deficiency, avoiding the accumulation of toxic sterol intermediates and enabling efficient adaptation to rapidly changing conditions. The lack of these regulatory factors leads to changes in the yeast sterol profile upon iron-deficient conditions. Both environmental iron availability and specific regulatory factors should be considered in ergosterol antifungal treatments.
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Affiliation(s)
- Tania Jordá
- Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain
| | - Marina Barba-Aliaga
- Instituto de Biotecnología y Biomedicina (Biotecmed), Universitat de València, Burjassot, Valencia, Spain
- Departamento de Bioquímica y Biología Molecular, Universitat de València, Burjassot, Valencia, Spain
| | - Nicolas Rozès
- Departament de Bioquímica i Biotecnologia, Facultat d'Enologia, Universitat Rovira i Virgili, Tarragona, Spain
| | - Paula Alepuz
- Instituto de Biotecnología y Biomedicina (Biotecmed), Universitat de València, Burjassot, Valencia, Spain
- Departamento de Bioquímica y Biología Molecular, Universitat de València, Burjassot, Valencia, Spain
| | | | - Sergi Puig
- Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain
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Pérez G, Lopez-Moya F, Chuina E, Ibañez-Vea M, Garde E, López-Llorca LV, Pisabarro AG, Ramírez L. Strain Degeneration in Pleurotus ostreatus: A Genotype Dependent Oxidative Stress Process Which Triggers Oxidative Stress, Cellular Detoxifying and Cell Wall Reshaping Genes. J Fungi (Basel) 2021; 7:jof7100862. [PMID: 34682283 PMCID: PMC8537115 DOI: 10.3390/jof7100862] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/08/2021] [Accepted: 10/09/2021] [Indexed: 12/13/2022] Open
Abstract
Strain degeneration has been defined as a decrease or loss in the yield of important commercial traits resulting from subsequent culture, which ultimately leads to Reactive Oxygen Species (ROS) production. Pleurotus ostreatus is a lignin-producing nematophagous edible mushroom. Mycelia for mushroom production are usually maintained in subsequent culture in solid media and frequently show symptoms of strain degeneration. The dikaryotic strain P. ostreatus (DkN001) has been used in our lab as a model organism for different purposes. Hence, different tools have been developed to uncover genetic and molecular aspects of this fungus. In this work, strain degeneration was studied in a full-sib monokaryotic progeny of the DkN001 strain with fast (F) and slow (S) growth rates by using different experimental approaches (light microscopy, malondialdehyde levels, whole-genome transcriptome analysis, and chitosan effect on monokaryotic mycelia). The results obtained showed that: (i) strain degeneration in P. ostreatus is linked to oxidative stress, (ii) the oxidative stress response in monokaryons is genotype dependent, (iii) stress and detoxifying genes are highly expressed in S monokaryons with symptoms of strain degeneration, (iv) chitosan addition to F and S monokaryons uncovered the constitutive expression of both oxidative stress and cellular detoxifying genes in S monokaryon strains which suggest their adaptation to oxidative stress, and (v) the overexpression of the cell wall genes, Uap1 and Cda1, in S monokaryons with strain degeneration phenotype indicates cell wall reshaping and the activation of High Osmolarity Glycerol (HOG) and Cell Wall Integrity (CWI) pathways. These results could constitute a hallmark for mushroom producers to distinguish strain degeneration in commercial mushrooms.
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Affiliation(s)
- Gumer Pérez
- Genetics, Genomics and Microbiology Research Group, Institute for Multidisciplinary Research in Applied Biology (IMAB), Public University of Navarre (UPNA), 31006 Pamplona, Spain; (G.P.); (E.C.); (M.I.-V.); (E.G.); (A.G.P.)
| | - Federico Lopez-Moya
- Laboratory of Plant Pathology, Department of Marine Sciences and Applied Biology, University of Alicante, 03690 Alicante, Spain; (F.L.-M.); (L.V.L.-L.)
| | - Emilia Chuina
- Genetics, Genomics and Microbiology Research Group, Institute for Multidisciplinary Research in Applied Biology (IMAB), Public University of Navarre (UPNA), 31006 Pamplona, Spain; (G.P.); (E.C.); (M.I.-V.); (E.G.); (A.G.P.)
| | - María Ibañez-Vea
- Genetics, Genomics and Microbiology Research Group, Institute for Multidisciplinary Research in Applied Biology (IMAB), Public University of Navarre (UPNA), 31006 Pamplona, Spain; (G.P.); (E.C.); (M.I.-V.); (E.G.); (A.G.P.)
| | - Edurne Garde
- Genetics, Genomics and Microbiology Research Group, Institute for Multidisciplinary Research in Applied Biology (IMAB), Public University of Navarre (UPNA), 31006 Pamplona, Spain; (G.P.); (E.C.); (M.I.-V.); (E.G.); (A.G.P.)
| | - Luis V. López-Llorca
- Laboratory of Plant Pathology, Department of Marine Sciences and Applied Biology, University of Alicante, 03690 Alicante, Spain; (F.L.-M.); (L.V.L.-L.)
| | - Antonio G. Pisabarro
- Genetics, Genomics and Microbiology Research Group, Institute for Multidisciplinary Research in Applied Biology (IMAB), Public University of Navarre (UPNA), 31006 Pamplona, Spain; (G.P.); (E.C.); (M.I.-V.); (E.G.); (A.G.P.)
| | - Lucía Ramírez
- Genetics, Genomics and Microbiology Research Group, Institute for Multidisciplinary Research in Applied Biology (IMAB), Public University of Navarre (UPNA), 31006 Pamplona, Spain; (G.P.); (E.C.); (M.I.-V.); (E.G.); (A.G.P.)
- Correspondence:
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Razzaq I, Berg MD, Jiang Y, Genereaux J, Uthayakumar D, Kim GH, Agyare-Tabbi M, Halder V, Brandl CJ, Lajoie P, Shapiro RS. The SAGA and NuA4 component Tra1 regulates Candida albicans drug resistance and pathogenesis. Genetics 2021; 219:iyab131. [PMID: 34849885 PMCID: PMC8633099 DOI: 10.1093/genetics/iyab131] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/02/2021] [Indexed: 11/14/2022] Open
Abstract
Candida albicans is the most common cause of death from fungal infections. The emergence of resistant strains reducing the efficacy of first-line therapy with echinocandins, such as caspofungin calls for the identification of alternative therapeutic strategies. Tra1 is an essential component of the SAGA and NuA4 transcriptional co-activator complexes. As a PIKK family member, Tra1 is characterized by a C-terminal phosphoinositide 3-kinase domain. In Saccharomyces cerevisiae, the assembly and function of SAGA and NuA4 are compromised by a Tra1 variant (Tra1Q3) with three arginine residues in the putative ATP-binding cleft changed to glutamine. Whole transcriptome analysis of the S. cerevisiae tra1Q3 strain highlights Tra1's role in global transcription, stress response, and cell wall integrity. As a result, tra1Q3 increases susceptibility to multiple stressors, including caspofungin. Moreover, the same tra1Q3 allele in the pathogenic yeast C. albicans causes similar phenotypes, suggesting that Tra1 broadly mediates the antifungal response across yeast species. Transcriptional profiling in C. albicans identified 68 genes that were differentially expressed when the tra1Q3 strain was treated with caspofungin, as compared to gene expression changes induced by either tra1Q3 or caspofungin alone. Included in this set were genes involved in cell wall maintenance, adhesion, and filamentous growth. Indeed, the tra1Q3 allele reduces filamentation and other pathogenesis traits in C. albicans. Thus, Tra1 emerges as a promising therapeutic target for fungal infections.
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Affiliation(s)
- Iqra Razzaq
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G2W1, Canada
| | - Matthew D Berg
- Department of Biochemistry, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Yuwei Jiang
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Julie Genereaux
- Department of Biochemistry, The University of Western Ontario, London, ON N6A 5C1, Canada
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Deeva Uthayakumar
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G2W1, Canada
| | - Grace H Kim
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G2W1, Canada
| | - Michelle Agyare-Tabbi
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G2W1, Canada
| | - Viola Halder
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G2W1, Canada
| | - Christopher J Brandl
- Department of Biochemistry, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Patrick Lajoie
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Rebecca S Shapiro
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G2W1, Canada
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Lee S, Nam M, Lee AR, Lee J, Woo J, Kang NS, Balupuri A, Lee M, Kim SY, Ro H, Choi YW, Kim DU, Hoe KL. Systematic Target Screening Revealed That Tif302 Could Be an Off-Target of the Antifungal Terbinafine in Fission Yeast. Biomol Ther (Seoul) 2021; 29:234-247. [PMID: 33223513 PMCID: PMC7921855 DOI: 10.4062/biomolther.2020.166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 10/12/2020] [Accepted: 10/13/2020] [Indexed: 11/22/2022] Open
Abstract
We used a heterozygous gene deletion library of fission yeasts comprising all essential and non-essential genes for a microarray screening of target genes of the antifungal terbinafine, which inhibits ergosterol synthesis via the Erg1 enzyme. We identified 14 heterozygous strains corresponding to 10 non-essential [7 ribosomal-protein (RP) coding genes, spt7, spt20, and elp2] and 4 essential genes (tif302, rpl2501, rpl31, and erg1). Expectedly, their erg1 mRNA and protein levels had decreased compared to the control strain SP286. When we studied the action mechanism of the non-essential target genes using cognate haploid deletion strains, knockout of SAGA-subunit genes caused a down-regulation in erg1 transcription compared to the control strain ED668. However, knockout of RP genes conferred no susceptibility to ergosterol-targeting antifungals. Surprisingly, the RP genes participated in the erg1 transcription as components of repressor complexes as observed in a comparison analysis of the experimental ratio of erg1 mRNA. To understand the action mechanism of the interaction between the drug and the novel essential target genes, we performed isobologram assays with terbinafine and econazole (or cycloheximide). Terbinafine susceptibility of the tif302 heterozygous strain was attributed to both decreased erg1 mRNA levels and inhibition of translation. Moreover, Tif302 was required for efficacy of both terbinafine and cycloheximide. Based on a molecular modeling analysis, terbinafine could directly bind to Tif302 in yeasts, suggesting Tif302 as a potential off-target of terbinafine. In conclusion, this genome-wide screening system can be harnessed for the identification and characterization of target genes under any condition of interest.
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Affiliation(s)
- Sol Lee
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Miyoung Nam
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Ah-Reum Lee
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Jaewoong Lee
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Jihye Woo
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Nam Sook Kang
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Anand Balupuri
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Minho Lee
- Department of Life Science, Dongguk University-Seoul, Goyang 10326, Republic of Korea
| | - Seon-Young Kim
- Personalized Genomic Research Center, Korea Research Institute of Bioscience & Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
| | - Hyunju Ro
- Department of Biological Science, College of Bioscience & Biotechnology, Chungnam National University, Daejeon 34134, Republic of Korea
| | | | - Dong-Uk Kim
- Rare Disease Research Center, Korea Research Institute of Bioscience & Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
| | - Kwang-Lae Hoe
- Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
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Regulation of Ergosterol Biosynthesis in Saccharomyces cerevisiae. Genes (Basel) 2020; 11:genes11070795. [PMID: 32679672 PMCID: PMC7397035 DOI: 10.3390/genes11070795] [Citation(s) in RCA: 191] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 07/06/2020] [Accepted: 07/13/2020] [Indexed: 12/14/2022] Open
Abstract
Ergosterol is an essential component of fungal cell membranes that determines the fluidity, permeability and activity of membrane-associated proteins. Ergosterol biosynthesis is a complex and highly energy-consuming pathway that involves the participation of many enzymes. Deficiencies in sterol biosynthesis cause pleiotropic defects that limit cellular proliferation and adaptation to stress. Thereby, fungal ergosterol levels are tightly controlled by the bioavailability of particular metabolites (e.g., sterols, oxygen and iron) and environmental conditions. The regulation of ergosterol synthesis is achieved by overlapping mechanisms that include transcriptional expression, feedback inhibition of enzymes and changes in their subcellular localization. In the budding yeast Saccharomyces cerevisiae, the sterol regulatory element (SRE)-binding proteins Upc2 and Ecm22, the heme-binding protein Hap1 and the repressor factors Rox1 and Mot3 coordinate ergosterol biosynthesis (ERG) gene expression. Here, we summarize the sterol biosynthesis, transport and detoxification systems of S. cerevisiae, as well as its adaptive response to sterol depletion, low oxygen, hyperosmotic stress and iron deficiency. Because of the large number of ERG genes and the crosstalk between different environmental signals and pathways, many aspects of ergosterol regulation are still unknown. The study of sterol metabolism and its regulation is highly relevant due to its wide applications in antifungal treatments, as well as in food and pharmaceutical industries.
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Prigent M, Chaillot J, Tisserand H, Boy-Marcotte E, Cuif MH. Three members of the yeast N-BAR proteins family form heterogeneous lattices in vivo and interact differentially with two RabGAP proteins. Sci Rep 2020; 10:1698. [PMID: 32015451 PMCID: PMC6997364 DOI: 10.1038/s41598-020-58606-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 01/08/2020] [Indexed: 11/26/2022] Open
Abstract
The yeast N-BAR (Bin/Amphiphysin/Rvs167) protein Rvs167 is recruited by the Rab GTPase Activating Proteins (RabGAP) Gyp5 and Gyl1 to the tip of small buds to act in exocytosis. Investigating other N-BAR proteins involved in Gyp5/Gyl1/Rvs167 complexes, we found that Rvs161, an Rvs167 paralog, is absent from the complexes formed at the tip of small buds. Immunoprecipitation and Bimolecular Fluorescence Complementation (BiFC) analysis show that both Rvs167 and Rvs161 interact in vivo with Gvp36, an N-BAR protein. Rvs167 molecules also interact independently of Rvs161 and Gvp36. Rvs167/Rvs167 and Rvs167/Gyp5 interactions predominate over other combinations at the tip of small buds, suggesting that N-BAR lattices enriched in Rvs167 molecules form at these sites. By combining BiFC with markers specific to each organelle, we analyzed systematically in living cells the locations of the BiFC signals generated by combinations of the three N-BAR proteins. We show that the BiFC signals differ according to organelle and cell site, strongly suggesting heterogeneity in the composition of N-BAR protein lattices in vivo. Our results reveal that the organization of N-BAR protein lattices in vivo is complex and are consistent with N-BAR proteins forming various types of dimers and lattices of variable composition.
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Affiliation(s)
- Magali Prigent
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Julien Chaillot
- Institut sur la Nutrition et les Aliments Fonctionnels (INAF), Université Laval, 2440 Boulevard Hochelaga, Québec, QC, G1V 0A6, Canada
| | - Hélène Tisserand
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Emmanuelle Boy-Marcotte
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Marie-Hélène Cuif
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
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Evidence that Ergosterol Biosynthesis Modulates Activity of the Pdr1 Transcription Factor in Candida glabrata. mBio 2019; 10:mBio.00934-19. [PMID: 31186322 PMCID: PMC6561024 DOI: 10.1128/mbio.00934-19] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A likely contributor to the increased incidence of non-albicans candidemias involving Candida glabrata is the ease with which this yeast acquires azole resistance, in large part due to induction of the ATP-binding cassette transporter-encoding gene CDR1. Azole drugs lead to induction of Pdr1 transactivation, with a central model being that this factor binds these drugs directly. Here we provide evidence that Pdr1 is activated without azole drugs by the use of genetic means to inhibit expression of azole drug target-encoding gene ERG11. These acute reductions in Erg11 levels lead to elevated Pdr1 activity even though no drug is present. A key transcriptional regulator of the ERG pathway, Upc2A, is shown to directly bind to the PDR1 and CDR1 promoters. We interpret these data as support for the view that Pdr1 function is responsive to ergosterol biosynthesis and suggest that this connection reveals the normal physiological circuitry in which Pdr1 participates. A crucial limitation in antifungal chemotherapy is the limited number of antifungal drugs currently available. Azole drugs represent the most commonly used chemotherapeutic, and loss of efficacy of these drugs is a major risk factor in successful treatment of a variety of fungal diseases. Candida glabrata is a pathogenic yeast that is increasingly found associated with bloodstream infections, a finding likely contributed to by its proclivity to develop azole drug resistance. C. glabrata often acquires azole resistance via gain-of-function (GOF) mutations in the transcription factor Pdr1. These GOF forms of Pdr1 drive elevated expression of target genes, including the ATP-binding cassette transporter-encoding CDR1 locus. GOF alleles of PDR1 have been extensively studied, but little is known of how Pdr1 is normally regulated. Here we test the idea that reduction of ergosterol biosynthesis (as occurs in the presence of azole drugs) might trigger activation of Pdr1 function. Using two different means of genetically inhibiting ergosterol biosynthesis, we demonstrated that Pdr1 activity and target gene expression are elevated in the absence of azole drug. Blocks at different points in the ergosterol pathway lead to Pdr1 activation as well as to induction of other genes in this pathway. Delivery of the signal from the ergosterol pathway to Pdr1 involves the transcription factor Upc2A, an ERG gene regulator. We show that Upc2A binds directly to the PDR1 and CDR1 promoters. Our studies argue for a physiological link between ergosterol biosynthesis and Pdr1-dependent gene regulation that is not restricted to efflux of azole drugs.
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