scholarly journals Regulation of Cdc42 GTPase Activity in the Formation of Hyphae inCandida albicans

2007 ◽  
Vol 18 (1) ◽  
pp. 265-281 ◽  
Author(s):  
Helen Court ◽  
Peter Sudbery
Keyword(s):  
Fungal Pathogen ◽  
Germ Tube ◽  
Gtpase Activity ◽  
Negative Regulators ◽  
Human Fungal Pathogen ◽  
Gtpase Activating Proteins ◽  
Characteristic Features ◽  
Increased Activity ◽  
Intrinsic Gtpase Activity ◽  
Incandida Albicans

The human fungal pathogen Candida albicans can switch between yeast, pseudohyphal, and hyphal morphologies. To investigate whether the distinctive characteristics of hyphae are due to increased activity of the Cdc42 GTPase, strains lacking negative regulators of Cdc42 were constructed. Unexpectedly, the deletion of the Cdc42 Rho guanine dissociation inhibitor RDI1 resulted in reduced rather than enhanced polarized growth. However, when cells lacking both Cdc42 GTPase-activating proteins, encoded by RGA2 and BEM3, were grown under pseudohyphal-promoting conditions the bud was highly elongated and lacked a constriction at its base, so that its shape resembled a hyphal germ tube. Moreover, a Spitzenkörper was present at the bud tip, a band of disorganized septin was present at bud base, true septin rings formed within the bud, and nuclei migrated out of the mother cell before the first mitosis. These are all characteristic features of a hyphal germ tube. Intriguingly, we observed hyphal-specific phosphorylation of Rga2, suggesting a possible mechanism for Cdc42 activation during normal hyphal development. In contrast, expression of Cdc42G12V, which is constitutively GTP bound because it lacks GTPase activity, resulted in swollen cells with prominent and stable septin bars. These results suggest the development of hyphal-specific characteristics is promoted by Cdc42-GTP in a process that also requires the intrinsic GTPase activity of Cdc42.

scholarly journals The 5’ untranslated region of theEFG1transcript promotes its translation to regulate hyphal morphogenesis inCandida albicans

2018 ◽  
Author(s):  
Prashant R. Desai ◽  
Klaus Lengeler ◽  
Mario Kapitan ◽  
Silas Matthias Janßen ◽  
Paula Alepuz ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Fungal Pathogen ◽  
Regulatory Mechanisms ◽  
Untranslated Regions ◽  
Regulatory Sequence ◽  
Transcriptional Level ◽  
Human Fungal Pathogen ◽  
Hyphal Morphogenesis ◽  
Cellular Morphogenesis ◽  
Incandida Albicans

ABSTRACTExtensive 5’ untranslated regions (UTR) are a hallmark of transcripts determining hyphal morphogenesis inCandida albicans.The major transcripts of theEFG1gene, which are responsible for cellular morphogenesis and metabolism, contain a 5’ UTR of up to 1170 nt. Deletion analyses of the 5’ UTR revealed a 218 nt sequence that is required for production of the Efg1 protein and its functions in filamentation, without lowering the level and integrity of theEFG1transcript. Polysomal analyses revealed that the 218 nt 5’ UTR sequence is required for efficient translation of the Efg1 protein. Replacement of theEFG1ORF by the heterologous reporter geneCaCBGlucconfirmed the positive regulatory importance of the identified 5’ UTR sequence. In contrast to other reported transcripts containing extensive 5’ UTR sequences, these results indicate the positive translational function of the 5’ UTR sequence in theEFG1transcript, which is observed in context of the nativeEFG1promoter. The results suggest that the 5’ UTR recruits regulatory factors, possibly during emergence of the native transcript, which aid in translation of theEFG1transcript.IMPORTANCEMany of the virulence traits that makeCandida albicansan important human fungal pathogen are regulated on a transcriptional level. Here we report an important regulatory contribution of translation, which is exerted by the extensive 5’ untranslated regulatory sequence (5’ UTR) of the transcript for the protein Efg1, which determines growth, metabolism and filamentation in the fungus. Presence of the 5’ UTR is required for efficient translation of Efg1, to promote filamentation. Because transcripts for many relevant regulators contain extensive 5’ UTR sequences, it appears that virulence ofC. albicansdepends on the combination of transcriptional and translation regulatory mechanisms.

scholarly journals The 5′ Untranslated Region of theEFG1Transcript Promotes Its Translation To Regulate Hyphal Morphogenesis inCandida albicans

mSphere ◽  
2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Prashant R. Desai ◽  
Klaus Lengeler ◽  
Mario Kapitan ◽  
Silas Matthias Janßen ◽  
Paula Alepuz ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Fungal Pathogen ◽  
Untranslated Regions ◽  
Regulatory Sequence ◽  
Transcriptional Level ◽  
Content Type ◽  
Reading Frame ◽  
Human Fungal Pathogen ◽  
Hyphal Morphogenesis ◽  
Incandida Albicans

ABSTRACTExtensive 5′ untranslated regions (UTR) are a hallmark of transcripts determining hyphal morphogenesis inCandida albicans. The major transcripts of theEFG1gene, which are responsible for cellular morphogenesis and metabolism, contain a 5′ UTR of up to 1,170 nucleotides (nt). Deletion analyses of the 5′ UTR revealed a 218-nt sequence that is required for production of the Efg1 protein and its functions in filamentation, without lowering the level and integrity of theEFG1transcript. Polysomal analyses revealed that the 218-nt 5′ UTR sequence is required for efficient translation of the Efg1 protein. Replacement of theEFG1open reading frame (ORF) by the heterologous reporter geneCaCBGlucconfirmed the positive regulatory importance of the identified 5′ UTR sequence. In contrast to other reported transcripts containing extensive 5′ UTR sequences, these results indicate the positive translational function of the 5′ UTR sequence in theEFG1transcript, which is observed in the context of the nativeEFG1promoter. It is proposed that the 5′ UTR recruits regulatory factors, possibly during emergence of the native transcript, which aid in translation of theEFG1transcript.IMPORTANCEMany of the virulence traits that makeCandida albicansan important human fungal pathogen are regulated on a transcriptional level. Here, we report an important regulatory contribution of translation, which is exerted by the extensive 5′ untranslated regulatory sequence (5′ UTR) of the transcript for the protein Efg1, which determines growth, metabolism, and filamentation in the fungus. The presence of the 5′ UTR is required for efficient translation of Efg1, to promote filamentation. Because transcripts for many relevant regulators contain extensive 5′ UTR sequences, it appears that the virulence ofC. albicansdepends on the combination of transcriptional and translational regulatory mechanisms.

scholarly journals InCandida albicans, phosphorylation of Exo84 by Cdk1-Hgc1 is necessary for efficient hyphal extension

2014 ◽  
Vol 25 (7) ◽  
pp. 1097-1110 ◽  
Author(s):  
David Caballero-Lima ◽  
Peter E. Sudbery
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Fungal Pathogen ◽  
Mammalian Cells ◽  
Secretory Vesicles ◽  
Multiprotein Complex ◽  
Human Fungal Pathogen ◽  
Target Sites ◽  
Surface Expansion ◽  
Incandida Albicans

The exocyst, a conserved multiprotein complex, tethers secretory vesicles before fusion with the plasma membrane; thus it is essential for cell surface expansion. In both Saccharomyces cerevisiae and mammalian cells, cell surface expansion is halted during mitosis. In S. cerevisiae, phosphorylation of the exocyst component Exo84 by Cdk1-Clb2 during mitosis causes the exocyst to disassemble. Here we show that the hyphae of the human fungal pathogen Candida albicans continue to extend throughout the whole of mitosis. We show that CaExo84 is phosphorylated by Cdk1, which is necessary for efficient hyphal extension. This action of Cdk1 depends on the hyphal-specific cyclin Hgc1, the homologue of G1 cyclins in budding yeast. Phosphorylation of CaExo84 does not alter its localization but does alter its affinity for phosphatidylserine, allowing it to recycle at the plasma membrane. The different action of Cdk1 on CaExo84 and ScExo84 is consistent with the different locations of the Cdk1 target sites in the two proteins. Thus this conserved component of polarized growth has evolved so that its phosphoregulation mediates the dramatically different patterns of growth shown by these two organisms.

scholarly journals The Yak1 Kinase Is Involved in the Initiation and Maintenance of Hyphal Growth inCandida albicans

2008 ◽  
Vol 19 (5) ◽  
pp. 2251-2266 ◽  
Author(s):  
Sophie Goyard ◽  
Philipp Knechtle ◽  
Murielle Chauvel ◽  
Adeline Mallet ◽  
Marie-Christine Prévost ◽  
...  
Keyword(s):  
Fungal Pathogen ◽  
Transcriptional Profiling ◽  
Hyphal Growth ◽  
Oropharyngeal Candidiasis ◽  
Human Fungal Pathogen ◽  
Dual Specificity ◽  
Genome Wide ◽  
Pharmacologic Inhibition ◽  
Incandida Albicans

Members of the dual-specificity tyrosine-phosphorylated and regulated kinase (DYRK) family perform a variety of functions in eukaryotes. We used gene disruption, targeted pharmacologic inhibition, and genome-wide transcriptional profiling to dissect the function of the Yak1 DYRK in the human fungal pathogen Candida albicans. C. albicans strains with mutant yak1 alleles showed defects in the yeast-to-hypha transition and in maintaining hyphal growth. They also could not form biofilms. Despite their in vitro filamentation defect, C. albicans yak1Δ/yak1Δ mutants remained virulent in animal models of systemic and oropharyngeal candidiasis. Transcriptional profiling showed that Yak1 was necessary for the up-regulation of only a subset of hypha-induced genes. Although downstream targets of the Tec1 and Bcr1 transcription factors were down-regulated in the yak1Δ/yak1Δ mutant, TEC1 and BCR1 were not. Furthermore, 63% of Yak1-dependent, hypha-specific genes have been reported to be negatively regulated by the transcriptional repressor Tup1 and inactivation of TUP1 in the yak1Δ/yak1Δ mutant restored filamentation, suggesting that Yak1 may function upstream of Tup1 in governing hyphal emergence and maintenance.

scholarly journals pH-Dependant Antifungal Activity of Valproic Acid against the Human Fungal Pathogen Candida albicans

2017 ◽  
Vol 8 ◽  
Author(s):  
Julien Chaillot ◽  
Faiza Tebbji ◽  
Carlos García ◽  
Hugo Wurtele ◽  
René Pelletier ◽  
...  
Keyword(s):  
Valproic Acid ◽  
Candida Albicans ◽  
Antifungal Activity ◽  
Fungal Pathogen ◽  
Human Fungal Pathogen

scholarly journals Pmt-Mediated O Mannosylation Stabilizes an Essential Component of the Secretory Apparatus, Sec20p, in Candida albicans

2004 ◽  
Vol 3 (5) ◽  
pp. 1164-1168 ◽  
Author(s):  
Yvonne Weber ◽  
Stephan K.-H. Prill ◽  
Joachim F. Ernst
Keyword(s):  
Endoplasmic Reticulum ◽  
Candida Albicans ◽  
Fungal Pathogen ◽  
Wild Type ◽  
Rapid Degradation ◽  
Vesicle Traffic ◽  
Human Fungal Pathogen ◽  
Low Levels ◽  
Lumenal Domain ◽  
Secretory Apparatus

ABSTRACT Sec20p is an essential endoplasmic reticulum (ER) membrane protein in yeasts, functioning as a tSNARE component in retrograde vesicle traffic. We show that Sec20p in the human fungal pathogen Candida albicans is extensively O mannosylated by protein mannosyltransferases (Pmt proteins). Surprisingly, Sec20p occurs at wild-type levels in a pmt6 mutant but at very low levels in pmt1 and pmt4 mutants and also after replacement of specific Ser/Thr residues in the lumenal domain of Sec20p. Pulse-chase experiments revealed rapid degradation of unmodified Sec20p (38.6 kDa) following its biosynthesis, while the stable O-glycosylated form (50 kDa) was not formed in a pmt1 mutant. These results suggest a novel function of O mannosylation in eukaryotes, in that modification by specific Pmt proteins will prevent degradation of ER-resident membrane proteins via ER-associated degradation or a proteasome-independent pathway.

scholarly journals Epigenetic dynamics of centromeres and neocentromeres in Cryptococcus deuterogattii

PLoS Genetics ◽  
2021 ◽  
Vol 17 (8) ◽  
pp. e1009743
Author(s):  
Klaas Schotanus ◽  
Vikas Yadav ◽  
Joseph Heitman
Keyword(s):  
Dna Methylation ◽  
Transposable Element ◽  
Fungal Pathogen ◽  
Fusion Partner ◽  
Epigenetic Memory ◽  
Chromosome Fusion ◽  
Human Fungal Pathogen ◽  
Chromosome Fusions ◽  
The Impact ◽  
Active Centromere

Deletion of native centromeres in the human fungal pathogen Cryptococcus deuterogattii leads to neocentromere formation. Native centromeres span truncated transposable elements, while neocentromeres do not and instead span actively expressed genes. To explore the epigenetic organization of neocentromeres, we analyzed the distribution of the heterochromatic histone modification H3K9me2, 5mC DNA methylation and the euchromatin mark H3K4me2. Native centromeres are enriched for both H3K9me2 and 5mC DNA methylation marks and are devoid of H3K4me2, while neocentromeres do not exhibit any of these features. Neocentromeres in cen10Δ mutants are unstable and chromosome-chromosome fusions occur. After chromosome fusion, the neocentromere is inactivated and the native centromere of the chromosome fusion partner remains as the sole, active centromere. In the present study, the active centromere of a fused chromosome was deleted to investigate if epigenetic memory promoted the re-activation of the inactive neocentromere. Our results show that the inactive neocentromere is not re-activated and instead a novel neocentromere forms directly adjacent to the deleted centromere of the fused chromosome. To study the impact of transcription on centromere stability, the actively expressed URA5 gene was introduced into the CENP-A bound regions of a native centromere. The introduction of the URA5 gene led to a loss of CENP-A from the native centromere, and a neocentromere formed adjacent to the native centromere location. Remarkably, the inactive, native centromere remained enriched for heterochromatin, yet the integrated gene was expressed and devoid of H3K9me2. A cumulative analysis of multiple CENP-A distribution profiles revealed centromere drift in C. deuterogattii, a previously unreported phenomenon in fungi. The CENP-A-binding shifted within the ORF-free regions and showed a possible association with a truncated transposable element. Taken together, our findings reveal that neocentromeres in C. deuterogattii are highly unstable and are not marked with an epigenetic memory, distinguishing them from native centromeres.

scholarly journals mSphere of Influence: the Power of Yeast Genetics Still Going Strong!

mSphere ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Felipe H. Santiago-Tirado
Keyword(s):  
Genetic Analysis ◽  
Fungal Pathogen ◽  
Cell Biology ◽  
Genetic Manipulation ◽  
Chemical Genetics ◽  
Yeast Genetics ◽  
Content Type ◽  
Human Fungal Pathogen ◽  
Link Type ◽  
Fungal Meningitis

ABSTRACT Felipe Santiago-Tirado studies the cell biology of cryptococcal infections. In this mSphere of Influence article, he reflects on how the papers “Systematic Genetic Analysis of Virulence in the Human Fungal Pathogen Cryptococcus neoformans” (https://doi.org/10.1016/j.cell.2008.07.046) and “Unraveling the Biology of a Fungal Meningitis Pathogen Using Chemical Genetics” (https://doi.org/10.1016/j.cell.2014.10.044) by the Noble and Madhani groups influenced his thinking by showcasing the various modern applications of yeast genetics in an organism where genetic manipulation was difficult.

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