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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

D55Q-T83A and D55Q-G94S, two pseudorevertants of the D55Q mutant OmpR, an Escherichia coli transcriptional activator, were isolated previously by R. Brissette, K. Tsung, and M. Inouye (J. Bacteriol. 173:3749-3755, 1991). These pseudorevertant OmpR proteins were purified and examined for their function as transcriptional activators in a cell-free system with an ompF DNA fragment. These proteins were transcriptionally active, even after acid treatment, whereas the wild-type OmpR was completely inactive after the same treatment. Phosphorylation of acid-treated wild-type OmpR with an EnvZ11 membrane fraction and ATP restored transcriptional activity, whereas the activities of the mutant OmpR proteins did not change after phosphorylation.
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PMID:Two transcriptionally active OmpR mutants that do not require phosphorylation by EnvZ in an Escherichia coli cell-free system. 132 61

The protein kinase GCN2 stimulates expression of the yeast transcriptional activator GCN4 at the translational level by phosphorylating the alpha subunit of translation initiation factor 2 (eIF-2 alpha) in amino acid-starved cells. Phosphorylation of eIF-2 alpha reduces its activity, allowing ribosomes to bypass short open reading frames present in the GCN4 mRNA leader and initiate translation at the GCN4 start codon. We describe here 17 dominant GCN2 mutations that lead to derepression of GCN4 expression in the absence of amino acid starvation. Seven of these GCN2c alleles map in the protein kinase moiety, and two in this group alter the presumed ATP-binding domain, suggesting that ATP binding is a regulated aspect of GCN2 function. Six GCN2c alleles map in a region related to histidyl-tRNA synthetases, and two in this group alter a sequence motif conserved among class II aminoacyl-tRNA synthetases that directly interacts with the acceptor stem of tRNA. These results support the idea that GCN2 kinase function is activated under starvation conditions by binding uncharged tRNA to the domain related to histidyl-tRNA synthetase. The remaining GCN2c alleles map at the extreme C terminus, a domain required for ribosome association of the protein. Representative mutations in each domain were shown to depend on the phosphorylation site in eIF-2 alpha for their effects on GCN4 expression and to increase the level of eIF-2 alpha phosphorylation in the absence of amino acid starvation. Synthetic GCN2c double mutations show greater derepression of GCN4 expression than the parental single mutations, and they have a slow-growth phenotype that we attribute to inhibition of general translation initiation. The phenotypes of the GCN2c alleles are dependent on GCN1 and GCN3, indicating that these two positive regulators of GCN4 expression mediate the inhibitory effects on translation initiation associated with activation of the yeast eIF-2 alpha kinase GCN2.
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PMID:Mutations activating the yeast eIF-2 alpha kinase GCN2: isolation of alleles altering the domain related to histidyl-tRNA synthetases. 144 7

Transcription of a eukaryotic structural gene by RNA polymerase II requires the ordered assembly of general transcription factors on the promoter to form a pre-initiation complex. Here we analyze affinity-purified complexes at various stages of assembly to determine the mechanism of action of an acidic transcriptional activator. We show that the activator can function in the absence of ATP and stimulates transcription by increasing the number of functional preinitiation complexes. The activator effects this increase by recruiting the general transcription factor TFIIB to the promoter. Using protein affinity chromatography we demonstrate a specific interaction between an acidic activating region and TFIIB. Based on these combined results, we propose that TFIIB is a direct target of an acidic activator.
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PMID:Mechanism of action of an acidic transcriptional activator in vitro. 200 92

We show that MalT, the transcriptional activator of the Escherichia coli maltose regulon, specifically binds ATP and dATP with a high affinity (Kd = 0.4 microM) and exhibits a weak ATPase activity. Using an abortive initiation assay, we further show that activation of open complex formation by MalT depends on the presence of ATP in addition to that of maltotriose, the inducer of the maltose system. Similar experiments in which ATP was replaced by ADP or AMP-PNP, a non-hydrolysable analogue of ATP, demonstrate that this reaction does not require ATP hydrolysis. As revealed by DNase I footprinting, both ATP and maltotriose are required for the binding of the MalT protein to the mal promoter DNA.
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PMID:MalT, the regulatory protein of the Escherichia coli maltose system, is an ATP-dependent transcriptional activator. 252 84

Escherichia coli lon mutants lack a major ATP-dependent protease, are sensitive to UV light and methylmethane sulfonate (MMS), and overproduce capsular polysaccharide. Evidence is presented that an activity (Alp), cloned on a multicopy plasmid, can suppress the phenotypes of lon mutants. The sensitivity to UV and MMS is a reflection of the stabilization of the cell division inhibitor SulA, while the capsule overproduction arises through the stabilization of a transcriptional activator of capsule biosynthetic genes, RcsA. Multicopy alp (pAlp) suppressed capsule formation in delta lon cells, and delta lon cells containing the pAlp plasmid were resistant to MMS treatment. The MMS resistance of delta lon pAlp+ cells correlates with an increase in the degradation of SulA to that found in lon+ cells. Lon-directed degradation of SulA was energy dependent, as was the increase in degradation of SulA in delta lon pAlp+ cells. alp maps close to pheA, at 57 min on the E. coli chromosome. Although pAlp can substitute for Lon, cells lacking alp activity did not have the phenotype on a lon mutant. This study demonstrates that at least one activity, when overproduced in the cell, can substitute for Lon protease.
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PMID:Alp, a suppressor of lon protease mutants in Escherichia coli. 265 52

The GCN2 protein of Saccharomyces cerevisiae stimulates the expression of amino acid biosynthetic genes under conditions of amino acid starvation by derepressing GCN4, a transcriptional activator of these genes. GCN2 contains sequences homologous to the catalytic domain of protein kinases. We show here that substitution of a highly conserved lysine in the presumed ATP-binding site of this domain impairs the derepression of histidine biosynthetic genes under GCN4 control. This result supports the idea that protein kinase activity is required for GCN2 positive regulatory function. Determination of the nucleotide sequence of the entire GCN2 complementation unit, and measurement of the molecular weight of GCN2 protein expressed in vivo, indicate that GCN2 is a Mr approximately 180,000 protein and contains a Mr approximately 60,000 segment homologous to histidyl-tRNA synthetases (HisRSs) juxtaposed to the protein kinase domain. Several two-codon insertion mutations in the HisRS-related coding sequences inactivate GCN2 regulatory function. Based on these results, we propose that the GCN2 HisRS domain responds to the presence of uncharged tRNA by activating the adjacent protein kinase moiety, thus providing a means of coupling GCN2-mediated derepression of GCN4 expression to the availability of amino acids.
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PMID:Juxtaposition of domains homologous to protein kinases and histidyl-tRNA synthetases in GCN2 protein suggests a mechanism for coupling GCN4 expression to amino acid availability. 266 Jan 41

PhoB protein is the transcriptional activator for genes in the phosphate regulon of Escherichia coli, such as phoA and pstS, that are induced by phosphate deprivation. PhoR protein activates PhoB when phosphate is limiting and inactivates it when phosphate is in excess. We constructed a plasmid with a mutant phoR gene (phoR1084), which encoded a PhoR protein (PhoR1084) lacking the amino-terminal hydrophobic region of the intact protein. The cells carrying the plasmid overproduced PhoR1084, which was recovered in the soluble fraction of the cell lysate. We purified the Phor1084 protein and showed that it was autophosphorylated in the presence of ATP, and the phosphate group on the protein was rapidly transferred to PhoB. The phosphorylation of PhoB protein occurred concurrently with the acquisition of the ability to activate transcription from the pstS promoter. On the basis of these findings, we propose that phosphorylated PhoB protein activates transcription from the promoters of the phosphate regulon, and that the role of PhoR is to catalyze the formation and breakdown of phosphorylated PhoB in response to phosphate concentrations in the medium.
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PMID:Signal transduction in the phosphate regulon of Escherichia coli involves phosphotransfer between PhoR and PhoB proteins. 269 38

From nucleotide sequencing analyses, the A. caulinodans nifA gene seems to be under dual control by the Ntr (in response to available N) and Fnr (in response to available O2) transcriptional activation/repression systems. Because it fixes N2 in two contexts, the Ntr system might regulate A. caulinodans nif gene expression ex planta, while the Fnr system might similarly regulate in planta. As nifA upstream-activating elements, we have identified: (i) a gpNifA binding site allowing autogenous nifA regulation, (ii) an Ntr-dependent transcription start, presumably the target of gpNifA activation, and (iii) an "anaerobox" tetradecameric nucleotide sequence that is precisely conserved among O2 regulated enteric bacterial genes controlled by the gpFnr transcriptional activator. Because it is precisely positioned upstream of enteric bacterial transcriptional starts, the "anaerobox" sequence may constitute the gpFnr DNA binding site. If so, then a second, Ntr-independent nifA transcription start may exist. We have also deduced the A. caulinodans nifA open reading frame and have compared the gene product (gpNifA) with those of other N2-fixing organisms. These proteins exhibit strongly conserved motifs: (i) sites conserved among ATP-binding proteins, (ii) an interdomain linker region, and (iii) a C-terminal alpha-helix-turn-alpha-helix DNA binding site.
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PMID:The Azorhizobium caulinodans nifA gene: identification of upstream-activating sequences including a new element, the 'anaerobox'. 318 46

In Saccharomyces cerevisiae, 3-amino-1,2,4-triazole (aminotriazole) competitively inhibits the activity of imidazoleglycerolphosphate dehydratase, the product of the HIS3 gene. Wild-type strains are able to grow in the presence of 10 mM aminotriazole because they induce the level of imidazoleglycerolphosphate dehydratase. However, strains containing gcn4 mutations are unable to grow in medium containing aminotriazole because they lack the GCN4 transcriptional activator protein necessary for the coordinate induction of HIS3 and other amino acid biosynthetic genes. Here, we isolated a new gene, designated ATR1, which when present in multiple copies per cell allowed gcn4 mutant strains to grow in the presence of aminotriazole. In wild-type strains, multiple copies of ATR1 permitted growth at extremely high concentrations of aminotriazole (80 mM), whereas a chromosomal deletion of ATR1 caused growth inhibition at very low concentrations (5 mM). When radioactive aminotriazole was added exogenously, cells with multiple copies of ATR1 accumulated less aminotriazole than wild-type cells, whereas cells with the atr1 deletion mutation retained more aminotriazole. Unlike the mammalian mdr or yeast PDR genes that confer resistance to many drugs, ATR1 appears to confer resistance only to aminotriazole. Genetic analysis, mRNA mapping, and DNA sequencing revealed that (i) the primary translation product of ATR1 contains 547 amino acids, (ii) ATR1 transcription is induced by aminotriazole, and (iii) the ATR1 promoter region contains a binding site for the GCN4 activator protein. The deduced amino acid sequence suggests that ATR1 protein is very hydrophobic with many membrane-spanning regions, has several potential glycosylation sites, and may contain an ATP-binding site. We suggest that ATR1 encodes a membrane-associated component of the machinery responsible for pumping aminotriazole (and possibly other toxic compounds) out of the cell.
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PMID:ATR1, a Saccharomyces cerevisiae gene encoding a transmembrane protein required for aminotriazole resistance. 328 Sep 70

Expression of the Escherichia coli maltose regulon is controlled by MalT, a transcriptional activator (Mr = 102,288) encoded by the malT gene. Activation of transcription depends on the presence of the inducer, maltotriose. Using an in vitro transcription/translation assay to monitor the protein, we have purified MalT in native form from MalT-overproducing bacteria. The purified protein is able to promote transcription from different MalT-controlled promoters in well-defined in vitro systems. Maltotriose and the MalT protein suffice to stimulate initiation of transcription at malPp by the E. coli RNA polymerase holoenzyme. In contrast, both MalT protein and cAMP receptor protein are required with their respective effectors, maltotriose and cyclic AMP, for activation of malEp. These data are in agreement with in vivo observations. In addition, we present evidence that MalT is an ATP-binding protein, a result suggesting that ATP may play a role in transcription initiation.
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PMID:Purification and properties of the MalT protein, the transcription activator of the Escherichia coli maltose regulon. 330 11


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