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 X-ray structure of the DNA binding domain of the yeast transcriptional activator protein GCN4 bound to a DNA fragment containing the sequence of the perfectly symmetrical ATF/CREB site has been solved to 3.0 A resolution. The architecture of this specific recognition complex supports the current model for bZIP proteins: a homodimer of parallel alpha-helices form an interhelix coiled-coil region via the leucine zipper, and the two N-terminal basic regions fit into the major groove of half sites on opposite sides of the DNA double helix. The structure shows that DNA flexibility plays the predominant role in the preservation of protein contacts with the symmetric ATF/CREB site (ATGACGTCAT) as compared to the pseudo-symmetric AP-1 target site (ATGACTCAT), overcoming the positional displacement of functional groups introduced by the additional G.C base-pair at the center of the ATF/CREB sequence.
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PMID:The X-ray structure of the GCN4-bZIP bound to ATF/CREB site DNA shows the complex depends on DNA flexibility. 837 81

The AraC protein, which regulates the L-arabinose operons in Escherichia coli, was dissected into two domains that function in chimeric proteins. One provides a dimerization capability and binds the ligand arabinose, and the other provides a site-specific DNA-binding capability and activates transcription. In vivo and in vitro experiments showed that a fusion protein consisting of the N-terminal half of the AraC protein and the DNA-binding domain of the LexA repressor dimerizes, binds well to a LexA operator, and represses expression of a LexA operator-beta-galactosidase fusion gene in an arabinose-responsive manner. In vivo and in vitro experiments also showed that a fusion protein consisting of the C-terminal half of the AraC protein and the leucine zipper dimerization domain from the C/EBP transcriptional activator binds to araI and activates transcription from a PBAD promoter-beta-galactosidase fusion gene. Dimerization was necessary for occupancy and activation of the wild-type AraC binding site.
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PMID:Functional domains of the AraC protein. 851 13

Molecular characterization of malignant melanoma of soft parts or soft tissue clear cell sarcoma which shares t(12;22) chromosome translocation revealed fusion of EWS with a transcriptional factor gene ATF-1. The EWS gene, which encodes an RNA binding protein, was also shown to be involved in Ewing sarcoma, related primitive neuroectodermal tumors and desmoplastic small round cell tumors. In order to understand the functional role of EWS-ATF-1 chimeric protein in human solid tumors, we have cloned the aberrant human ATF-1 (EWS-ATF-1) cDNA and studied its DNA binding, transcriptional activation properties and compared with normal ATF-1 protein. Our results demonstrate that EWS-ATF-1 binds weakly to DNA in vitro but functions as an efficient constitutive transcriptional activator unlike the normal ATF-1 which needs to be induced with cAMP. Deletion analysis revealed that EWS-fusion domain functions as a regulatory domain for the transcriptional activation properties of EWS-ATF-1 chimeric protein. Deletion of leucine zipper domain results in a loss of transcriptional activation of EWS-ATF-1 chimeric protein suggesting that protein-protein interaction play a role in the transcriptional activation properties of EWS-ATF-1. We demonstrate that EWS-fusion domain negatively regulates the DNA binding activity of EWS-ATF-1 chimeric protein. Therefore replacement of part of the amino-terminal kinase regulatory domain of ATF-1 protein with EWS regulatory domain results in an altered DNA binding, protein-protein interactions and transcriptional activation properties of EWS-ATF-1 causing deregulated gene expression which may be responsible for the genesis of t(12;22) chromosome translocation-bearing human solid tumors. Targeting the transcriptional cofactors (CBP, etc) by EWS-fusion proteins could be one of the mechanisms of activation of EWS-fusion proteins in human neoplasia.
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PMID:The EWS-ATF-1 gene involved in malignant melanoma of soft parts with t(12;22) chromosome translocation, encodes a constitutive transcriptional activator. 855 87

The GCR1 gene of Saccharomyces cerevisiae encodes a transcriptional activator that complexes with Rap1p and, through UASRPG elements (Rap1p DNA binding sites), stimulates efficient expression of glycolytic and translational component genes. To map the functionally important domains in Gcr1p, we combined multiple rounds of random mutagenesis in vitro with in vivo selection of functional genes to locate conserved, or hypomutable, regions. We name this method unigenic evolution, a statistical analysis of mutations in evolutionary variants of a single gene in an otherwise isogenic background. Examination of the distribution of 315 mutations in 24 variant alleles allowed the localization of four hypomutable regions in GCR1 (A, B, C, and D). Dispensable N-terminal (intronic) and C-terminal portions of the evolved region of GCR1 were included in the analysis as controls and were, as expected, not hypomutable. The analysis of several insertion, deletion, and point mutations, combined with a comparison of the hypomutability and hydrophobicity plots of Gcr1p, suggested that some of the hypomutable regions may individually or in combination correspond to functionally important surface domains. In particular, we determined that region D contains a putative leucine zipper and is necessary and sufficient for Gcr1p homodimerization.
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PMID:Unigenic evolution: a novel genetic method localizes a putative leucine zipper that mediates dimerization of the Saccharomyces cerevisiae regulator Gcr1p. 860 72

The SNF1 protein kinase has been widely conserved in plants and mammals. In Saccharomyces cerevisiae, SNF1 is essential for expression of glucose-repressed genes in response to glucose deprivation. Previous studies supported a role for SNF1 in relieving transcriptional repression. Here, we report evidence that SNF1 modulates function of a transcriptional activator, SIP4, which was identified in a two-hybrid screen for interaction with SNF1. The N terminus of the predicted 96-kDa SIP4 protein is homologous to the DNA-binding domain of the GAL4 family of transcriptional activators, with a C6 zinc cluster adjacent to a coiled-coil motif The C terminus contains a leucine zipper motif and an acidic region. When bound to DNA, a LexA-SIP4 fusion activates transcription of a reporter gene. Transcriptional activation by SIP4 is regulated by glucose and depends on the SNF1 protein kinase. Moreover, SIP4 is differentially phosphorylated in response to glucose availability, and phosphorylation requires SNF1. These findings suggest that the SNF1 kinase interacts with a transcriptional activator to modulate its activity and provide the first direct evidence for a role of SNF1 in activating transcription in response to glucose limitation.
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PMID:Yeast SNF1 protein kinase interacts with SIP4, a C6 zinc cluster transcriptional activator: a new role for SNF1 in the glucose response. 862 58

c-Jun and c-Fos belong to the bZIP class of transcriptional activator proteins, many of which have been implicated in the neoplastic transformation of cells. We are interested in engineering dominant-negative leucine zipper (LZ) peptides as a means of sequestering these proteins in vivo in order to suppress their transcriptional regulatory activity. Toward this end, we have developed a novel immunoassay for measuring the dimerization affinities of dimeric Jun and Fos complexes. This peptide-based ELISA relies on the fact that Jun and Fos preferentially form heterodimers via their leucine zipper domains. Recombinant Jun leucine zipper peptides (either native JunLZ or a V36 --> E point mutant) were labeled with biotin and specifically bound through a leucine zipper interaction to a FosLZ-glutathione S-transferase fusion protein adsorbed onto the wells of an ELISA tray. Jun:Fos complexes were subsequently detected using a recently developed streptavidin-based amplification system known as enzyme complex amplification [Wilson, M. R., & Easterbrook-Smith, S.B. (1993) Anal. Biochem. 209, 183-187]. This ELISA system can detect subnanomolar concentrations of Jun and Fos, thus allowing determination of the dissociation constants for complex formation. The dissociation constant for formation of the native JunLZ:FosLZ heterodimer at 37 degrees C was determined to be 0.99 +/- 0.30 nM, while that for JunLZ(V36E):FosLZ heterodimer was 0.90 +/- 0.13 microM. These results demonstrate that the novel peptide-based ELISA described herein is simple and sensitive and can be used to rapidly screen for potential dominant-negative leucine zipper peptides.
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PMID:Development of a sensitive peptide-based immunoassay: application to detection of the Jun and Fos oncoproteins. 870 10

Members of the small Maf family (MafK, MafF, and MafG) are basic region leucine zipper (bZip) proteins that can function as transcriptional activators or repressors. The dimer compositions of their DNA binding forms determine whether the small Maf family proteins activate or repress transcription. Using a yeast two-hybrid screen with a GAL4-MafK fusion protein, we have identified two novel bZip transcription factors, Bach1 and Bach2, as heterodimerization partners of MafK. In addition to a Cap'n'collar-type bZip domain, these Bach proteins possess a BTB domain which is a protein interaction motif; Bach1 and Bach2 show significant similarity to each other in these regions but are otherwise divergent. Whereas expression of Bach1 appears ubiquitous, that of Bach2 is restricted to monocytes and neuronal cells. Bach proteins bind in vitro to NF-E2 binding sites, recognition elements for the hematopoietic transcription factor NF-E2, by forming heterodimers with MafK. Furthermore, a DNA binding complex that contained MafK as well as Bach2 or a protein related closely to Bach2 was found to be present in mouse brain cells. Bach1 and Bach2 function as transcription repressors in transfection assays using fibroblast cells, but they function as a transcriptional activator and repressor, respectively, in cultured erythroid cells. The results suggest that members of the Bach family play important roles in coordinating transcription activation and repression by MafK.
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PMID:Bach proteins belong to a novel family of BTB-basic leucine zipper transcription factors that interact with MafK and regulate transcription through the NF-E2 site. 888 38

Opaque-2 (O2) encodes a transcriptional activator of the basic domain-leucine zipper (bZIP) class, which controls the expression level in maize endosperm of the 22kD alpha-zeins and a number of non-storage proteins. The interaction of the O2 protein at three clustered binding sites on an isolated 22 kD zein gene promoter has been investigated. O2 is shown to transactivate transcription from these sites in tobacco mesophyll protoplasts as well as in maize endosperm cells transformed by particle bombardment. The binding sites have been mutated by base exchanges, singly or in different combinations, to determine their contribution to transactivation in vivo in both the leaf protoplast and the maize endosperm system. The effect of these mutations on binding of O2 in vitro was determined by electrophoretic mobility shift assays (EMSA), using O2 protein expressed in E. coli. Two of the sites seemed to be equally effective in responding to Opaque-2 in vivo in both cell types, although one of them does not contain an ACGT core sequence, and has a lower affinity for O2 in vitro than the ACGT-containing binding site. A third site, which has the lowest affinity of all three, confers no detectable O2-dependent promoter activation alone, but significantly increases activation in combination with either one of the other sites. Hence, weaker O2 binding sites can still mediate major O2-dependent effects when present in target promoters in vivo.
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PMID:The role of multiple binding sites in the activation of zein gene expression by Opaque-2. 891 16

The microE3 E box within the immunoglobulin heavy-chain (IgH) enhancer binds several proteins of the basic helix-loop-helix-leucine zipper (bHLHzip) class, including TFE3, USF1, and Max. Both TFE3 and USF have been described as transcriptional activators, and so we investigated their possible roles in activating the IgH enhancer in vivo. Although TFE3 activated various enhancer-based reporters, both USF1 and Max effectively inhibited transcription. Inhibition by USF correlated with the lack of a strong activation domain and was the result of the protein neutralizing the microE3 site. The effects of dominant-negative derivatives of TFE3 and USF1 confirmed that TFE3, or a TFE3-like protein, is the primary cellular bHLHzip protein that activates the IgH enhancer. In addition to providing a physiological role for TFE3, our results call into question the traditional view of USF1 as an obligate transcriptional activator.
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PMID:Selective utilization of basic helix-loop-helix-leucine zipper proteins at the immunoglobulin heavy-chain enhancer. 897 81

In the maize endosperm, the Opaque2 (O2) basic leucine zipper transcriptional activator regulates the expression of a subset of the zein seed storage protein gene family. Immunodetection of wild-type or mutant O2 polypeptides fractionated by SDS-PAGE resolved a closely spaced doublet migrating in the 68- to 72-kD range, whereas by using isoelectric focusing, seven to nine isoforms were detected for each allele. Phosphatase treatment simplified the protein patterns to a single band corresponding to the nonphosphorylated component. In vivo and in vitro labeling confirmed that O2 can be phosphorylated. In protein gel blots probed with DNA, only the nonphosphorylated and hypophosphorylated O2 polypeptides were able to bind an oligonucleotide containing the O2 binding sequence. Upon in situ dephosphorylation of the focused isoforms by phosphatase treatment of the isoelectric focusing filter, the hyperphosphorylated forms acquired DNA binding activity. The ratio among the various isoforms remained constant throughout the developmental stages of endosperm growth but changed from daytime to nighttime, with a significant increase of the hyperphosphorylated forms during the night period. These results indicate that O2 exists in vivo as a pool of differently phosphorylated polypeptides and demonstrate that O2 DNA binding activity is modulated by a phosphorylation/dephosphorylation mechanism that appears to be influenced by environmental conditions.
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PMID:Phosphorylation of Opaque2 changes diurnally and impacts its DNA binding activity. 901 67


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