Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The enzymes of the proline utilization pathway (the products of the PUT1 and PUT2 genes) in Saccharomyces cerevisiae are coordinately regulated by proline and the PUT3 transcriptional activator. To learn more about the control of this pathway, constitutive mutations in PUT3 as well as in other regulators were sought. A scheme using a gene fusion between PUT1 (S. cerevisiae proline oxidase) and galK (Escherichia coli galactokinase) was developed to select directly for constitutive mutations affecting the PUT1 promoter. These mutations were secondarily screened for their effects in trans on the promoter of the PUT2 (delta 1-pyrroline-5-carboxylate dehydrogenase) gene by using a PUT2-lacZ (E. coli beta-galactosidase) gene fusion. Three different classes of mutations were isolated. The major class consisted of semidominant constitutive PUT3 mutations that caused PUT2-lacZ expression to vary from 2 to 22 times the uninduced level. A single dominant mutation in a new locus called PUT5 resulted in low-level constitutive expression of PUT2-lacZ; this mutation was epistatic to the recessive, noninducible put3-75 allele. Recessive constitutive mutations were isolated that had pleiotropic growth defects; it is possible that these mutations are not specific to the proline utilization pathway but may be in genes that control several pathways. Since the PUT3 gene appears to have a major role in the regulation of this pathway, a molecular analysis was undertaken. This gene was cloned by functional complementation of the put3-75 mutation. Strains carrying a complete deletion of this gene are viable, proline nonutilizing, and indistinguishable in phenotype from the original put3-75 allele. The PUT3 gene encodes a 2.8-kilobase-pair transcript that is not regulated by proline at the level of RNA accumulation. The presence of the gene on a high-copy-number plasmid did not alter the regulation of one of its target genes, PUT2-lacZ, suggesting that the PUT3 gene product is not limiting and that a titratable repressor is not involved in the regulation of this pathway.
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PMID:Isolation of constitutive mutations affecting the proline utilization pathway in Saccharomyces cerevisiae and molecular analysis of the PUT3 transcriptional activator. 268 61

Citrobacter freundii encodes an inducible chromosomal beta-lactamase. Induction requires the product of the ampR gene, which is transcribed in the opposite orientation from the ampC beta-lactamase gene. We show here that the AmpR protein acts as a transcriptional activator by binding to a DNA region immediately upstream of the ampC promoter. The DNase I footprint pattern was not affected by growth in the presence of beta-lactam inducer or by the use of extracts prepared from cells carrying the ampD2 allele leading to semiconstitutive production of beta-lactamase. It is suggested that activation of AmpR facilitates binding or open complex formation for RNA polymerase at the ampC promoter. The AmpR-binding site overlaps the ampR promoter, and beta-galactosidase activity was decreased from an ampR-lacZ transcriptional fusion when AmpR was expressed from a coresident plasmid, suggesting that ampR is autogenously controlled. The AmpR protein belongs to a family of highly homologous transcriptional activators that includes LysR, which regulates the E. coli lysine synthetase gene, and the NodD protein, which regulates expression of a number of genes involved in nodulation in Rhizobium. The lack of sequence homology to any known beta-lactam-binding protein suggests that AmpR does not bind directly to the beta-lactam inducer but interacts with a second messenger of unknown nature.
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PMID:Binding of the Citrobacter freundii AmpR regulator to a single DNA site provides both autoregulation and activation of the inducible ampC beta-lactamase gene. 278 68

The nifA gene of Klebsiella pneumoniae, which encodes the transcriptional activator of nif gene expression, was cloned into a number of plasmid vectors to obtain high-level synthesis of nifA product (NifA). When over-produced, NifA was very insoluble and it precipitated with the cell debris after cell lysis. Localization of beta-galactosidase activity from a nifA-lacZ translational fusion confirmed the insoluble nature of NifA. Analysis of two translational fusions in which the last six C-terminal amino acids of NifA were deleted suggests that these residues are required for activity.
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PMID:Over-production and characterization of the nifA gene product of Klebsiella pneumoniae--the transcriptional activator of nif gene expression. 284 61

The fnr gene of Escherichia coli encodes a transcriptional activator (FNR) which is required for the expression of a number of genes involved in anaerobic respiratory pathways. From the study of a translational fusion of fnr to the gene for beta-galactosidase (lacZ) it has been concluded that the fnr gene is expressed under both aerobic and anaerobic conditions and is subject to autoregulation and repression by glucose, particularly during anaerobic growth. These findings imply that during anaerobiosis the FNR protein adopts an active conformation, in which it functions both as a repressor of the fnr gene and as an activator of fnr-dependent genes. Sequences in the 5' non-coding region of fnr which could be involved in autoregulation are discussed. The fnr coding region was cloned into an expression vector which has allowed an amplification of FNR synthesis such that it accounts for about 2% of total cell protein. The ability to over-produce FNR in this way should be very useful for future biochemical studies.
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PMID:Regulation and over-expression of the fnr gene of Escherichia coli. 284 47

Expression of the soluble (SH) and membrane-bound (MBH) hydrogenases in the facultatively lithoautotrophic bacterium Alcaligenes eutrophus is dependent on the transcriptional activator HoxA and the alternative sigma factor sigma 54. Deletion analysis revealed that a region 170 bp upstream of the transcriptional start of the SH operon is necessary for high-level promoter activity. Mobility shift assays with DNA fragments containing the SH upstream region and purified beta-galactosidase-HoxA fusion protein isolated from Escherichia coli or authentic HoxA isolated by immunoaffinity chromatography from A. eutrophus failed to detect specific binding. In contrast, A. eutrophus extracts enriched for HoxA by heparin-Sepharose chromatography and ammonium sulfate fractionation produced a weak but discrete shift in the mobility of the target DNA. This effect was not observed with comparable extracts prepared from hoxA mutants. A similar experiment using antibodies against HoxA confirmed that HoxA was responsible for the observed mobility shift. Extracts prepared from a temperature-tolerant mutant of A. eutrophus gave a stronger retardation than did those from the wild type. Unlike the wild type, the hox(Tr) mutant is able to grow with hydrogen at temperatures above 33 degrees C because of a mutation in the regulatory gene hoxA. In this paper, we show that a single amino acid substitution (Gly-468-->Val) in the C-terminal part of HoxA is responsible for temperature tolerance. The SH upstream region also contains sequence motifs resembling the E. coli integration host factor (IHF) binding site, and purified E. coli IHF protein shifted the corresponding indicator fragment.
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PMID:Temperature tolerance of hydrogenase expression in Alcaligenes eutrophus is conferred by a single amino acid exchange in the transcriptional activator HoxA. 773 Feb 67

The divergently transcribed nasA gene and nasB operon are required for nitrate and nitrite assimilation in Bacillus subtilis. The beta-galactosidase activity of transcriptional lacZ fusions from the nasA and nasB promoters was high when cells were grown in minimal glucose medium containing poor nitrogen sources such as nitrate, proline, or glutamate. The expression was very low when ammonium or glutamine was used as the sole nitrogen source. The repression of the genes during growth on good sources of nitrogen required wild-type glutamine synthetase (GlnA), but not GlnR, the repressor of the glnRA operon. Primer extension analysis showed that the -10 region of each promoter resembles those of sigma A-recognized promoters. Between the divergently oriented nasA and nasB promoters is a region of dyad symmetry. Mutational analysis led to the conclusion that this sequence is required in cis for the activation of both nasA and nasB. The derepression of these genes in a glnA mutant also required this sequence. These results suggest that an unidentified transcriptional activator and glutamine synthetase function in the regulation of nasA and the nasB operon.
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PMID:Nitrogen regulation of nasA and the nasB operon, which encode genes required for nitrate assimilation in Bacillus subtilis. 783 89

In Pseudomonas aeruginosa, the transcriptional activator LasR and the Pseudomonas autoinducer PAI, are necessary for efficient transcriptional activation of the lasB gene, encoding elastase (L. Passador, J. M. Cook, M.J. Gambello, L. Rust, and B. H. Iglewski, Science 260:1127-1130, 1993). The transcriptional start points of lasI in Escherichia coli and P. aeruginosa were determined by S1 nuclease mapping. In the presence of both LasR and PAI, the start site, T1, is located at position -25 relative to the ATG translational start codon. A minor transcriptional start, T2, is found at position -13 when lasI is transcribed in the absence of either LasR or PAI in P. aeruginosa and E. coli, respectively. To begin to closely examine the regulation of lasI, whose product is involved in the synthesis of PAI, a lasI-lacZ fusion on a lambda phage was constructed to form monolysogens of E. coli MG4. Lysogens supplied only with either lasI or lasR via multicopy plasmids demonstrated no significant increase in beta-galactosidase expression compared with control levels. Lysogens in which both lasR and lasI were supplied in multicopy exhibited a 62-fold increase in expression, and a lysogen in which lasR was supplied in trans and which was grown in the presence of exogenous PAI exhibited a 60-fold increase. Thus, LasR and PAI are necessary for the full expression of lasI in E. coli. The interchangeability of the P. aeruginosa and Vibrio fischeri homologs LasR and LuxR and their respective autoinducers, PAI and VAI, as activators of lasI-lacZ was examined. Only the combination of LasR and PAI significantly increased the expression of lasI. The comparison of lasI-lacZ and lasB-lacZ expression lysogens grown in the presence of lasR and PAI revealed that half-maximal expression of lasI required 0.1 nM PAI, in contrast to the 1.0 nM PAI necessary for lasB half-maximal expression. These results suggest an autoinduction regulatory hierarchy in which LasR and low PAI concentrations primarily activate lasI expression in a regulatory loop. With the accumulation of PAI, secondary activation of virulence product genes such as lasB occurs.
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PMID:Activation of the Pseudomonas aeruginosa lasI gene by LasR and the Pseudomonas autoinducer PAI: an autoinduction regulatory hierarchy. 783 99

We have independently identified and DNA sequenced the INO2 locus by its close proximity to the KIN1 locus in Saccharomyces cerevisiae. Mutant strains in which the INO2 chromosomal locus has been deleted show pleiotropic phenotypes under growth conditions of inositol/choline availability. Many ino2 delta cells show delocalized cell growth resulting in large cells having aberrant shapes. These mutant cells may display nuclear segregation or positioning defects as well as defects in bud formation. Furthermore, homozygous ino2 delta-1 diploids fail to sporulate. Previous studies have shown that INO2 mutants are defective in phospholipid synthesis due to an inability to derepress the INO1 gene, the structural gene for inositol-1-phosphate synthase. To identify and determine the function of Ino2p in yeast cells, we raised antibodies to a beta-galactosidase/Ino2 fusion protein. The INO2 open reading frame codes for a 304 amino acid protein with a calculated molecular weight of 39.7 kDa. Immunoblot analysis reveals two Ino2-specific proteins of approximately 44 and 46 kDa. The 44 kDa species is localized to the nucleus. Ino2p is believed to function as a positive transcriptional activator in phospholipid synthesis. Our results suggest that it affects additional pathways important to polarized cell growth and division perhaps by functioning as a more general transcriptional factor.
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PMID:INO2, a regulatory gene in yeast phospholipid biosynthesis, affects nuclear segregation and bud pattern formation. 801 48

The sequences of two previously known tail genes, R and S, of the temperate bacteriophage P2 and the sequence of an additional open reading frame (orf-30) located between S and V, were determined. Amber mutations mapping within R and S, Ram3, Ram42, Ram23, Sam75, and Sam89 were sequenced and found to be within their corresponding open reading frames. We constructed overproducing plasmids for R and S and identified these proteins by SDS-PAGE of whole-cell lysates and Coomassie blue staining. The predicted molecular masses of proteins R and S were M(r) 17,400 and 17,300, respectively, although both polypeptides migrated more slowly during gel electrophoresis than would be expected from the sequence data. orf-30 occupies the strand opposite from RS and V and is preceded by several weak potential sigma 70-RNA polymerase promoters, some of which overlap with the V promoter. A construct that had the putative orf-30 promoter region upstream of the lacZ gene produced low levels of beta-galactosidase activity in vivo. Expression from the orf-30 promoter was not stimulated by the phage P4 transcriptional activator protein, delta, which acts at all the known P2 and P4 late promoters. Insertion mutagenesis showed that orf-30 was not an essential gene for P2 growth in Escherichia coli. None of the gene or protein sequences exhibited extensive homology to sequences in the nucleic acid and protein databases. However, the R protein contains a small region homologous to one in the phage T4 tail protein gp15, which is required for T4 tails to bind heads. We propose that R and S are tail completion proteins that are essential for stable head joining.
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PMID:Molecular cloning and characterization of bacteriophage P2 genes R and S involved in tail completion. 817 26

Transformed Saccharomyces cerevisiae cells overexpressing the Escherichia coli LacZ gene and the transcriptional activator GAL4, release in the external medium a fraction (from 2 to 10%) of the total beta-galactosidase activity (Porro et al., 1992b). It is known that this abnormal release of a cytoplasmic protein is related to a partial cell lysis of the yeast population, which is likely to be caused by the overexpression of the transcriptional activator GAL4. In the present paper we have characterized the GAL4-induced cell lysis phenomenon. The expression of the GAL4 gene causes morphological modifications and alteration of the cell size distribution. The cell lysis is independent of the expression of the heterologous LacZ gene and occurs in a specific subpopulation of cells (the parent cells) independently of the genealogical age, growth phase conditions and cell cycle progression. Lysis is preceded by a loss of the plasma membrane integrity as indicated by the uptake of ethidium bromide in unfixed cells. Computer analysis of simulated protein distributions indicates that cell lysis takes place in a sizeable aliquot (about 50%) of the parent cells, therefore profoundly altering the age structure of the population.
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PMID:Alteration of cell population structure due to cell lysis in Saccharomyces cerevisiae cells overexpressing the GAL4 gene. 834 73


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