Unknown,Transcriptomics,Genomics,Proteomics

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ChIP-seq analyses of the Aspergillus fumigatus SREBP SrbA

ABSTRACT: The Aspergillus fumigatus sterol regulatory element binding protein (SREBP) SrbA belongs to the basic Helix-Loop-Helix (bHLH) family of transcription factors and is crucial for antifungal drug resistance and virulence. The latter phenotype is especially striking, as loss of SrbA results in complete loss of virulence in murine models of invasive pulmonary aspergillosis (IPA). How fungal SREBPs mediate fungal virulence is unknown, though it has been suggested that lack of growth in hypoxic conditions accounts for the attenuated virulence. To further understand the role of SrbA in fungal infection site pathobiology, chromatin immunoprecipitation followed by massively parallel DNA sequencing (ChIP-seq) was used to identify genes under direct SrbA transcriptional regulation in hypoxia. These results confirmed the direct regulation of ergosterol biosynthesis and iron uptake by SrbA in hypoxia and revealed new roles for SrbA in nitrate assimilation and heme biosynthesis. Moreover, functional characterization of an SrbA target gene with sequence similarity to SrbA identified a new transcriptional regulator of the fungal hypoxia response and virulence, SrbB. SrbB co-regulates genes involved in heme biosynthesis and demethylation of C4 sterols with SrbA in hypoxic conditions. However, SrbB also has regulatory functions independent of SrbA including regulation of carbohydrate metabolism. Loss of SrbB markedly attenuates A. fumigatus virulence, and loss of both SREBPs further reduces in vivo fungal growth. These data suggest that both A. fumigatus SREBPs are critical for hypoxia adaptation and virulence and reveals new insights into SREBPM-bM-^@M-^Ys complex role in infection site adaptation and fungal virulence. 4 hour and 12 hour ChIP experiments were completed. Input control samples for each set were collected.

ORGANISM(S): Aspergillus fumigatus

SUBMITTER: Bridget Barker

PROVIDER: E-GEOD-61974 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Sampangine, a plant-derived alkaloid found in the Annonaceae family, exhibits strong inhibitory activity against the opportunistic fungal pathogens Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. In the present study, transcriptional profiling experiments coupled with the analysis of mutants were performed in an effort to elucidate its mechanism of action. Using Saccharomyces cerevisiae as a model organism, we show that sampangine produces a transcriptional response indicative of hypoxia, altering the expression of genes known to respond to low oxygen conditions. Several additional lines of evidence obtained suggest that these responses could involve effects on heme. First, the hem1 deletion mutant lacking the first enzyme in the heme biosynthetic pathway showed increased sensitivity to sampangine, and exogenously supplied hemin partially rescued the inhibitory activity of sampangine in wild-type cells. In addition, heterozygous mutants with deletions in genes involved in five out of eight steps in the heme biosynthetic pathway showed increased susceptibility to sampangine. Furthermore, spectral analysis of pyridine extracts indicated significant accumulation of free porphyrins in sampangine-treated cells. Transcriptional profiling experiments were also performed in C. albicans to investigate the response of a pathogenic fungal species to sampangine. Taking into account the known differences in the physiological responses of C. albicans and S. cerevisiae to low oxygen, significant correlations were observed between the two transcription profiles suggestive of heme-related defects. Our results indicate that the antifungal activity of the plant alkaloid sampangine is due, at least in part, to perturbations in the biosynthesis or metabolism of heme. Experiment Overall Design: S. cerevisiae S288C cells at OD 0.2 were treated with either sampangine (SMP) at IC50 concentration (1.17 ug/ml), or solvent (0.25% DMSO), allowed to grow to OD 0.5, then harvested and frozen. Three biological replicate samples were analyzed for each treatment.

Project description:Sampangine, a plant-derived alkaloid found in the Annonaceae family, exhibits strong inhibitory activity against the opportunistic fungal pathogens Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. In the present study, transcriptional profiling experiments coupled with the analysis of mutants were performed in an effort to elucidate its mechanism of action. Using Saccharomyces cerevisiae as a model organism, we show that sampangine produces a transcriptional response indicative of hypoxia, altering the expression of genes known to respond to low oxygen conditions. Several additional lines of evidence obtained suggest that these responses could involve effects on heme. First, the hem1 deletion mutant lacking the first enzyme in the heme biosynthetic pathway showed increased sensitivity to sampangine, and exogenously supplied hemin partially rescued the inhibitory activity of sampangine in wild-type cells. In addition, heterozygous mutants with deletions in genes involved in five out of eight steps in the heme biosynthetic pathway showed increased susceptibility to sampangine. Furthermore, spectral analysis of pyridine extracts indicated significant accumulation of free porphyrins in sampangine-treated cells. Transcriptional profiling experiments were also performed in C. albicans to investigate the response of a pathogenic fungal species to sampangine. Taking into account the known differences in the physiological responses of C. albicans and S. cerevisiae to low oxygen, significant correlations were observed between the two transcription profiles suggestive of heme-related defects. Our results indicate that the antifungal activity of the plant alkaloid sampangine is due, at least in part, to perturbations in the biosynthesis or metabolism of heme. C. albicans SC5314 cells at OD 0.2 were treated with either sampangine (SMP) at IC50 concentration (6.13 ug/ml), or solvent (0.25% DMSO), allowed to grow to OD 0.5, then harvested and frozen. Three biological replicate samples were analyzed for each treatment.

Project description:Sampangine, a plant-derived alkaloid found in the Annonaceae family, exhibits strong inhibitory activity against the opportunistic fungal pathogens Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. In the present study, transcriptional profiling experiments coupled with the analysis of mutants were performed in an effort to elucidate its mechanism of action. Using Saccharomyces cerevisiae as a model organism, we show that sampangine produces a transcriptional response indicative of hypoxia, altering the expression of genes known to respond to low oxygen conditions. Several additional lines of evidence obtained suggest that these responses could involve effects on heme. First, the hem1 deletion mutant lacking the first enzyme in the heme biosynthetic pathway showed increased sensitivity to sampangine, and exogenously supplied hemin partially rescued the inhibitory activity of sampangine in wild-type cells. In addition, heterozygous mutants with deletions in genes involved in five out of eight steps in the heme biosynthetic pathway showed increased susceptibility to sampangine. Furthermore, spectral analysis of pyridine extracts indicated significant accumulation of free porphyrins in sampangine-treated cells. Transcriptional profiling experiments were also performed in C. albicans to investigate the response of a pathogenic fungal species to sampangine. Taking into account the known differences in the physiological responses of C. albicans and S. cerevisiae to low oxygen, significant correlations were observed between the two transcription profiles suggestive of heme-related defects. Our results indicate that the antifungal activity of the plant alkaloid sampangine is due, at least in part, to perturbations in the biosynthesis or metabolism of heme. GSE10073: Gene expression response to the antifungal compound sampangine in S. cerevisiae GSE10075: Gene expression response to the antifungal compound sampangine in C. albicans Keywords: SuperSeries Refer to individual Series

Project description:Iron is an essential cofactor for a wide range of cellular processes. Previous studies have shown that siderophore-mediated uptake and intracellular handling of iron are crucial for virulence of Aspergillus fumigatus. Here we show that the bzip-type transcription factor HapX plays a crucial role in the transcriptional remodeling required for adaption to iron starvation in this opportunistic fungal pathogen. HapX was found to be interconnected in a negative feed-back loop with the previously identified iron regulator SreA: SreA repressed expression of hapX during iron sufficiency and HapX repressed sreA during iron starvation. Genome-wide transcriptional profiling and analysis of selected metabolites (protophorphyrine IX, siderophores and amino acids) indicated extensive metabolic remodeling in response to iron starvation. HapX was found to participate in both, repression and activation of genes during iron starvation. HapX was in particular required for repression of iron-dependent and mitochondrial-localized activities including respiration, TCA cycle, amino acid metabolism, iron-sulfur-cluster biosynthesis and heme biosynthesis. Pathways positively affected by HapX included production of siderophores and the ribotoxin and major allergen AspF1. Analysis of the free amino acid pool revealed HapX-dependent coordination of the production of siderophores with the supply of its precursor ornithine. Consistent with the hapX expression pattern, HapX-deficiency was deleterious with respect to growth rate and conidiation during iron depleted but not iron-replete conditions. HapX-deficiency caused significant attenuation of virulence in a murine model aspergillosis underlining that A. fumigatus faces iron starvation in the host and that the HapX-dependent metabolic reprogramming is therefore crucial for virulence. A. fumigatus 293 and hapX mutants were grown in the presence and absence of iron and in cultures shifted from no iron to iron-containing conditions after 1 h incubation. Hybridizations were performed with biological replicates for wt vs hapX +/- iron. For the iron-shift experiments, there were biological replicates for wt in both conditions and for hapX in -iron but there was only a single biological sample for hapX iron-shift sample. All hybs were performed with flip-dye pairs.

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ChIP-seq analyses of the Aspergillus fumigatus SREBP SrbA

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