The GATA factors AREA and AREB together with the co-repressor NMRA, negatively regulate arginine catabolism in Aspergillus nidulans in response to nitrogen and carbon source (original) (raw)
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FEMS Microbiology Letters
In Aspergillus nidulans, nitrogen and carbon metabolism are under the control of wide-domain regulatory systems, including nitrogen metabolite repression, carbon catabolite repression and the nutrient starvation response. Transcriptomic analysis of the wild type strain grown under different combinations of carbon and nitrogen regimes was performed, to identify differentially regulated genes. Carbon metabolism predominates as the most important regulatory signal but for many genes, both carbon and nitrogen metabolisms coordinate regulation. To identify mechanisms coordinating nitrogen and carbon metabolism, we tested the role of AreB, previously identified as a regulator of genes involved in nitrogen metabolism. Deletion of areB has significant phenotypic effects on the utilization of specific carbon sources, confirming its role in the regulation of carbon metabolism. AreB was shown to regulate the expression of areA, tamA, creA, xprG and cpcA regulatory genes suggesting areB has a range of indirect, regulatory effects. Different isoforms of AreB are produced as a result of differential splicing and use of two promoters which are differentially regulated by carbon and nitrogen conditions. These isoforms are likely to be functionally distinct and thus contributing to the modulation of AreB activity.
Fungal Genetics and Biology, 2003
The arginine catabolism gene otaA encoding ornithine transaminase (OTAse) is specifically induced by arginine and is under the control of the broad-domain carbon and nitrogen repression systems. Arginine induction is mediated by a product of arcA gene coding for Zn 2 C 6 activator. We have identified a region responsible for arginine induction in the otaA promoter (AnUAS arg ). Deletions within this region result in non-inducibility of OTAse by arginine, whether in an arcA þ strain or in the presence of the arcA d 47 gain of function allele. AnUAS arg is very similar to the Saccharomyces cerevisiae UAS arg , a sequence bound by the Zn 2 C 6 activator (ArgRIIp), acting in a complex with two MADS-box proteins (McmIp and ArgRIp).We demonstrate here that two CREA in vitro binding sites in the otaA promoter are functional in vivo. CREA is directly involved in carbon repression of the otaA gene and it also reduces its basal level of expression. Although AREA binds to the otaA promoter in vitro, it probably does not participate in nitrogen metabolite repression of the gene in vivo. We show here that another putative negatively acting GATA factor AREB participates directly or indirectly in otaA nitrogen repression. We also demonstrate that the high levels of OTAse activity are an important factor in the suppression of proline auxotrophic mutations. This suppression can be achieved neither by growing of the proline auxotroph under carbon/nitrogen derepressing conditions nor by introducing of a creA d mutation.
Nitrogen metabolite repression in Aspergillus nidulans
MGG Molecular & General Genetics, 1973
In Aspergillus nidulans, mutations, designated areA r, can result in the inability to utilise a wide variety of nitrogen sources including amino acids, purines, amides, nitrate, and nitrite, whilst not affecting growth on i ammonium. Other allelic area mutations, designated area d, lead to derepression of one or more activities which are ammonium repressible in wild type (areA+) strains, whilst not affecting their inducibility. Various area mutations exhibit a wide variety of phenotypes: area r alleles can be temperature sensitive on some nitrogen sources while not on others, and different alleles can be temperature sensitive for utilisation of different nitrogen sources, area d alleles can be derepressed for one ammonium-repressible activity, be normally repressible for another, and lead to abnormally low levels for a third. Once again each area d allele has its own highly specific phenotype. The inability of area r strains to utilise most nitrogen sources is paralleled by low activities of certain ammonium-repressible enzymes, area r mutations appear to be epistatic to some but not all regulatory mutations leading to constitutive synthesis of inducible enzymes and also epistatic to gdhA mutations which lead both to loss of ~NADP-linked glutamate dehydrogenase and to derepression of ammonium-repressible activities.
Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression, 1998
. The gene encoding the positive-acting regulator of nitrogen metabolite repression AREA has been cloned and characterised from the industrially important filamentous fungus Aspergillus niger. The deduced amino acid sequence has an overall level of identity with its homologues from other fungal species which varies between 32 and 72%. This gene Ž . r areA complements the A. nidulans areA -18 loss-of-function mutation. Sequences upstream of the structural gene nig contain several putative GATA-type zinc finger protein-binding motifs. Northern analysis indicates the synthesis of multiple transcripts, the major species being approximately 2.95 kb and 3.1 kb. Maximal expression of areA is observed under nig conditions of nitrogen starvation and is mainly due to an increase in the level of the shorter transcript. q 1998 Elsevier Science B.V. Ž .
arcA, the regulatory gene for the arginine catabolic pathway in Aspergillus nidulans
Molecular Genetics and Genomics, 2001
We have cloned and analysed the arcA gene which encodes a transcriptional activator necessary for the high-level expression of two genes for enzymes of the arginine catabolic pathway in Aspergillus nidulans: agaA (for arginase) and otaA (for ornithine transaminase, OTAse). Here we present complete genomic and cDNA sequences for, and describe the pattern of expression of, the arcA gene. This gene contains one intron and encodes a polypeptide of 600 amino acids. The deduced protein belongs to the family of Zn 2 Cys 6 fungal regulatory proteins. ARCA is the ®rst known protein of this family that has glycine instead of the conserved proline at the ®fth position in the second, six-residue, loop of the Zn cluster domain. We have established that transcription of the arcA gene is not self-regulated and does not depend on arginine. Two mutations in arcA, one gain-of-function and one loss-of-function, have been sequenced and the eects of these mutations on the expression of the agaA gene at the transcriptional level are reported. Keywords arcA á Aspergillus á Arginine metabolism á Zinc binuclear cluster domain á Gene regulation
Role of Glutamine Synthetase in Nitrogen Metabolite Repression in Aspergillus nidulans
Journal of Bacteriology, 2001
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 functional glnA 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 glnA Δ 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 the glnA ...