1
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Georis I, Ronsmans A, Vierendeels F, Dubois E. Differing SAGA module requirements for NCR-sensitive gene transcription in yeast. Yeast 2024; 41:207-221. [PMID: 37357465 DOI: 10.1002/yea.3885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 04/24/2023] [Accepted: 05/25/2023] [Indexed: 06/27/2023] Open
Abstract
Nitrogen catabolite repression (NCR) is a means for yeast to adapt its transcriptome to changing nitrogen sources in its environment. In conditions of derepression (under poor nitrogen conditions, upon rapamycin treatment, or when glutamine production is inhibited), two transcriptional activators of the GATA family are recruited to NCR-sensitive promoters and activate transcription of NCR-sensitive genes. Earlier observations have involved the Spt-Ada-Gcn5 acetyltransferase (SAGA) chromatin remodeling complex in these transcriptional regulations. In this report, we provide an illustration of the varying NCR-sensitive responses and question whether differing SAGA recruitment could explain this diversity of responses.
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Affiliation(s)
| | | | | | - Evelyne Dubois
- Labiris, Brussels, Belgium
- Université Libre de Bruxelles, Brussels, Belgium
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2
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Chen Y, Zeng W, Ma W, Ma W, Zhou J. Chromatin Regulators Ahc1p and Eaf3p Positively Influence Nitrogen Metabolism in Saccharomyces cerevisiae. Front Microbiol 2022; 13:883934. [PMID: 35620110 PMCID: PMC9127870 DOI: 10.3389/fmicb.2022.883934] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/12/2022] [Indexed: 11/13/2022] Open
Abstract
There is a complex regulatory network of nitrogen metabolism in Saccharomyces cerevisiae, and many details of this regulatory network have not been revealed. This study explored the global regulation of nitrogen metabolism in S. cerevisiae from an epigenetic perspective. Comparative transcriptome analysis of S. cerevisiae S288C treated with 30 nitrogen sources identified nine chromatin regulators (CRs) that responded significantly to different nitrogen sources. Functional analysis showed that among the CRs identified, Ahc1p and Eaf3p promoted the utilization of non-preferred nitrogen sources through global regulation of nitrogen metabolism. Ahc1p regulated nitrogen metabolism through amino acid transport, nitrogen catabolism repression (NCR), and the Ssy1p-Ptr3p-Ssy5p signaling sensor system. Eaf3p regulated nitrogen metabolism via amino acid transport and NCR. The regulatory mechanisms of the effects of Ahc1p and Eaf3p on nitrogen metabolism depended on the function of their histone acetyltransferase complex ADA and NuA4. These epigenetic findings provided new insights for a deeper understanding of the nitrogen metabolism regulatory network in S. cerevisiae.
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Affiliation(s)
- Yu Chen
- Science Center for Future Foods, Jiangnan University, Wuxi, China.,Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, Wuxi, China.,Engineering Research Center of Ministry of Education on Food Synthetic Biotechnology, Jiangnan University, Wuxi, China
| | - Weizhu Zeng
- Science Center for Future Foods, Jiangnan University, Wuxi, China.,Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, Wuxi, China.,Jiangsu Province Engineering Research Center of Food Synthetic Biotechnology, Jiangnan University, Wuxi, China
| | - Wenjian Ma
- Science Center for Future Foods, Jiangnan University, Wuxi, China.,Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, Wuxi, China.,Engineering Research Center of Ministry of Education on Food Synthetic Biotechnology, Jiangnan University, Wuxi, China
| | - Wei Ma
- Science Center for Future Foods, Jiangnan University, Wuxi, China.,Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, Wuxi, China.,Engineering Research Center of Ministry of Education on Food Synthetic Biotechnology, Jiangnan University, Wuxi, China
| | - Jingwen Zhou
- Science Center for Future Foods, Jiangnan University, Wuxi, China.,Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, Wuxi, China.,Engineering Research Center of Ministry of Education on Food Synthetic Biotechnology, Jiangnan University, Wuxi, China.,Jiangsu Province Engineering Research Center of Food Synthetic Biotechnology, Jiangnan University, Wuxi, China
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3
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Mara P, Fragiadakis GS, Gkountromichos F, Alexandraki D. The pleiotropic effects of the glutamate dehydrogenase (GDH) pathway in Saccharomyces cerevisiae. Microb Cell Fact 2018; 17:170. [PMID: 30384856 PMCID: PMC6211499 DOI: 10.1186/s12934-018-1018-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 10/29/2018] [Indexed: 12/19/2022] Open
Abstract
Ammonium assimilation is linked to fundamental cellular processes that include the synthesis of non-essential amino acids like glutamate and glutamine. In Saccharomyces cerevisiae glutamate can be synthesized from α-ketoglutarate and ammonium through the action of NADP-dependent glutamate dehydrogenases Gdh1 and Gdh3. Gdh1 and Gdh3 are evolutionarily adapted isoforms and cover the anabolic role of the GDH-pathway. Here, we review the role and function of the GDH pathway in glutamate metabolism and we discuss the additional contributions of the pathway in chromatin regulation, nitrogen catabolite repression, ROS-mediated apoptosis, iron deficiency and sphingolipid-dependent actin cytoskeleton modulation in S.cerevisiae. The pleiotropic effects of GDH pathway in yeast biology highlight the importance of glutamate homeostasis in vital cellular processes and reveal new features for conserved enzymes that were primarily characterized for their metabolic capacity. These newly described features constitute insights that can be utilized for challenges regarding genetic engineering of glutamate homeostasis and maintenance of redox balances, biosynthesis of important metabolites and production of organic substrates. We also conclude that the discussed pleiotropic features intersect with basic metabolism and set a new background for further glutamate-dependent applied research of biotechnological interest.
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Affiliation(s)
- P. Mara
- Department of Chemistry, University of Crete, Voutes University Campus, 71003 Heraklion, Crete Greece
- Present Address: Woods Hole Oceanographic Institution, Woods Hole, MA 02543 USA
| | - G. S. Fragiadakis
- Institute of Molecular Biology & Biotechnology, FORTH, Nikolaou Plastira 100 GR-70013, Heraklion, Crete Greece
| | - F. Gkountromichos
- Department of Biology, University of Crete, Voutes University Campus, 71003 Heraklion, Crete Greece
- Faculty of Biology, Biocenter, Ludwig-Maximilians-University of Munich, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany
| | - D. Alexandraki
- Department of Biology, University of Crete, Voutes University Campus, 71003 Heraklion, Crete Greece
- Institute of Molecular Biology & Biotechnology, FORTH, Nikolaou Plastira 100 GR-70013, Heraklion, Crete Greece
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4
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Pérez-delos Santos FJ, Riego-Ruiz L. Gln3 is a main regulator of nitrogen assimilation in Candida glabrata. Microbiology (Reading) 2016; 162:1490-1499. [DOI: 10.1099/mic.0.000312] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Francisco J. Pérez-delos Santos
- Laboratory of Functional and Comparative Genomics, División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), A. C., San Luis Potosí, México
| | - Lina Riego-Ruiz
- Laboratory of Functional and Comparative Genomics, División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), A. C., San Luis Potosí, México
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5
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Tangsombatvichit P, Semkiv MV, Sibirny AA, Jensen LT, Ratanakhanokchai K, Soontorngun N. Zinc cluster protein Znf1, a novel transcription factor of non-fermentative metabolism in Saccharomyces cerevisiae. FEMS Yeast Res 2015; 15:fou002. [PMID: 25673751 DOI: 10.1093/femsyr/fou002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The ability to rapidly respond to nutrient changes is a fundamental requirement for cell survival. Here, we show that the zinc cluster regulator Znf1 responds to altered nutrient signals following glucose starvation through the direct control of genes involved in non-fermentative metabolism, including those belonged to the central pathways of gluconeogenesis (PCK1, FBP1 and MDH2), glyoxylate shunt (MLS1 and ICL1) and the tricarboxylic acid cycle (ACO1), which is demonstrated by Znf1-binding enrichment at these promoters during the glucose-ethanol shift. Additionally, reduced Pck1 and Fbp1 enzymatic activities correlate well with the data obtained from gene transcription analysis. Cells deleted for ZNF1 also display defective mitochondrial morphology with unclear structures of the inner membrane cristae when grown in ethanol, in agreement with the substantial reduction in the ATP content, suggesting for roles of Znf1 in maintaining mitochondrial morphology and function. Furthermore, Znf1 also plays a role in tolerance to pH and osmotic stress, especially during the oxidative metabolism. Taken together, our results clearly suggest that Znf1 is a critical transcriptional regulator for stress adaptation during non-fermentative growth with some partial overlapping targets with previously reported regulators in Saccharomyces cerevisiae.
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Affiliation(s)
- Pitchya Tangsombatvichit
- Division of Biochemical Technology, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkok 10150, Thailand
| | - Marta V Semkiv
- Institute of Cell Biology, NAS of Ukraine, Lviv 79005, Ukraine
| | - Andriy A Sibirny
- Institute of Cell Biology, NAS of Ukraine, Lviv 79005, Ukraine Department of Biotechnology and Microbiology, University of Rzeszow, Rzeszow 35-601, Poland
| | - Laran T Jensen
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Khanok Ratanakhanokchai
- Division of Biochemical Technology, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkok 10150, Thailand
| | - Nitnipa Soontorngun
- Division of Biochemical Technology, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkok 10150, Thailand
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6
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Rai R, Tate JJ, Georis I, Dubois E, Cooper TG. Constitutive and nitrogen catabolite repression-sensitive production of Gat1 isoforms. J Biol Chem 2013; 289:2918-33. [PMID: 24324255 DOI: 10.1074/jbc.m113.516740] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitrogen catabolite repression (NCR)-sensitive transcription is activated by Gln3 and Gat1. In nitrogen excess, Gln3 and Gat1 are cytoplasmic, and transcription is minimal. In poor nitrogen, Gln3 and Gat1 become nuclear and activate transcription. A long standing paradox has surrounded Gat1 production. Gat1 was first reported as an NCR-regulated activity mediating NCR-sensitive transcription in gln3 deletion strains. Upon cloning, GAT1 transcription was, as predicted, NCR-sensitive and Gln3- and Gat1-activated. In contrast, Western blots of Gat1-Myc(13) exhibited two constitutively produced species. Investigating this paradox, we demonstrate that wild type Gat1 isoforms (IsoA and IsoB) are initiated at Gat1 methionines 40, 95, and/or 102, but not at methionine 1. Their low level production is the same in rich and poor nitrogen conditions. When the Myc(13) tag is placed after Gat1 Ser-233, four N-terminal Gat1 isoforms (IsoC-F) are also initiated at methionines 40, 95, and/or 102. However, their production is highly NCR-sensitive, being greater in proline than glutamine medium. Surprisingly, all Gat1 isoforms produced in sufficient quantities to be confidently analyzed (IsoA, IsoC, and IsoD) require Gln3 and UASGATA promoter elements, both requirements typical of NCR-sensitive transcription. These data demonstrate that regulated Gat1 production is more complex than previously recognized, with wild type versus truncated Gat1 proteins failing to be regulated in parallel. This is the first reported instance of Gln3 UASGATA-dependent protein production failing to derepress in nitrogen poor conditions. A Gat1-lacZ ORF swap experiment indicated sequence(s) responsible for the nonparallel production are downstream of Gat1 leucine 61.
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Affiliation(s)
- Rajendra Rai
- From the Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee 38163 and
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7
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Epistatic relationships reveal the functional organization of yeast transcription factors. Mol Syst Biol 2011; 6:420. [PMID: 20959818 DOI: 10.1038/msb.2010.77] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 08/27/2010] [Indexed: 11/09/2022] Open
Abstract
The regulation of gene expression is, in large part, mediated by interplay between the general transcription factors (GTFs) that function to bring about the expression of many genes and site-specific DNA-binding transcription factors (STFs). Here, quantitative genetic profiling using the epistatic miniarray profile (E-MAP) approach allowed us to measure 48 391 pairwise genetic interactions, both negative (aggravating) and positive (alleviating), between and among genes encoding STFs and GTFs in Saccharomyces cerevisiae. This allowed us to both reconstruct regulatory models for specific subsets of transcription factors and identify global epistatic patterns. Overall, there was a much stronger preference for negative relative to positive genetic interactions among STFs than there was among GTFs. Negative genetic interactions, which often identify factors working in non-essential, redundant pathways, were also enriched for pairs of STFs that co-regulate similar sets of genes. Microarray analysis demonstrated that pairs of STFs that display negative genetic interactions regulate gene expression in an independent rather than coordinated manner. Collectively, these data suggest that parallel/compensating relationships between regulators, rather than linear pathways, often characterize transcriptional circuits.
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8
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O'Donnell AF, Apffel A, Gardner RG, Cyert MS. Alpha-arrestins Aly1 and Aly2 regulate intracellular trafficking in response to nutrient signaling. Mol Biol Cell 2010; 21:3552-66. [PMID: 20739461 PMCID: PMC2954120 DOI: 10.1091/mbc.e10-07-0636] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Arrestins, known regulators of endocytosis, take on novel functions in nutrient-regulated endosomal recycling. Yeast α-arrestins, Aly1 and Aly2, redistribute the Gap1 permease from endosomes to the cell surface and interact with clathrin/AP-1. Aly2 is regulated by the Npr1 kinase and acts through mechanisms distinct from Aly1. Extracellular signals regulate trafficking events to reorganize proteins at the plasma membrane (PM); however, few effectors of this regulation have been identified. β-Arrestins relay signaling cues to the trafficking machinery by controlling agonist-stimulated endocytosis of G-protein–coupled receptors. In contrast, we show that yeast α-arrestins, Aly1 and Aly2, control intracellular sorting of Gap1, the general amino acid permease, in response to nutrients. These studies are the first to demonstrate association of α-arrestins with clathrin and clathrin adaptor proteins (AP) and show that Aly1 and Aly2 interact directly with the γ-subunit of AP-1, Apl4. Aly2-dependent trafficking of Gap1 requires AP-1, which mediates endosome-to-Golgi transport, and the nutrient-regulated kinase, Npr1, which phosphorylates Aly2. During nitrogen starvation, Npr1 phosphorylation of Aly2 may stimulate Gap1 incorporation into AP-1/clathrin-coated vesicles to promote Gap1 trafficking from endosomes to the trans-Golgi network. Ultimately, increased Aly1-/Aly2-mediated recycling of Gap1 from endosomes results in higher Gap1 levels within cells and at the PM by diverting Gap away from trafficking pathways that lead to vacuolar degradation. This work defines a new role for arrestins in membrane trafficking and offers insight into how α-arrestins coordinate signaling events with protein trafficking.
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9
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Tomás-Cobos L, Viana R, Sanz P. TOR kinase pathway and 14-3-3 proteins regulate glucose-induced expression of HXT1, a yeast low-affinity glucose transporter. Yeast 2005; 22:471-9. [PMID: 15849787 DOI: 10.1002/yea.1224] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Expression of HXT1, a gene encoding a Saccharomyces cerevisiae low-affinity glucose transporter, is regulated by glucose availability, being activated in the presence of glucose and inhibited when the levels of the sugar are scarce. In this study we show that 14-3-3 proteins are involved in the regulation of the expression of HXT1 by glucose. We also demonstrate that 14-3-3 proteins, in complex with Reg1, a regulatory subunit of Glc7 protein phosphatase, interact physically with Grr1 (a component of the SCF-Grr1 ubiquitination complex), a key player in the process of HXT1 induction by glucose. In addition, we show that the TOR kinase pathway participates actively in the induction of HXT1 expression by glucose. Inhibition of the TOR kinase pathway by rapamycin treatment abolishes HXT1 glucose induction. A possible involvement of PP2A protein phosphatase complex, through the Cdc55 B-subunit, in the glucose induction of HXT1 is also discussed.
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Affiliation(s)
- Lidia Tomás-Cobos
- Instituto de Biomedicina de Valencia (CSIC), Jaime Roig 11, 46010-Valencia, Spain
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10
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Saxena D, Kannan KB, Brandriss MC. Rapamycin treatment results in GATA factor-independent hyperphosphorylation of the proline utilization pathway activator in Saccharomyces cerevisiae. EUKARYOTIC CELL 2003; 2:552-9. [PMID: 12796300 PMCID: PMC161436 DOI: 10.1128/ec.2.3.552-559.2003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Treatment of Saccharomyces cerevisiae cells with the immunosuppressive drug rapamycin results in a variety of cellular changes in response to perceived nutrient deprivation. Among other effects, rapamycin treatment results in the nuclear localization of the global nitrogen activators Gln3p and Nil1p/Gat1p, which leads to expression of nitrogen assimilation genes. The proline utilization (Put) pathway genes were shown to be among the genes induced by rapamycin. Having previously shown that the Put pathway activator Put3p is differentially phosphorylated in response to the quality of the nitrogen source, we examined the phosphorylation status of Put3p after rapamycin treatment. Treatment with rapamycin resulted in the hyperphosphorylation of Put3p, which was independent of Gln3p, Nil1p, and Ure2p. The relative contributions of global nitrogen (Gln3p and Nil1p) and pathway-specific (Put3p) activators to rapamycin-induced expression of the target gene PUT1 were also examined. We found that Nil1p and Put3p, but not Gln3p, play major roles in rapamycin-induced PUT1 expression. Our findings show that perceived nitrogen deprivation triggered by rapamycin treatment and steady-state growth in nitrogen-derepressing conditions are associated with hyperphosphorylation of Put3p and increased PUT1 expression. Rapamycin treatment and nitrogen derepression may share some, but not all, regulatory elements, since Gln3p and Nil1p do not participate identically in both processes and are not required for hyperphosphorylation. A complex relationship exists among the global and pathway-specific regulators, depending on the nature and quality of the nitrogen source.
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Affiliation(s)
- Deepti Saxena
- Department of Microbiology and Molecular Genetics, UMDNJ-New Jersey Medical School, Newark 07101-1709, USA
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11
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Albers E, Laizé V, Blomberg A, Hohmann S, Gustafsson L. Ser3p (Yer081wp) and Ser33p (Yil074cp) are phosphoglycerate dehydrogenases in Saccharomyces cerevisiae. J Biol Chem 2003; 278:10264-72. [PMID: 12525494 DOI: 10.1074/jbc.m211692200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two genes YER081W and YIL074C, renamed SER3 and SER33, respectively, which encode phosphoglycerate dehydrogenases in Saccharomyces cerevisiae were identified. These dehydrogenases catalyze the first reaction of serine and glycine biosynthesis from the glycolytic metabolite 3-phosphoglycerate. Unlike either single mutant, the ser3Delta ser33Delta double mutant lacks detectable phosphoglycerate dehydrogenase activity and is auxotrophic for serine or glycine for growth on glucose media. However, the requirement for the SER-dependent "phosphoglycerate pathway" is conditional since the "glyoxylate" route of serine/glycine biosynthesis is glucose-repressed. Thus, in cells grown on ethanol both expression and activity of all SER-encoded proteins are low, including the remaining enzymes of the phosphoglycerate pathway, Ser1p and Ser2p. Moreover the available nitrogen source regulates the expression of SER genes. However, for only SER33, and not SER3, expression was regulated in relation to the available nitrogen source in a coordinated fashion with SER1 and SER2. Based on these mRNA data together with data on enzyme activities, Ser33p is likely to be the main isoenzyme of the phosphoglycerate pathway during growth on glucose. Moreover, since phosphoglycerate dehydrogenase activity requires NAD(+) as cofactor, deletion of SER3 and SER33 markedly affected redox metabolism as shown by substrate and product analysis.
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Affiliation(s)
- Eva Albers
- Department of Molecular Biotechnology, Chalmers University of Technology, Box 462, SE-405 30 Göteborg, Sweden.
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12
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Morozov IY, Galbis-Martinez M, Jones MG, Caddick MX. Characterization of nitrogen metabolite signalling in Aspergillus via the regulated degradation of areA mRNA. Mol Microbiol 2001; 42:269-77. [PMID: 11679084 DOI: 10.1046/j.1365-2958.2001.02636.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AreA is the principal transcription factor involved in determining nitrogen utilization in Aspergillus nidulans. NH4+ and Gln are utilized preferentially but in their absence, AreA acts to facilitate the expression of genes involved in metabolizing alternative nitrogen sources. It is crucial to the function of AreA that its expression is tightly modulated by the quality and availability of nitrogen sources. One signalling mechanism involves regulated degradation of the areA transcript in response to NH4+ and Gln, which provides the first direct means of monitoring nitrogen signalling in this fungus. Here we assess the specificity of the transcript degradation response, determining that it responds qualitatively to a variety of additional nitrogen sources including Asn. Furthermore, the response to Gln and NH4+ requires the same discrete region of the areA 3'-UTR but both NH4+ and Asn need to be metabolized to Gln before they are effective as a signal. However, NH4+ signalling is independent of AreA activity, unlike Gln and Asn signalling. A mutation in the structural gene for NADP-linked glutamate dehydrogenase, gdhA, which disrupts metabolism of NH4+ to Glu, is additive with mutations in two distinct regions of areA that disrupt the previously identified signalling mechanisms. The triple mutant is both strongly derepressed and expresses very high levels of nitrate reductase activity. These data suggest nitrogen metabolism in A. nidulans is in part regulated in response to the intracellular levels of Gln via the regulated degradation of areA mRNA, but the intracellular Gln level is not the sole determinant of nitrogen metabolite repression.
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Affiliation(s)
- I Y Morozov
- Plant Science and Fungal Molecular Biology Research Group, School of Biological Sciences, Donnan Labs, The University of Liverpool, Liverpool L69 7ZD, UK
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13
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Huang HL, Brandriss MC. The regulator of the yeast proline utilization pathway is differentially phosphorylated in response to the quality of the nitrogen source. Mol Cell Biol 2000; 20:892-9. [PMID: 10629046 PMCID: PMC85206 DOI: 10.1128/mcb.20.3.892-899.2000] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The proline utilization pathway in Saccharomyces cerevisiae is regulated by the Put3p transcriptional activator in response to the presence of the inducer proline and the quality of the nitrogen source in the growth medium. Put3p is constitutively bound to the promoters of its target genes, PUT1 and PUT2, under all conditions studied but activates transcription to the maximum extent only in the absence of rich nitrogen sources and in the presence of proline (i.e., when proline serves as the sole source of nitrogen). Changes in target gene expression therefore occur through changes in the activity of the DNA-bound regulator. In this report, we demonstrate by phosphatase treatment of immunoprecipitates of extracts metabolically labeled with (32)P or (35)S that Put3p is a phosphoprotein. Examination of Put3p isolated from cells grown on a variety of nitrogen sources showed that it was differentially phosphorylated as a function of the quality of the nitrogen source: the poorer the nitrogen source, the slower the gel migration of the phosphoforms. The presence of the inducer does not detectably alter the phosphorylation profile. Activator-defective and activator-constitutive Put3p mutants have been analyzed. One activator-defective mutant appears to be phosphorylated in a pattern similar to that of the wild type, thus separating its ability to be phosphorylated from its ability to activate transcription. Three activator-constitutive mutant proteins from cells grown on an ammonia-containing medium have a phosphorylation profile similar to that of the wild-type protein in cells grown on proline. These results demonstrate a correlation between the phosphorylation status of Put3p and its ability to activate its target genes and suggest that there are two signals, proline induction and quality of nitrogen source, impinging on Put3p that act synergistically for maximum expression of the proline utilization pathway.
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Affiliation(s)
- H L Huang
- Department of Microbiology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07103, USA
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14
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ter Schure EG, van Riel NA, Verrips CT. The role of ammonia metabolism in nitrogen catabolite repression in Saccharomyces cerevisiae. FEMS Microbiol Rev 2000; 24:67-83. [PMID: 10640599 DOI: 10.1111/j.1574-6976.2000.tb00533.x] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Saccharomyces cerevisiae is able to use a wide variety of nitrogen sources for growth. Not all nitrogen sources support growth equally well. In order to select the best out of a large diversity of available nitrogen sources, the yeast has developed molecular mechanisms. These mechanisms consist of a sensing mechanism and a regulatory mechanism which includes induction of needed systems, and repression of systems that are not beneficial. The first step in use of most nitrogen sources is its uptake via more or less specific permeases. Hence the first level of regulation is encountered at this level. The next step is the degradation of the nitrogen source to useful building blocks via the nitrogen metabolic pathways. These pathways can be divided into routes that lead to the degradation of the nitrogen source to ammonia and glutamate, and routes that lead to the synthesis of nitrogen containing compounds in which glutamate and glutamine are used as nitrogen donor. Glutamine is synthesized out of ammonia and glutamate. The expression of the specific degradation routes is also regulated depending on the availability of a particular nitrogen source. Ammonia plays a central role as intermediate between degradative and biosynthetic pathways. It not only functions as a metabolite in metabolic reactions but is also involved in regulation of metabolic pathways at several levels. This review describes the central role of ammonia in nitrogen metabolism. This role is illustrated at the level of enzyme activity, translation and transcription.
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Affiliation(s)
- E G ter Schure
- Unilever Research, Laboratorium Vlaardingen, Olivier van Noortlaan 120, 3133 AT, Vlaardingen, The Netherlands.
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