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)

Complete 1H NMR resonance assignments are presented for the cysteine rich region of the DNA binding domain of the yeast transcriptional activator GAL4. The protein contains short helical regions between Asp-12 and Leu-19 and between Lys-30 and Trp-36. It is clearly distinct from the C2H2 class of zinc finger protein typified by the Xenopus laevis transcription factor (TF)IIIA. We also find that the first SP(X)(X) sequence, a recently proposed DNA binding motif (residues 41 to 44), appears to be tightly packed against the metal binding domain.
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PMID:Complete assignment of the 1H NMR spectrum and secondary structure of the DNA binding domain of GAL4. 226 11

Previous work has shown that a synthetic peptide corresponding to the leucine zipper region of the yeast transcriptional activator GCN4 forms a stable dimer of alpha-helices and that the helices are oriented in a parallel manner. Two-dimensional nuclear magnetic resonance spectroscopy (NMR) is used here to demonstrate that the helix is continuous for at least 32 of the 33 residues in the peptide. The results also indicate that the dimer is symmetric. It is therefore unlikely that the interdigitation model for the structure of leucine zippers is correct, since interdigitation of leucine residues in a parallel dimer would lead to an asymmetric structure. The data are consistent with a coiled-coil structure.
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PMID:Secondary structure of a leucine zipper determined by nuclear magnetic resonance spectroscopy. 233 72

A structural motif for DNA-binding proteins, the 'leucine zipper', has been proposed for the jun, fos and myc gene products, the yeast transcriptional activator GCN4, and the C/EBP enhancer-binding protein. These proteins all contain a region with four or five leucine residues spaced exactly seven amino acid residues apart whose sequence is consistent with the formation of an amphipathic alpha-helix. It has been proposed that the leucine zipper consists of two interdigitated alpha-helices, one from each monomer, that constitute the dimerization function necessary for high-affinity binding to DNA; an adjacent region of basic residues is thought to be responsible for specific protein-DNA contacts. In support of this model, substitution of the leucine residues within the motif can abolish dimerization and DNA-binding, and a synthetic peptide corresponding to the GCN4 leucine zipper forms alpha-helical dimers. Despite the conserved leucine residues, however, each protein has a distinct dimerization specificity. Specifically, GCN4 homodimer, Jun homodimer and Fos-Jun heterodimer proteins bind to the same DNA site, whereas Fos is unable to form homodimers, bind DNA, or interact with GCN4 (refs 8-14). Here, we alter the dimerization specificity of Fos by precisely replacing its leucine zipper with that from GCN4. This Fos-GCN4 chimaeric protein is able to bind to the target site in the absence of Jun, and can form DNA-binding heterodimers with GCN4 but not with Jun. These results indicate that the leucine zipper is sufficient to confer dimerization specificity and strongly suggest that Fos contacts DNA directly.
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PMID:Changing fos oncoprotein to a jun-independent DNA binding protein with GCN4 dimerization specificity by swapping "leucine zippers". 250 87

LEU3 of Saccharomyces cerevisiae encodes an 886-amino-acid polypeptide that activates transcription of at least five genes by binding to an upstream decanucleotide sequence. This activation is dependent on the inducer alpha-isopropylmalate, the synthesis of which is repressed by leucine. We created a 285-amino-acid LEU3 derivative by removing a large block of internal sequences, including a dense cluster of acidic residues. This deletion protein bound to the decanucleotide sequence in vitro and activated gene expression in vivo. In contrast to wild-type LEU3, the truncated LEU3 protein was an effective transcriptional activator when alpha-isopropylmalate synthesis was repressed by leucine.
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PMID:A large internal deletion converts yeast LEU3 to a constitutive transcriptional activator. 267 86

We previously reported the isolation of yeast mutants that seem to affect the function of certain autonomously replicating sequences (ARSs). These mutants are known as mcm for their defect in the maintenance of minichromosomes. We have now characterized in more detail one ARS-specific mutation, mcm1-1. This Mcm1 mutant has a second phenotype; MAT alpha mcm1-1 strains are sterile. MCM1 is non-allelic to other known alpha-specific sterile mutations and, unlike most genes required for mating, it is essential for growth. The alpha-specific sterile phenotype of the mcm1-1 mutant is manifested by its failure to produce a normal amount of the mating pheromone, alpha-factor. In addition, transcripts of the MF alpha 1 and STE3 genes, which encode the alpha-factor precursor and the alpha-factor receptor, respectively, are greatly reduced in this mutant. These and other properties of the mcm1-1 mutant suggest that the MCM1 protein may act as a transcriptional activator of alpha-specific genes. We have cloned, mapped and sequenced the wild-type and mutant alleles of MCM1, which is located on the right arm of chromosome XIII near LYS7. The MCM1 gene product is a protein of 286 amino acid residues and contains an unusual region in which 19 out of 20 residues are either aspartic or glutamic acid, followed by a series of glutamine tracts. MCM1 has striking homology to ARG80, a regulatory gene of the arginine metabolic pathway located about 700 base-pairs upstream from MCM1. A substitution of leucine for proline at amino acid position 97, immediately preceding the polyanionic region, was shown to be responsible for both the alpha-specific sterile and minichromosome-maintenance defective phenotypes of the mcm1-1 mutant.
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PMID:Saccharomyces cerevisiae protein involved in plasmid maintenance is necessary for mating of MAT alpha cells. 306 8

The expression of the pap pilus operon of Escherichia coli is under a phase-variation control mechanism in which cells undergo a reversible transition between transcriptionally active (phase ON) and inactive (phase OFF) states. In this study, we explore the roles of leucine-responsive regulatory protein (Lrp) and the histone-like protein H-NS in the regulation of pap phase variation. Our data indicate that the phase OFF state results from repression of the intrinsically active papBA promoter by Lrp and H-NS, each of which can act independently as transcriptional repressors. Lrp requires pap DNA sequences upstream of the papBA promoter for its repressor activity whereas H-NS does not. In contrast, in the ON state, Lrp, in conjunction with PapI, activates pap transcription. This activation is not merely a result of alleviating the H-NS mediated repression, but induces a level of transcription that is eightfold higher than the basal level of transcription from the papBA promoter measured in the absence of both H-NS and Lrp. Analysis of Lrp activation mutants indicates that binding of Lrp to pap DNA sequences is not sufficient for transcription activation, consistent with a model in which an additional domain of Lrp interacts with the transcriptional apparatus. Together, our results show that Lrp functions as a transcriptional activator in phase-ON cells and as a repressor of basal transcription in phase-OFF cells. Because pap phase variation occurs in the absence of H-NS, it is not clear what role this regulatory protein plays in pap gene regulation.
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PMID:Leucine-responsive regulatory protein plays dual roles as both an activator and a repressor of the Escherichia coli pap fimbrial operon. 749 79

Leucine zipper peptides provide simple model systems for studying both the intramolecular and intermolecular interactions that govern protein folding. The synthetic 33-residue peptide GCN4-p1, derived from the yeast transcriptional activator GCN4, forms a stable biomolecular coiled-coil structure [O'Shea, E. K., Klemm, J. D., Kim, P. S., & Alber, T. (1991) Science 254, 539-544]. The guanidine-HCl induced equilibrium unfolding of this peptide at 5 degrees C and pH 7.0 yields a standard state free energy of 10.49 +/- 0.23 kcal (mol dimer)-1 when fit to a two-state model involving the native dimer and the unfolded monomer. The unfolding and refolding kinetics of GCN4-p1 were monitored by stopped-flow circular dichroism spectroscopy as a function of both peptide concentration and final denaturant concentration. The unfolding kinetics displayed single-exponential behavior, consistent with a unimolecular reaction. The refolding kinetics, which are dependent on both peptide and guanidine concentration, are well described by a simple bimolecular association reaction. A simultaneous fit of all of the unfolding and refolding kinetic data to the model, N2[symbol: see text]2U, yields refolding and unfolding rate constants in the absence of denaturant of 4.2 x 10(5) M-1 S-1 and 3.3 x 10(-3) S-1, respectively. The equilibrium unfolding curve is accurately predicted from these rate constants, providing further support for the validity of the two-state kinetic model.
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PMID:Probing the folding mechanism of a leucine zipper peptide by stopped-flow circular dichroism spectroscopy. 754 36

The product of the Saccharomyces cerevisiae LEU3 gene, Leu3p, is a transcriptional activator which regulates leucine biosynthesis in response to intracellular levels of leucine through the biosynthetic intermediate alpha-isopropylmalate. We devised a novel assay to examine the DNA site occupancy of Leu3p under different growth conditions, using a reporter gene with internal Leu3p-binding sites. Expression of the reporter is inhibited by binding of nuclear Leu3p to these sites; inhibition is dependent on the presence of the sites in the reporter, on the integrity of the Leu3p DNA-binding domain, and, surprisingly, on the presence of a transcriptional activation domain in the inhibiting protein. By this assay, Leu3p was found to occupy its binding site under all conditions tested, including high and low levels of leucine and in the presence and absence of alpha-isopropylmalate. The localization of Leu3p to the nucleus was confirmed by immunofluorescence staining of cells expressing epitope-tagged Leu3p derivatives. We conclude that Leu3p regulates transcription in vivo without changing its intracellular localization and DNA site occupancy.
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PMID:Detection of leucine-independent DNA site occupancy of the yeast Leu3p transcriptional activator in vivo. 762 98

We have characterized a stress-responsive transcriptional activation domain of mouse heat shock factor 1 (HSF1) by using chimeric GAL4-HSF1 fusion proteins. Fusion of the GAL4 DNA-binding domain to residues 124 to 503 of HSF1 results in a chimeric factor that binds DNA yet lacks any transcriptional activity. Transactivation is acquired upon exposure to heat shock or by deletion of a negative regulatory domain including part of the DNA-binding-domain-proximal leucine zippers. Analysis of a collection of GAL4-HSF1 deletion mutants revealed the minimal region for the constitutive transcriptional activator to map within the extreme carboxyl-terminal 108 amino acids, corresponding to a region rich in acidic and hydrophobic residues. Loss of residues 395 to 425 or 451 to 503, which are located at either end of this activation domain, severely diminished activity, indicating that the entire domain is required for transactivation. The minimal activation domain of HSF1 also confers enhanced transcriptional response to heat shock or cadmium treatment. These results demonstrate that the transcriptional activation domain of HSF1 is negatively regulated and that the signal for stress induction is mediated by interactions between the amino-terminal negative regulator and the carboxyl-terminal transcriptional activation domain.
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PMID:The carboxyl-terminal transactivation domain of heat shock factor 1 is negatively regulated and stress responsive. 762 25

The mechanism by which human immunodeficiency virus type 1 Tat transactivates the long terminal repeat promoter is not understood. It is generally believed that Tat has one or more transcription factors as its cellular target. One might expect a cellular target for Tat to possess several properties, including (i) the ability to bind to the Tat activation region, (ii) the possession of a transcriptional activation domain, and (iii) the ability to contact the cellular transcription machinery. Here we describe the cloning, expression, and characterization of a human protein, termed TAP (Tat-associated protein), which possesses some of these properties. TAP is highly conserved in eukaryotes and is expressed in a variety of human tissues. The major intracellular species of TAP is a highly acidic 209-amino-acid protein that likely is formed by removal of a highly basic 70-amino-acid N-terminal segment from a primary translation product. By deletion analysis, we have identified a TAP C-terminal region rich in acidic amino acids and leucine residues which acts as a strong transcriptional activator when bound through GAL4 sites upstream of the core long terminal repeat promoter, as well as flanking sequences that mask the activation function. Amino acid substitution of two leucine residues within the core activation region results in loss of the TAP activation function. Two lines of evidence suggest that Tat interacts with TAP in vivo. First, promoter-bound Tat can recruit a TAP/VP16 fusion protein to the promoter. Second, transiently expressed Tat is found associated with endogenous TAP, as demonstrated by coimmuno-precipitation analysis. As shown in an accompanying report, the TAP activation region binds the Tat core activation region and general transcription factor TFIIB (L. Yu, P.M. Loewenstein, Z. Zhang, and M. Green, J. Virol. 69:3017-3023, 1995). These combined results suggest the hypothesis that TAP may function as a coactivator that bridges Tat to the general transcription machinery of the cell via TFIIB.
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PMID:Molecular cloning and characterization of a cellular protein that interacts with the human immunodeficiency virus type 1 Tat transactivator and encodes a strong transcriptional activation domain. 770 27


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