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Query: UNIPROT:Q02556 (DNA-binding domain)
 6,431 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The niiA (nitrite reductase) and niaD (nitrate reductase) genes of Aspergillus nidulans are subject to both induction by nitrate and repression by ammonium or glutamine. The intergenic region between these genes functions as a bidirectional promoter. In this region, nucleosomes are positioned under nonexpression conditions. On nitrate induction under derepressing conditions, total loss of positioning occurs. This is independent of transcription and of the NirA-specific transcription factor but absolutely dependent on the wide-domain GATA-binding AreA factor. We show here that a 3-amino-acid deletion in the basic carboxy-terminal sequence of the DNA-binding domain results in a protein with paradoxical properties. Its weak DNA binding is consistent with its loss-of-function phenotype on most nitrogen sources. However, it results in constitutive expression and superinducibility of niiA and niaD. Nucleosome loss of positioning is also constitutive. The mutation partially suppresses null mutations in the transcription factor NirA. AreA binds NirA in vitro, and the mutation does not affect this interaction. The in vivo methylation pattern of the promoter is drastically altered, suggesting the recruitment of one or more unknown transcription factors and/or a local distortion on the DNA double helix.
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PMID:A paradoxical mutant GATA factor. 1507 69

The UV and visible resonance Raman spectra are reported for CooA from Rhodospirillum rubrum, which is a transcriptional regulator activated by growth in a CO atmosphere. CO binding to heme in its sensor domain causes rearrangement of its DNA-binding domain, allowing binding of DNA with a specific sequence. The sensor and DNA-binding domains are linked by a hinge region that follows a long C-helix. UV resonance Raman bands arising from Trp-110 in the C-helix revealed local movement around Trp-110 upon CO binding. The indole side chain of Trp-110, which is exposed to solvent in the CO-free ferrous state, becomes buried in the CO-bound state with a slight change in its orientation but maintains a hydrogen bond with a water molecule at the indole nitrogen. This is the first experimental data supporting a previously proposed model involving displacement of the C-helix and heme sliding. The UV resonance Raman spectra for the CooA-DNA complex indicated that binding of DNA to CooA induces a further displacement of the C-helix in the same direction during transition to the complete active conformation. The Fe-CO and C-O stretching bands showed frequency shifts upon DNA binding, but the Fe-His stretching band did not. Moreover, CO-geminate recombination was more efficient in the DNA-bound state. These results suggest that the C-helix displacement in the DNA-bound form causes the CO binding pocket to narrow and become more negative.
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PMID:Evidence for displacements of the C-helix by CO ligation and DNA binding to CooA revealed by UV resonance Raman spectroscopy. 1643 68

The Aspergillus nidulans xprG gene is involved in the regulation of extracellular proteases. A plasmid which complemented the xprG2 mutation was shown to carry the phoG gene, reported to encode an acid phosphatase. Two phoGDelta mutants were constructed and were identical in phenotype to an xprG2 mutant. Null mutants were unable to use protein as a carbon or nitrogen source, have lost a repressible acid phosphatase and have pale conidial color. XprG shows similarity to the Ndt80 transcriptional activator, which regulates the expression of genes during meiosis in Saccharomyces cerevisiae. The xprG1 gain-of-function mutant contains a missense mutation in the region encoding the putative DNA-binding domain. The response to carbon, nitrogen, sulfur, and phosphate limitation is altered in xprG(-) mutants suggesting that XprG is involved in a general response to starvation. Ndt80 may also be involved in sensing nutritional status and control of commitment to meiosis in S. cerevisiae.
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PMID:The Aspergillus nidulans xprG (phoG) gene encodes a putative transcriptional activator involved in the response to nutrient limitation. 1646 24

The heterocyst is a specialized cell for nitrogen fixation in the filamentous cyanobacteria, and its development is triggered by limitation of combined nitrogen in the medium. During heterocyst development, patterns of gene expression change dramatically. We identified seven genes encoding transcriptional regulators that were upregulated by nitrogen deprivation in Anabaena PCC 7120, using an Anabaena oligonucleotide microarray. Among them, the nrrA gene, which encodes a response regulator of the OmpR family with a DNA-binding domain, has shown the most prominent induction after nitrogen deprivation. Expression of nrrA increased all through the filaments within 3 h of nitrogen deprivation and became higher in proheterocysts than in vegetative cells after 12 h. Sequence analysis of the promoter region of nrrA indicated that the induction of nrrA depended on NtcA, which is the global nitrogen regulator in cyanobacteria. In the nrrA deletion mutant, heterocyst development was delayed and the induction of hetR, which is the master gene in regulation of heterocyst development, was diminished up to 24 h nitrogen deprivation. It is concluded that nrrA facilitates heterocyst development.
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PMID:NrrA, a nitrogen-responsive response regulator facilitates heterocyst development in the cyanobacterium Anabaena sp. strain PCC 7120. 1655 76

A homolog of the major nitrogen regulatory genes areA from Aspergillus nidulans and nit-2 from Neurospora crassa was isolated from the zoophilic dermatophyte, Microsporum canis. This gene, dnr1, encodes a polypeptide of 761 amino acid residues containing a single zinc-finger DNA-binding domain, which is almost identical in amino acid sequence to the zinc-finger domains of AREA and NIT-2. The functional equivalence of dnr1 to areA was demonstrated by complementation of an areA loss-of-function mutant of A. nidulans with dnr1 cDNA. To further characterize this gene, dnr1 was disrupted by gene replacement based on homologous recombination. Of 100 transformants analyzed, two showed the results expected for replacement of dnr1. The growth properties of the two dnr1(-) mutant strains on various nitrogen sources were examined. Unlike the A. nidulansareA(-) mutant, these dnr1(-) mutants showed significantly reduced growth on ammonia, a preferred nitrogen source for fungi. These mutant strains were also able to utilize various amino acids for growth. In comparison with wild-type M. canis, the two dnr1(-) mutants showed reduced growth on medium containing keratin as the sole nitrogen source. This is the first report describing successful production of targeted gene-disrupted mutants by homologous recombination and their phenotypic analysis in dermatophytes.
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PMID:Isolation, characterization, and disruption of dnr1, the areA/nit-2-like nitrogen regulatory gene of the zoophilic dermatophyte, Microsporum canis. 1670 4

APSES transcription factors are well-known regulators of fungal cellular development and differentiation. To study the function of an APSES protein in the fungus Wangiella dermatitidis, a conidiogenous and polymorphic agent of human phaeohyphomycosis with yeast predominance, the APSES transcription factor gene WdSTUA was cloned, sequenced, disrupted, and overexpressed. Analysis showed that its derived protein was most similar to the APSES proteins of other conidiogenous molds and had its APSES DNA-binding domain located in the amino-terminal half. Deletion of WdSTUA in W. dermatitidis induced convoluted instead of normal smooth colony surface growth on the rich yeast maintenance agar medium yeast extract-peptone-dextrose agar (YPDA) at 37 degrees C. Additionally, deletion of WdSTUA repressed aerial hyphal growth, conidiation, and invasive hyphal growth on the nitrogen-poor, hypha-inducing agar medium potato dextrose agar (PDA) at 25 degrees C. Ectopic overexpression of WdSTUA repressed the convoluted colony surface growth on YPDA at 37 degrees C, and also strongly repressed hyphal growth on PDA at 25 degrees C and 37 degrees C. These new results provide additional insights into the diverse roles played by APSES factors in fungi. They also suggest that the transcription factor encoded by WdSTUA is both a positive and negative morphotype regulator in W. dermatitidis and possibly other of the numerous human pathogenic, conidiogenous fungi capable of yeast growth.
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PMID:WdStuAp, an APSES transcription factor, is a regulator of yeast-hyphal transitions in Wangiella (Exophiala) dermatitidis. 1769 95

The NifA protein is the central regulator of the nitrogen fixation genes. It activates transcription of nif genes by an alternative holoenzyme form of RNA polymerase containing the sigma(54) factor. The NifA protein from Klebsiella pneumoniae consists of the N-terminal domain of unknown function, the central catalytic domain with ATPase activity and the C-terminal DNA-binding domain. The Kp NifA protein is sensitive to temperature, while the Enterobacter cloacae NifA protein is less sensitive to temperature than Kp NifA. Our results show that the N-terminal domain of NifA plays the decisive role in the temperature sensitivity of the protein.
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PMID:The N-terminal domain of NifA determines the temperature sensitivity of NifA in Klebsiella pneumoniae and Enterobacter cloacae. 1876 10

The Aspergillus nidulans transcription factor AreA is a key regulator of nitrogen metabolic gene expression. AreA contains a C-terminal GATA zinc finger DNA-binding domain and activates expression of genes necessary for nitrogen acquisition. Previous studies identified AreB as a potential negative regulator of nitrogen catabolism showing similarity with Penicillium chrysogenum NreB and Neurospora crassa ASD4. The areB gene encodes multiple products containing an N-terminal GATA zinc finger and a leucine zipper motif. We deleted the areB gene and now show that AreB negatively regulates AreA-dependent nitrogen catabolic gene expression under nitrogen-limiting or nitrogen-starvation conditions. AreB also acts pleiotropically, with functions in growth, conidial germination and asexual development, though not in sexual development. AreB overexpression results in severe growth inhibition, aberrant cell morphology and reduced AreA-dependent gene expression. Deletion of either the DNA-binding domain or the leucine zipper domain results in loss of both nitrogen and developmental phenotypes.
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PMID:Deletion and overexpression of the Aspergillus nidulans GATA factor AreB reveals unexpected pleiotropy. 1962 61

2-oxogluatarate (2-OG), a metabolite of the highly conserved Krebs cycle, not only plays a critical role in metabolism, but also constitutes a signaling molecule in a variety of organisms ranging from bacteria to plants and animals. In cyanobacteria, the accumulation of 2-OG constitutes the signal of nitrogen starvation and NtcA, a global transcription factor, has been proposed as a putative receptor for 2-OG. Here we present three crystal structures of NtcA from the cyanobacterium Anabaena: the apoform, and two ligand-bound forms in complex with either 2-OG or its analogue 2,2-difluoropentanedioic acid. All structures assemble as homodimers, with each subunit composed of an N-terminal effector-binding domain and a C-terminal DNA-binding domain connected by a long helix (C-helix). The 2-OG binds to the effector-binding domain at a pocket similar to that used by cAMP in catabolite activator protein, but with a different pattern. Comparative structural analysis reveals a putative signal transmission route upon 2-OG binding. A tighter coiled-coil conformation of the two C-helices induced by 2-OG is crucial to maintain the proper distance between the two F-helices for DNA recognition. Whereas catabolite activator protein adopts a transition from off-to-on state upon cAMP binding, our structural analysis explains well why NtcA can bind to DNA even in its apoform, and how 2-OG just enhances the DNA-binding activity of NtcA. These findings provided the structural insights into the function of a global transcription factor regulated by 2-OG, a metabolite standing at a crossroad between carbon and nitrogen metabolisms.
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PMID:Structural basis for the allosteric control of the global transcription factor NtcA by the nitrogen starvation signal 2-oxoglutarate. 2061 47

The transcriptional activation response relies on a repertoire of transcriptional activators, which decipher regulatory information through their specific binding to cognate sequences, and their capacity to selectively recruit the components that constitute a given transcriptional complex. We have addressed the possibility of achieving novel transcriptional responses by the construction of a new transcriptional regulator--the Hap2-3-5-Gln3 hybrid modulator--harbouring the HAP complex polypeptides that constitute the DNA-binding domain (Hap2-3-5) and the Gln3 activation domain, which usually act in an uncombined fashion. The results presented in this paper show that transcriptional activation of GDH1 and ASN1 under repressive nitrogen conditions is achieved through the action of the novel Hap2-3-5-Gln3 transcriptional regulator. We propose that the combination of the Hap DNA-binding and Gln3 activation domains results in a hybrid modulator that elicits a novel transcriptional response not evoked when these modulators act independently.
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PMID:Hap2-3-5-Gln3 determine transcriptional activation of GDH1 and ASN1 under repressive nitrogen conditions in the yeast Saccharomyces cerevisiae. 2105 84


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