The zinc cluster transcription factor Ahr1p directs Mcm1p regulation of Candida albicans adhesion
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ABSTRACT: Biofilm development by Candida albicans requires cell adhesion for the initial establishment of the biofilm and the continued stability after hyphal development occurs; however, the regulation of the process has not been fully established. Using chromatin immunoprecipitation coupled to microarray analysis (ChIP-chip) we have characterized a regulon containing the Mcm1p factor that is required for the initial surface adhesion during biofilm formation. In the yeast Saccharomyces cerevisiae several Mcm1p regulons have been characterized in which regulatory specificity is achieved through co-factors binding a sequence adjacent to the Mcm1p-binding site. This new Mcm1p regulon in C. albicans also requires a co-factor, which we identify as the transcription factor Ahr1p. However, in contrast to the other yeast regulons, Ahr1p alone binds the target promoters, which include several key adhesion genes, and recruits Mcm1p to these sites. Through transcription profiling and qPCR analysis, we demonstrate that this Ahr1p-Mcm1p complex directly activates these adhesion genes. When the regulon was disrupted by deleting AHR1, the strain displayed reduced adherence to a polystyrene surface. We also demonstrate a role for the regulon in hyphal growth and in virulence. Our work thus establishes a new mechanism of Mcm1p-directed regulation distinct from those observed for other Mcm1p co-regulators. We performed genome wide occupancy experiments (YPD, 30oC) with Ahr1p and Mcm1p to determine their binding sites. To confirm an interaction between the two factors we also performed genome wide occupancy with Mcm1p in an ahr1 deletion strain. To complement with genome wide occupancy experiments, we performed a transcription profile with an ahr1 deletion strain under yeast conditions (YPD, 30oC).
Project description:In this study, we have investigated Mediator function in the human fungal pathogen C. albicans. An initial screening of conditionally regulated Mediator subunits showed that the Med7 of C. albicans was not essential, in contrast to the situation noted for Saccharomyces cerevisiae. While loss of CaMed7 did not lead to loss of viability under normal growth conditions, it dramatically influenced the pathogenM-bM-^@M-^Ys ability to grow in different carbon sources, to form hyphae and biofilms, and to colonize the gastrointestinal tracts of mice. We used location profiling to determine Mediator binding under yeast and hyphal morphologies characterized by different transcription profiles. We observed a core set of specific and common genes bound by Med7 under both conditions; this specific core set is expanded considerably during hyphal growth, supporting the idea that Mediator binding correlates with changes in transcriptional activity and that this binding is condition specific. Med7 bound not only in the promoter regions of active genes but also of inactive genes and within coding regions and at the 3M-bM-^@M-^Y ends of genes. By combining genome-wide location profiling, expression analyses and phenotyping, we have identified different Med7 regulons including genes related to glycolysis and the Filamentous Growth Regulator family. We performed genome-wide occupancy experiments (YPD, 30oC and YPD, 37oC) with Med7p to determine its binding sites.
Project description:Biofilm development by Candida albicans requires cell adhesion for the initial establishment of the biofilm and the continued stability after hyphal development occurs; however, the regulation of the process has not been fully established. Using chromatin immunoprecipitation coupled to microarray analysis (ChIP-chip) we have characterized a regulon containing the Mcm1p factor that is required for the initial surface adhesion during biofilm formation. In the yeast Saccharomyces cerevisiae several Mcm1p regulons have been characterized in which regulatory specificity is achieved through co-factors binding a sequence adjacent to the Mcm1p-binding site. This new Mcm1p regulon in C. albicans also requires a co-factor, which we identify as the transcription factor Ahr1p. However, in contrast to the other yeast regulons, Ahr1p alone binds the target promoters, which include several key adhesion genes, and recruits Mcm1p to these sites. Through transcription profiling and qPCR analysis, we demonstrate that this Ahr1p-Mcm1p complex directly activates these adhesion genes. When the regulon was disrupted by deleting AHR1, the strain displayed reduced adherence to a polystyrene surface. We also demonstrate a role for the regulon in hyphal growth and in virulence. Our work thus establishes a new mechanism of Mcm1p-directed regulation distinct from those observed for other Mcm1p co-regulators.
Project description:So far, there is no known regulatory circuits that mediate filamentation of the pathogenic yeast Candida albicans exclusively in response to hypoxia. In this study, we performed a quantitative analysis of gene deletion mutants from different collections of protein kinases and transcriptional regulators to identify specific regulator of the hypoxic filamentation. Our work uncovered two transcription factors, Ahr1 and Tye7, that act as prominent regulators of C. albicans filamentation specifically under hypoxia. In summary, we used genome-wide transcriptional profiling and promoter occupancy to characterize both Ahr1 and Tye7 regulons associated with the hypoxic filamentation in C. albicans.
Project description:So far, there is no known regulatory circuits that mediate filamentation of the pathogenic yeast Candida albicans exclusively in response to hypoxia. In this study, we performed a quantitative analysis of gene deletion mutants from different collections of protein kinases and transcriptional regulators to identify specific regulator of the hypoxic filamentation. Our work uncovered two transcription factors, Ahr1 and Tye7, that act as prominent regulators of C. albicans filamentation specifically under hypoxia. In summary, we used genome-wide transcriptional profiling and promoter occupancy to characterize both Ahr1 and Tye7 regulons associated with the hypoxic filamentation in C. albicans.
Project description:Compared to other model organisms and despite the clinical relevance of the pathogenic yeast Candida albicans, no comprehensive analysis has been done to provide experimental support of its in silico-based genome annotation. Here we have undertaken a genome-wide experimental annotation to accurately uncover the transcriptional landscape of the pathogenic yeast C. albicans using strand-specific high-density tiling arrays. RNAs were purified from cells growing under conditions relevant to C. albicans pathogenicity, including biofilm, lab-grown yeast and serum-induced hyphae as well as cells isolated from the mouse caecum. This work provides a genome-wide experimental validation for a large number of predicted ORFs for which transcription had not been detected by other approaches. Additionally, we identified more than 2000 novel transcriptional segments, including new ORFs and exons, non-coding RNAs (ncRNA) as well as convincing cases of antisense gene transcription. We also characterized the 5’- and 3’-untranslated regions (UTR) of expressed ORFs, and established that genes with long 5’UTRs are significantly enriched in regulatory functions controlling filamentous growth. Furthermore, we found that genomic regions adjacent to telomeres harbor a cluster of expressed ncRNAs. To validate and confirm new ncRNA candidates, we adapted an iterative strategy combining both genome-wide occupancy of the different subunits of RNA polymerases I, II and III, and expression data. This comprehensive approach allowed the identification of different families of ncRNA. In summary, we provide a comprehensive expression atlas that covers relevant C. albicans pathogenic developmental stages in addition to a discovery of new ORF and non-coding genetic elements. We have undertaken a genome-wide experimental annotation to accurately uncover the transcriptional landscape of the pathogenic yeast C. albicans using strand-specific high-density tiling arrays. RNAs were purified from cells growing under conditions relevant to Candida albicans pathogenicity, including biofilm, lab-grown yeast and serum-induced hyphae as well as cells isolated from the mouse caecum. We also adapted a strategy in which genome-wide occupancy of different subunits of RNA polymerases (RNAP) I, II and III, is combined with expression data to annotate ncRNAs resulting from real transcriptional events. For this purpose we have performed ChIP-chip of subunits that represent the three RNAP machines in C. albicans cells growing in rich media (YPD) at 30°C. In this study, we performed peak detection only for RNA Polymerase III (Rpc82p). All detected peaks and their genomic features are included as a supplementary file on the Sample record (GSM561024).
Project description:The capacity to sense and transduce temperature signals pervades all aspects of biology, and temperature exerts powerful control over the development and virulence of diverse pathogens. In the leading fungal pathogen of humans, Candida albicans, temperature has a profound impact on morphogenesis, a key virulence trait. Many cues that induce the transition from yeast to filamentous growth are contingent on a minimum temperature of 37ºC, while further elevatation to 39ºC serves as an independent inducing cue. The molecular chaperone Hsp90 is a key regulator of C. albicans temperature-dependent morphogenesis, as induction of filamentous growth requires relief from Hsp90-mediated repression of the morphogenetic program. Compromise of Hsp90 function genetically, pharmacologically, or by elevated temperature induces filamentation in a manner that depends on protein kinase A (PKA) signaling, but is independent of the terminal transcription factor, Efg1. Here, we determine that despite morphological and regulatory differences, inhibition of Hsp90 induces a transcriptional profile similar to that induced by other filamentation cues, and does so in a manner that is independent of Efg1. Further, we identify Hms1 as a transcriptional regulator required for morphogenesis induced by elevated temperature or compromise of Hsp90 function. Hms1 functions downstream of the cyclin Pcl, and the cyclin-dependent kinase Pho85, both of which are required for temperature-dependent filamentation. Upon Hsp90 inhibition, Hms1 binds to DNA elements involved in filamentous growth, including UME6 and RBT5, and regulates their expression, providing a mechanism through which Pho85, Pcl1, and Hms1 govern morphogenesis. Consistent with the importance of morphogenetic flexibility with virulence, deletion of C. albicans HMS1 attenuates virulence in a metazoan model of infection. Thus, we establish a new mechanism through which Hsp90 orchestrates C. albicans morphogenesis, and define novel regulatory circuitry governing a temperature-dependent developmental program, with broad implications for temperature sensing and virulence of microbial pathogens. Genome-wide occupancy experiments (Chip-CHIP) of FLAG-tagged Hms1p from cells grown in the presence or absence of geldanamycin (GldA). Co-precipitating genomic DNA was labelled and hybridized to whole-genome tiling arrays.
Project description:This SuperSeries is composed of the following subset Series: GSE34255: Pho85, Pcl1, and Hms1 Signaling Governs Candida albicans Morphogenesis Induced by Elevated Temperature or Hsp90 Compromise [mRNA] GSE34938: Pho85, Pcl1, and Hms1 Signaling Governs Candida albicans Morphogenesis Induced by Elevated Temperature or Hsp90 Compromise [ChIP-chip] Refer to individual Series
Project description:This work reports the role of the transcription factor Ahr1 in mediating cell size control in the pathogenic yeast Candida albicans. To investigate the role of Ahr1 at Start, we performed a transcriptional profiling by comparing the transcriptome of G1 phase cells of both WT and ahr1 mutant strains.
Project description:Biofilms with immobilized cells in industrial fermentation are beneficial. Encased in extracellular polymeric substance, cells forming biofilms are regulated by various factors. Nitric oxide (NO), as a signaling molecule, recognized as quorum sensing molecule regulating microbe biofilm formation. Regulation mechanisms of NO on bacteria biofilm have been studied extensively and deeply, while on fungus are rarely studied. In this study, we observed that low concentration of NO enhanced S. cerevisiae biofilm formation. Transcriptional and proteomic analysis revealed that transcription factor MAC1 was activated in biofilm cells under NO treatment. Overexpressed MAC1 increased yeast biofilm formation bypassing regulating the expression level of FLO11. Increased copper and iron contents in NO treated and MAC1 overexpressed cells were not responsible for increased biofilm formation. Among six downstream genes of MAC1, overexpressed CTR1 contributed yeast biofilm formation. Moreover, MAC1 and CTR1 contributed to biofilm cells ethanol resistance resulting from enhanced biofilm. The role of CTR1 protein in yeast biofilm formation may result from its hydrophobic residues in N-terminal extracellular domain. These findings suggested a NO-mediated biofilm formation mechanism that NO regulated expression levels of CTR1 through activating its transcription factor MAC1, leading enhanced biofilm formation.
Project description:Here, we report the comparison of transcriptomes of Anabaena sp. PCC7120 and the FurB(Zur) deletion derivative strain (MN38). Anabaena sp PCC7120 is a cyanobacterium that differentiates specialized nitrogen-fixing cells called heterocysts and that is capable of forming biofilms. Our data showed that the deletion of FurB negativily affected the heterocyst development and the biofilm formation. In addition, the RNA-seq data together with gel retardation assays unveiled that FurB is directly involved in the regulation of several genes related to heterocyst development and biofilm formation and other novel functions different from the ones related to the canonical Zur regulon.