Nitrogen Metabolite Repression of Metabolism and Virulence in the Human Fungal PathogenCryptococcus neoformans

ABSTRACT Glutamine synthetase (GS), EC 6.3.1.2 , is a central enzyme in the assimilation of nitrogen and the biosynthesis of glutamine. We have isolated the Aspergillus nidulans glnA gene encoding GS and have shown that glnA encodes a highly expressed but not highly regulated mRNA. Inactivation of glnA results in an absolute glutamine requirement, indicating that GS is responsible for the synthesis of this essential amino acid. Even when supplemented with high levels of glutamine, strains lacking a functionalglnA gene have an inhibited morphology, and a wide range of compounds have been shown to interfere with repair of the glutamine auxotrophy. Heterologous expression of the prokaryotic Anabaena glnA gene from the A. nidulans alcA promoter allowed full complementation of the A. nidulans glnAΔ mutation. However, the A. nidulans fluG gene, which encodes a protein with similarity to prokaryotic GS, did not replace A. nidulans glnA function when similarly expressed. Our studies with theglnAΔ mutant confirm that glutamine, and not GS, is the key effector of nitrogen metabolite repression. Additionally, ammonium and its immediate product glutamate may also act directly to signal nitrogen sufficiency.

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Negative Roles of a Novel Nitrogen Metabolite Repression-Related Gene, TAR1, in Laccase Production and Nitrate Utilization by the Basidiomycete Cryptococcus neoformans

Applied and Environmental Microbiology ◽

10.1128/aem.00708-09 ◽

2009 ◽

Vol 75 (21) ◽

pp. 6777-6782 ◽

Cited By ~ 18

Author(s):

Nan Jiang ◽

Dongguang Xiao ◽

Defa Zhang ◽

Naiyu Sun ◽

Bing Yan ◽

...

Keyword(s):

Cryptococcus Neoformans ◽

Binding Sites ◽

Promoter Region ◽

Laccase Activity ◽

Laccase Production ◽

Related Gene ◽

Putative Protein ◽

Nitrogen Metabolite Repression ◽

Negative Role ◽

Gaa Repeats

ABSTRACT The multicopper oxidase laccase is widespread in fungi and has great industrial importance. One puzzle regarding laccase production in the basidiomycetous yeast Cryptococcus neoformans is that it is inhibited by high temperature (e.g., 37°C). In this paper, we report identification of a nitrogen metabolite repression-related gene, TAR1, which is responsible for laccase repression. Disruption of TAR1 results in a significant increase in the level of LAC1 mRNA at 37°C. The putative protein Tar1 shares a moderate level of similarity with the nitrogen metabolite repressors Nmr1 and NmrA from Neurospora crassa and Aspergillus nidulans, respectively. Likewise, Tar1 has a negative role in the utilization of nitrate. Furthermore, the structure of Tar1 is unique. Tar1 lacks the long C-terminal region of Nmr1 and NmrA. It contains the canonical Rossmann fold motif, GlyXXGlyXXGly, whereas Nmr1 and NmrA have variable residues at the Gly positions. Interestingly, the promoter region of TAR1 contains three TTC/GAA repeats which are likely the heat shock factor (Hsf) binding sites, implying that Hsf has a role in laccase inhibition. TAR1 mediation of temperature-associated repression of LAC1 suggests a novel mechanism of laccase regulation and a new function for Nmr proteins. Our work may be helpful for industry in terms of promotion of laccase activity.

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Isolation and Characterization of Methylammonium-resistant Mutants of Saccharomyces cerevisiae with Relieved Nitrogen Metabolite Repression of Allantoinase, Arginase and Ornithine Transaminase Synthesis

Journal of General Microbiology ◽

10.1099/00221287-100-2-257 ◽

1977 ◽

Vol 100 (2) ◽

pp. 257-269 ◽

Cited By ~ 17

Author(s):

W. J. MIDDELHOVEN

Keyword(s):

Saccharomyces Cerevisiae ◽

Nitrogen Metabolite Repression ◽

Isolation And Characterization ◽

Ornithine Transaminase ◽

Resistant Mutants

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Mutational Analysis of AREA, a Transcriptional Activator Mediating Nitrogen Metabolite Repression in Aspergillus nidulans and a Member of the “Streetwise” GATA Family of Transcription Factors

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.62.3.586-596.1998 ◽

1998 ◽

Vol 62 (3) ◽

pp. 586-596 ◽

Cited By ~ 84

Author(s):

Richard A. Wilson ◽

Herbert N. Arst

Keyword(s):

Transcription Factor ◽

Transcription Factors ◽

Dna Binding ◽

Aspergillus Nidulans ◽

Transcriptional Activator ◽

Structural Genes ◽

Gata Factor ◽

Mutational Change ◽

Nitrogen Metabolite Repression ◽

Gata Family

SUMMARY The transcriptional activator AREA is a member of the GATA family of transcription factors and mediates nitrogen metabolite repression in the fungus Aspergillus nidulans. The nutritional versatility of A. nidulans and its amenability to classical and reverse genetic manipulations make the AREA DNA binding domain (DBD) a useful model for analyzing GATA family DBDs, particularly as structures of two AREA-DNA complexes have been determined. The 109 extant mutant forms of the AREA DBD surveyed here constitute one of the highest totals of eukaryotic transcription factor DBD mutants, are discussed in light of the roles of individual residues, and are compared to corresponding mutant sequence changes in other fungal GATA factor DBDs. Other topics include delineation of the DBD using both homology and mutational truncation, use of frameshift reversion to detect regions of tolerance to mutational change, the finding that duplication of the DBD can apparently enhance AREA function, and use of the AREA system to analyze a vertebrate GATA factor DBD. Some major points to emerge from work on the AREA DBD are (i) tolerance to sequence change (with retention of function) is surprisingly great, (ii) mutational changes in a transcription factor can have widely differing, even opposing, effects on expression of different structural genes so that monitoring expression of one or even several structural genes can be insufficient and possibly misleading, and (iii) a mutational change altering local hydrophobic packing and DNA binding target specificity can markedly influence the behavior of mutational changes elsewhere in the DBD.

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AgtA, the Dicarboxylic Amino Acid Transporter of Aspergillus nidulans, Is Concertedly Down-Regulated by Exquisite Sensitivity to Nitrogen Metabolite Repression and Ammonium-Elicited Endocytosis

Eukaryotic Cell ◽

10.1128/ec.00270-08 ◽

2009 ◽

Vol 8 (3) ◽

pp. 339-352 ◽

Cited By ~ 23

Author(s):

Angeliki Apostolaki ◽

Zoi Erpapazoglou ◽

Laura Harispe ◽

Maria Billini ◽

Panagiota Kafasla ◽

...

Keyword(s):

Amino Acid ◽

Aspergillus Nidulans ◽

Amino Acid Transporter ◽

Acid Transport ◽

Transport Activity ◽

High Affinity ◽

Nitrogen Metabolite Repression ◽

Dicarboxylic Amino Acid ◽

Specific Induction ◽

Acid Transporter

ABSTRACT We identified agtA, a gene that encodes the specific dicarboxylic amino acid transporter of Aspergillus nidulans. The deletion of the gene resulted in loss of utilization of aspartate as a nitrogen source and of aspartate uptake, while not completely abolishing glutamate utilization. Kinetic constants showed that AgtA is a high-affinity dicarboxylic amino acid transporter and are in agreement with those determined for a cognate transporter activity identified previously. The gene is extremely sensitive to nitrogen metabolite repression, depends on AreA for its expression, and is seemingly independent from specific induction. We showed that the localization of AgtA in the plasma membrane necessitates the ShrA protein and that an active process elicited by ammonium results in internalization and targeting of AgtA to the vacuole, followed by degradation. Thus, nitrogen metabolite repression and ammonium-promoted vacuolar degradation act in concert to downregulate dicarboxylic amino acid transport activity.

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