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Loss-of-function ROX1 mutations suppress the fluconazole susceptibility of upc2A∆ mutation in Candida glabrata, implicating additional positive regulators of ergosterol biosynthesis

ABSTRACT: Two of the major classes of antifungal drugs in clinical use target ergosterol biosynthesis. Despite its importance, our understanding of the transcriptional regulation of ergosterol biosynthesis genes in pathogenic fungi is essentially limited to the role of hypoxia and sterol-stress induced transcription factors such as Upc2 and Upc2A as well as homologs of Sterol Response Element Binding (SREB) factors. To identify additional regulators of ergosterol biosynthesis in Candida glabrata, an important human fungal pathogen with reduced susceptibility to ergosterol biosynthesis inhibitors relative to other Candida spp., we used a serial passaging strategy to isolate suppressors of the fluconazole hypersusceptibility of a upc2A∆ deletion mutant. This led to the identification of loss of function mutants in two genes: ROX1, the homolog of a hypoxia gene transcriptional suppressor in Saccharomyces cerevisiae, and CST6, a transcription factor that is involved in the regulation of carbon dioxide response in C. glabrata. Here, we describe a detailed analysis of the genetic interaction of ROX1 and UPC2A. In the presence of fluconazole, loss of Rox1 function restores ERG11 expression to the upc2A∆ mutant and inhibits the expression of ERG3 and ERG6, leading to increased levels or ergosterol and decreased levels of the toxic sterol, 14α methyl-ergosta-8,24(28)-dien-3β, 6α-diol, relative to upc2A∆. Our observations establish that Rox1 is a negative regulator of ERG gene biosynthesis and indicate that a least one additional positive transcriptional regulator of ERG gene biosynthesis must be present in C. glabrata.

ORGANISM(S): Nakaseomyces glabratus

PROVIDER: GSE191145 | GEO | 2021/12/20

REPOSITORIES: GEO

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RNA-seq Analysis of Wild-Type and G898D UPC2A Transcriptomes [G898D UPC2A transcriptome]

Project description:Purpose: Determine the number of genes that respond to the presence of a gain-of-function mutant form of the UPC2A transcription factor in Candida glabrata. Methods: Prepare total RNA from wild-type and gain-of-function G898D UPC2A cells. Use standard RNA-seq to evaluate and compare the transcriptomic changes caused by this allele of UPC2A. Results: Although a clear increase was seen in fluconazole resistance conferred by the G898D UPC2A allele, elevated transcription was only observed for 11 genes with 9 of these involved in ergosterol biosynthesis. Conclusions: The presence of the G898D UPC2A allele led to elevated constitutive transcription for genes involved in ergosterol biosynthesis.

2021-09-23 | GSE182490 | GEO

Copper acts synergistically with fluconazole in Candida glabrata by compromising drug efflux, zinc homeostasis and sterol metabolism

Project description:In this study we used a transcriptomic approach to study the molecular determinants of the synergy between copper and fluconazole, in Candida glabrata, the second most frequent cause of invasive candidiasis. We demonstrate that copper acts together with fluconazole by downregulating three distinct pathways: azole efflux, ergosterol biosynthesis and zinc homeostasis. Coincidently, all these pathways are important for C. glabrata to cope with fluconazole stress. Therefore, when copper and fluconazole are combined cells fail to detoxify this drug and accumulate toxic methylated intermediates of sterol metabolism. This accumulation, possibly together with copper-induced lipid damages, should affect the activity of plasma membrane transporters, which impedes zinc uptake, leading to zinc depletion

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Limosilactobacillus fermentum Limits Candida glabrata Growth by Ergosterol Depletion

Project description:Candida glabrata is a human-associated opportunistic fungal pathogen. It shares its niche with Lactobacillus spp. in the gastrointestinal and vaginal tract. In fact, Lactobacillus species are thought to competitively prevent Candida overgrowth. We investigated the molecular aspects of this antifungal effect by analyzing the interaction of C. glabrata strains with Limosilactobacillus fermentum. From a collection of clinical C. glabrata isolates, we identified strains with different sensitivities to L. fermentum in coculture. We analyzed the variation of their expression pattern to isolate the specific response to L. fermentum. C. glabrata-L. fermentum coculture induced genes associated with ergosterol biosynthesis, weak acid stress, and drug/chemical stress. L. fermentum coculture depleted C. glabrata ergosterol. The reduction of ergosterol was dependent on the Lactobacillus species, even in coculture with different Candida species. We found a similar ergosterol-depleting effect with other lactobacillus strains (Lactobacillus crispatus and Lactobacillus rhamosus) on Candida albicans, Candida tropicalis, and Candida krusei. The addition of ergosterol improved C. glabrata growth in the coculture. Blocking ergosterol synthesis with fluconazole increased the susceptibility against L. fermentum, which was again mitigated by the addition of ergosterol. In accordance, a C. glabrata Derg11 mutant, defective in ergosterol biosynthesis, was highly sensitive to L. fermentum. In conclusion, our analysis indicates an unexpected direct function of ergosterol for C. glabrata proliferation in coculture with L. fermentum.

2023-02-08 | GSE202656 | GEO

Evolutionary divergence in the fungal response to fluconazole revealed by soft clustering (S. cerevisiae, C. glabrata, K. lactis)

Project description:Fungal infections are an emerging health risk, especially those involving yeast that are resistant to antifungal agents. To understand the range of mechanisms by which yeasts can respond to anti-fungals, we compared gene expression patterns across three evolutionarily distant species - Saccharomyces cerevisiae, Candida glabrata and Kluyveromyces lactis - over time following fluconazole exposure. Conserved and diverged expression patterns were identified using a novel soft clustering algorithm that concurrently clusters data from all species while incorporating sequence orthology. The analysis suggests complementary strategies for coping with ergosterol depletion by azoles - Saccharomyces imports exogenous ergosterol, Candida exports fluconazole, while Kluyveromyces does neither leading to extreme sensitivity. In support of this hypothesis we find that only Saccharomyces becomes more azole resistant in ergosterol-supplemented media; that this depends on sterol importers Aus1 and Pdr11; and that transgenic expression of sterol importers in Kluyveromyces alleviates its drug sensitivity. We have compared the dynamic transcriptional responses of three diverse yeast species to fluconazole treatment using a novel clustering algorithm. This approach revealed significant divergence among regulatory programs associated with fluconazole sensitivity. In future, such approaches might be used to survey a wider range of species, drug concentrations and stimuli to reveal conserved and divergent molecular response pathways.

2010-07-08 | GSE15710 | GEO

Evolutionary rewiring of the ROX genes controlling hypoxic response in yeasts

Project description:Unusually among fungi, Saccharomyces cerevisiae is able to grow in environments containing almost no oxygen. A major feature of its response to hypoxia is a transition in expression from aerobic to hypoxic genes, which often code for duplicated isoforms of the same protein. In aerobic conditions, expression of the hypoxic gene set is repressed by the HMG domain protein Rox1. Here, we examined the evolution of ROX1 and related genes in the subphylum Saccharomycotina and find that a substantial reorganization of hypoxic gene regulation occurred during yeast evolution. S. cerevisiae lost ROX2, an ancient paralog of ROX1, which is almost universally present in other yeast species. ROX2 is orthologous to Candida albicans RFG1, a regulator of filamentous growth. Many yeasts, such as Candida glabrata, lack ROX1 and contain only ROX2. Others such as Naumovozyma castellii retain both genes. Although the ancestral function of ROX2 is uncertain, we find that it is not a regulator of hypoxic genes except in C. glabrata where it has taken over this function from the absent ROX1. We also find that N. castellii has a greatly attenuated transcriptional response to hypoxia as compared to other species, but that the ergosterol pathway which is normally induced by hypoxia can be induced by cobalt chloride stress in N. castellii.

2018-07-31 | GSE75235 | GEO

RNA-sequencing analysis of fluconazole-treated wild-type and upc2A null cells [Fluconazole]

Project description:Purpose: Compare the fluconazole-induced transcriptome of isogenic wild-type and upc2A null cells. Methods: Prepare total RNA from wild-type and upc2A null cells grown under unstressed conditions or challenged with 50 microgram/ml fluconazole for 6 hours. Use standard RNA-seq to evaluate and compare the transcriptomic changes caused by fluconazole in the presence or absence of UPC2A. Results: These data established that over 100 genes were induced by fluconazole in a UPC2A-dependent manner. However, most fluconazole-induced genes (>500) did not require the presence of UPC2A. Fluconazole-induced genes included the expected genes involved in ergosterol biosynthesis but also large number of plasma membrane-localized transporters. Conclusions: These data suggest that Upc2A provided transcriptional co-regulation between membrane transporters and the lipid environment in which these proteins function. A significant portion of the fluconazole-induced transcriptome does not require the presence of Upc2A, suggesting the presence of other transcriptional circuits responsive to this pharmacologic block of ergosterol biosynthesis.

2021-09-23 | GSE182489 | GEO

Evolutionary divergence in the fungal response to fluconazole revealed by soft clustering (S. cerevisiae, C. glabrata, K. lactis)

2010-07-08 | E-GEOD-15710 | biostudies-arrayexpress

Loss-of-function ROX1 mutations suppress the fluconazole susceptibility of upc2A∆ mutation in Candida glabrata, implicating additional positive regulators of ergosterol biosynthesis

Project description:Loss-of-function ROX1 mutations suppress the fluconazole susceptibility of upc2A∆ mutation in Candida glabrata, implicating additional positive regulators of ergosterol biosynthesis

| PRJNA789874 | ENA

ChIP-seq analysis of transcription factor Upc2A binding across the Candida glabrata genome [Upc2A ChIP-seq]

Project description:To determine the genomic binding sites for the Candida glabrata transcription factor Upc2A, we utilized three different strains. One was the wild-type KKY2001 which contains a wild-type copy of UPC2A but lacks any HA tag. The other two are both derived from KKY2001 but contain a 3X HA tag immediately after the start codon of UPC2A. These strains are BVGC82 and BVGC84, respectively. Both contain a single copy of a loxP element located 252 bp downstream from the UPC2A stop codon. BVGC82 contains a wild-type copy of the UPC2A gene while BVGC84 contains a mutant form of UPC2A (G898D) that confers elevated resistance to fluconazole. ChIP was performed with anti-HA antibodies in all cases. Strains containing the wild-type UPC2A gene (no HA tag) are referred to as C1 and C2. Strains containing the 3X HA epitope tag at the N-terminus of the wild-type UPC2A gene are referred to as wt1 and wt2. These same strains challenged with fluconazole prior to ChIP are referred to as wtf1 and wtf2. The strain containing the G898D UPC2A allele are referred to as M1 and M2 (no fluconazole challenge) and MF1 and MF2 (with fluconazole challenge.

2021-09-23 | GSE182488 | GEO

Set1-mediated histone H3K4 methylation is conserved and required for azole induction of ergosterol biosynthesis genes and antifungal drug resistance in Candida glabrata

Project description:Fungal infections are a major health concern because of limited antifungal drugs and development of drug resistance. Candida can develop azole drug resistance by overexpression of drug efflux pumps or mutating ERG11, the target of azoles. However, the role of epigenetic histone modifications in azole-induced gene expression and drug resistance is poorly understood in Candida glabrata. In this study, we show that Set1 mediates histone H3K4 methylation in C. glabrata. In addition, loss of SET1 and histone H3K4 methylation increases azole susceptibility in both C. glabrata and S. cerevisiae. This increase in azole susceptibility in S. cerevisiae and C. glabrata strains lacking SET1 is due to distinct mechanisms. For S. cerevisiae, loss of SET1 decreased the expression and function of the efflux pump Pdr5, but not ERG11 expression under azole treatment. In contrast, loss of SET1 in C. glabrata does not alter expression or function of efflux pumps. However, RNA sequencing revealed that C. glabrata Set1 is necessary for azole-induced expression of all 12 genes in the late ergosterol biosynthesis pathway, including ERG11 and ERG3. Furthermore, chromatin immunoprecipitation analysis shows histone H3K4 trimethylation increases upon azole-induced ERG gene expression. In addition, high performance liquid chromatography analysis indicated Set1 is necessary for maintaining proper ergosterol levels under azole treatment. Clinical isolates lacking SET1 were also hypersusceptible to azoles which is attributed to reduced ERG11 expression but not defects in drug efflux. Overall, Set1 contributes to azole susceptibility in a species-specific manner by altering the expression and consequently disrupting pathways known for mediating drug resistance.

2022-07-28 | GSE209637 | GEO

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