UNIPROT:P51532 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

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

Effects of sibiromicyn, distamicyn A and its analogs on binding to DNA and to poly(dA).poly(dT) are reported for a 23-amino acid synthetic zinc-binding peptide, a part of the DNA-binding domain of the transcriptional activator GAL-4. Circular dichroism and fluorometry have shown that the synthetic peptide and two distamicyn A analogs compete for binding sites on DNA and on poly(dA).poly(dT). Antibiotic sibiromycin which forms a covalent bond with a guanine 2-amino group in the minor DNA groove can displace the peptide from a 19 bp self-complementary oligonucleotide serving as a specific target site for Gal-4 protein. The peptide is shown to bind to a glucosylated phage T2 DNA, but its affinity to T2 DNA is weaker than to calf thymus DNA under the same conditions. A method to estimate binding constant and size of the binding site for the synthetic peptide and poly(dA).poly(dT) is proposed based on the binding isotherms of distamycin analogs in the absence and in the presence of the peptide. Using isotherms of binding to poly(dA).poly(dT) for two distamycin analogs with binding constants differing 60-fold, the binding constant of the peptide in the presence of 0.1 M NaCl is estimated as 1.4.10(7)-1.8.10(7) M-1.
...
PMID:[A synthetic zinc chelating peptide competes for DNA binding sites with antibiotics, adsorbed in a minor DNA groove]. 778 40

Expression of the GAL genes of Saccharomyces cerevisiae is induced during growth on galactose by a well-characterized regulatory mechanism that relieves Gal80p inhibition of the Gal4p transcriptional activator. Growth on glucose overrides induction by galactose. Glucose repression acts at three levels to reduce GAL1 expression: (i) it reduces the level of functional inducer in the cell; (ii) it lowers cellular levels of Gal4p by repressing GAL4 transcription; and (iii) it inhibits Gal4p function through a repression element in the GAL1 promoter. We quantified the amount of repression provided by each mechanism by assaying strains with none, one, two, or all three of the repression mechanisms intact. In a strain lacking all three repression mechanisms, there was almost no glucose repression of GAL1 expression, suggesting that these are the major, possibly the only, mechanisms of glucose repression acting upon the GAL genes. The mechanism of repression that acts to reduce Gal4p levels in the cell is established slowly (hours after glucose addition), probably because Gal4p is stable. By contrast, the repression acting through the upstream repression sequence element in the GAL1 promoter is established rapidly (within minutes of glucose addition). Thus, these three mechanisms of repression collaborate to repress GAL1 expression rapidly and stringently. The Mig1p repressor is responsible for most (possibly all) of these repression mechanisms. We show that for GAL1 expression, mig1 mutations are epistatic to snf1 mutations, indicating that Mig1p acts after the Snf1p protein kinase in the glucose repression pathway, which suggests that Snf1p is an inhibitor of Mig1p.
...
PMID:Multiple mechanisms provide rapid and stringent glucose repression of GAL gene expression in Saccharomyces cerevisiae. 819 26

The Saccharomyces cerevisiae transcriptional activator GAL4 is regulated by the presence of available carbon sources. Galactose induces activity by inhibiting the negative regulator GAL80, while glucose, the preferred carbon source, antagonizes GAL4 function by several mechanisms. In the present study we present evidence that one mechanisms for inhibition of GAL transcription by glucose involves direct inhibition of the GAL4 protein. We demonstrate that a large, previously uncharacterized, central region of GAL4 contains at least three 'inhibitory domains' and a 'glucose response domain' (GRD). Deletion of the entire central region eliminates direct inhibition of GAL4 by glucose, and furthermore, fusion of the central region to a heterologous transcriptional activator confers inhibition by glucose. The central region inhibitory domains constitutively inhibit transcriptional activation when the GRD is absent. Direct inhibition of GAL4 activity can be detected within 30 min following glucose addition and may represent an early mechanism promoting a switch from galactose to glucose utilization. A model for the regulatory role of the central region is presented, involving interaction with an additional protein that inhibits GAL4 activity when glucose is present.
...
PMID:GAL4 is regulated by a glucose-responsive functional domain. 846 96

The concentration of the transcriptional activator LAC9 (KlGAL4) of Kluyveromyces lactis is moderately regulated by the carbon source as is the case for GAL4, its homolog in Saccharomyces cerevisiae. Expression of the LAC9 gene is induced about twofold in galactose. This induction is due to autoregulation. The LAC9 gene product binds to a low-affinity binding site in the LAC9 promoter and moderately activates transcription in response to galactose above a basal level. As for the LAC9-controlled metabolic genes, induction of LAC9 is inhibited in the presence of glucose. This inhibition of induction is a prerequisite for glucose repression of the lactose-galactose metabolic pathway. On the other hand, induced LAC9 levels are required for optimal growth on galactose, since mutating the LAC9 binding site in the LAC9 promoter resulted in poor growth and reduced expression of LAC9-controlled genes. Thus, in addition to the GAL80-dependent regulation by protein-protein interaction, the regulation of LAC9 gene expression is an important parameter in determining carbon source control of the LAC-GAL regulon. Although the mode of control is different, the pattern of LAC9 gene regulation resembles that of the S. cerevisiae GAL4 gene, being lower in glucose and glucose-galactose than in galactose.
...
PMID:Expression of the transcriptional activator LAC9 (KlGAL4) in Kluyveromyces lactis is controlled by autoregulation. 847 61

Transcription of the genes required for utilization of galactose in Saccharomyces cerevisiae is controlled primarily by the transcriptional activator protein GAL4. The upstream activating sequences for galactose (UASG) of most GAL genes have multiple sites to which GAL4 can bind. In this report we compare the binding properties of wild type GAL4 and derivatives of GAL4 bearing the N-terminal DNA-binding domain to multiple DNA-binding sites in vitro. To produce wild type GAL4, we constructed a recombinant baculovirus for expression in insect cells. Recombinant wild type GAL4 was found to bind efficiently to an oligonucleotide containing a near-consensus 17-mer GAL4 DNA-binding site in electrophoretic mobility shift assays. Footprinting experiments revealed that wild type GAL4 binds cooperatively to the four GAL4 DNA-binding sites of the GAL1-10 UASG; however, in contrast an N-terminal fragment of GAL4 containing only the DNA-binding/dimerization domains binds to each of these sites with slightly different affinity. With increasing concentrations of GAL4(1-147), the four sites become filled in the following order: site II, site IV, site I, and site III. In experiments with wild type GAL4, these four sites become fully occupied at approximately the same concentration of protein. In footprints of wild type GAL4 on the USAG, enhancements and protections of DNase I-sensitive cleavages are detectable between sites III and IV, indicative of formation of a loop between these distantly spaced sites. Binding of wild type GAL4 to a strong near-consensus binding site assists binding to an adjacent mutant site in both electrophoretic mobility shift and footprinting assays. GAL4(1-147) and GAL4(1-147) fused to portions of GAL4's activating region II were incapable of cooperative DNA binding in our assays. We conclude from these observations that wild type GAL4 has a cooperative DNA-binding function that is distinct from the DNA binding and dimerization or transcriptional activation functions, and likely plays and important role in precise regulation of GAL gene transcription.
...
PMID:Wild type GAL4 binds cooperatively to the GAL1-10 UASG in vitro. 848 50

Accumulating evidence supports the hypothesis that tumor-suppressor p53 can act as a transcriptional activator. Insertion of high-affinity p53 DNA binding sites upstream of a promoter yields a p53-responsive vector. Chimeric proteins fusing p53 and the GAL4 DNA-binding domain demonstrate the presence of a transcriptional activating domain in the N-terminus of p53. GAL4-p53 chimeras constructed using naturally occurring p53 mutations at either codon 141 (Tyr-141) or 175 (His-175) of p53 had little ability to activate the reporter gene; in contrast, mutations at either codon 248 (Trp-248) or 273 (His-273) produced greater transcriptional activities than did wild-type p53. GAL4 chimeras can be used to analyse interactions between different domains of p53 and between different p53 alleles; a DNA binding site is defined, and a simple measurement can be made of function. We had expected that coexpression of GAL4 chimeras and p53 alleles would squelch transcriptional activation downstream of GAL binding sites. Surprisingly, coexpression of either p53 (Trp-248) or (His-273) with the GALA-p53 (wild-type, His-273, Trp-248, His-175, Tyr-141) effectors conferred an increase in transcriptional activation as compared with the effector alone. Oligomerization of p53 alleles with GAL4-p53 chimeras could underlie this effect, leading to an increase in transcription-activating motifs near the promoter. To test this possibility, we constructed a GAL4-p53 C-terminal chimera with p53 residues 160-393, lacking the transcriptional activating domain but retaining regions believed to be important in p53 oligomerization. Neither GAL4-p53 (C-terminus) nor p53 expression vectors were able to transactivate G5E1B-CAT alone. Both p53 (His-273) and (Trp-248) co-expressed with GAL4-p53 (C-terminus) were able to transactivate the G5E1B-CAT reporter gene; in contrast, p53 (Tyr-141) was not able to activate transcription. p53 (Tyr-141/His-273) behaved as a dominant negative mutant and inhibited the ability of the combination of p53 (His-273) and GAL4-p53 (C-terminus) to stimulate the reporter gene. Double immunoprecipitation by sequentially using GAL4 and p53 antibodies showed that p53 (His-273) and (Tyr-141/His-273), but not p53 (Tyr-141), can efficiently oligomerize in vivo to the C-terminal region of p53. Transcriptional activating function of p53 may be modulated by oligomerization; some mutations, such as His-273 and Trp-248, participate in these functions.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Mutant p53 proteins have diverse intracellular abilities to oligomerize and activate transcription. 851 Sep 27

Gal4p-mediated activation of galactose gene expression in Saccharomyces cerevisiae normally requires both galactose and the activity of Gal3p. Recent evidence suggests that in cells exposed to galactose, Gal3p binds to and inhibits Ga180p, an inhibitor of the transcriptional activator Gal4p. Here, we report on the isolation and characterization of novel mutant forms of Gal3p that can induce Gal4p activity independently of galactose. Five mutant GAL3(c) alleles were isolated by using a selection demanding constitutive expression of a GAL1 promoter-driven HIS3 gene. This constitutive effect is not due to overproduction of Gal3p. The level of constitutive GAL gene expression in cells bearing different GAL3(c) alleles varies over more than a fourfold range and increases in response to galactose. Utilizing glutathione S-transferase-Gal3p fusions, we determined that the mutant Gal3p proteins show altered Gal80p-binding characteristics. The Gal3p mutant proteins differ in their requirements for galactose and ATP for their Gal80p-binding ability. The behavior of the novel Gal3p proteins provides strong support for a model wherein galactose causes an alteration in Gal3p that increases either its ability to bind to Gal80p or its access to Gal80p. With the Gal3p-Gal80p interaction being a critical step in the induction process, the Gal3p proteins constitute an important new reagent for studying the induction mechanism through both in vivo and in vitro methods.
...
PMID:Novel Gal3 proteins showing altered Gal80p binding cause constitutive transcription of Gal4p-activated genes in Saccharomyces cerevisiae. 911 26

The GAL4 protein belongs to a large class of fungal transcriptional activator proteins encoding within their DNA-binding domains (DBD) six cysteines that coordinate two atoms of zinc (the Zn2Cys6 domain). In an effort to characterize the interactions between the Zn2Cys6 class transcriptional activator proteins and their DNA-binding sites, we have replaced in the full-length GAL4 protein small regions of the Zn2Cys6 domain with the analogous regions of another Zn2Cys6 protein called PPR1 an activator of pyrimidine biosynthetic genes. Alterations between the first and third cysteines abolished binding to GAL4 (upstream activation sequence of GAL (UASG)) or PPR1 (upstream acitvation sequence of UAS) DNA-binding sites and severely reduced transcriptional activation in yeast. In contrast, alterations between the third and fourth cysteines had only minor effects on binding to UASG but led to substantial decreases in activation in both yeast and a mammalian cell line. In the crystal structure of the GAL4 DBD-UASG complex (Marmorstein, R., Carey, M., Ptashne, M., and Harrison, S. C. (1992) Nature 356, 408-414), this region is facing away from the DNA, making it likely that there exists within the GAL4 DBD an accessible domain important in activation.
...
PMID:Alterations in the GAL4 DNA-binding domain can affect transcriptional activation independent of DNA binding. 959 20

The transcriptional induction of the GAL genes of Saccharomyces cerevisiae occurs when galactose and ATP interact with Gal3p. This protein-small molecule complex associates with Gal80p to relieve its inhibitory effect on the transcriptional activator Gal4p. Gal3p shares a high degree of sequence homology to galactokinase, Gal1p, but does not itself possess galactokinase activity. By constructing chimeric proteins in which regions of the GAL1 gene are inserted into the GAL3 coding sequence, we have been able to impart galactokinase activity upon Gal3p as judged in vivo and in vitro. Remarkably, the insertion of just two amino acids from Gal1p into the corresponding region of Gal3p confers galactokinase activity onto the resultant protein. The chimeric protein, termed Gal3p+SA, retains its ability to efficiently induce the GAL genes. Kinetic analysis of Gal3p+SA reveals that the K(m) for galactose is similar to that of Gal1p, but the K(m) for ATP is increased. The chimeric enzyme was found to have a decreased turnover number in comparison to Gal1p. These results are discussed in terms of both the mechanism of galactokinase function and that of transcriptional induction.
...
PMID:The insertion of two amino acids into a transcriptional inducer converts it into a galactokinase. 1073 89

The Gal system of Saccharomyces cerevisiae is a paradigm for eukaryotic gene regulation. Expression of genes required for growth on galactose is regulated by the transcriptional activator Gal4. The activation function of Gal4 has been localized to 34 amino acids near the C terminus of the protein. The gal4D allele of GAL4 encodes a truncated protein in which only 14 amino acids of the activation domain remain. Expression of GAL genes is dramatically reduced in gal4D strains and these strains are unable to grow on galactose as the sole carbon source. Overexpression of gal4D partially relieves the defect in GAL gene expression and allows growth on galactose. A search for extragenic suppressors of gal4D identified recessive mutations in the SUG1 and SUG2 genes, which encode ATPases of the 19S regulatory complex of the proteasome. The proteasome is responsible for the ATP-dependent degradation of proteins marked for destruction by the ubiquitin system. It has been commonly assumed that effects of SUG1 and SUG2 mutations on transcription are explained by alterations in the proteolysis of gal4D protein. We have investigated this assumption. Surprisingly, we find that SUG1 and SUG2 alleles that are unable to suppress gal4D cause a larger increase in gal4D protein levels than do suppressing alleles. In addition, mutations in genes encoding subunits of the proteolytic 20S sub-complex of the proteasome increase the levels of gal4D protein but do not rescue its transcriptional activity. Therefore, an alteration in the proteolysis of gal4D by the proteasome cannot explain the effects of mutations in SUG1 and SUG2 on expression of GAL genes. These findings suggest that the 19S regulatory complex may play a more direct role in transcription.
...
PMID:Evidence that proteolysis of Gal4 cannot explain the transcriptional effects of proteasome ATPase mutations. 1115 78

<< Previous 1 2 3 4 5 Next >>