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 Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) is one of the first EBV-encoded gene products expressed after infection of primary B lymphocytes. EBNA2 is essential for the growth-transforming potential of the virus and it functions as a transcriptional activator of a set of viral and cellular genes. Sequence-specific DNA-binding by EBNA2 has not been demonstrated but the molecule is targeted to specific DNA regions by a cellular protein, RBP-J kappa, which recognizes the GTGGGAA sequence present in the regulatory region of all EBNA2-responsive promoters defined so far. We have determined the contribution of a RBP-J kappa recognition sequence, an adjacent interferon-stimulated response element (ISRE) motif and a PU.1-binding site in the LMP1 regulatory sequence (LRS) to EBNA2-induced transactivation of the promoter by site-directed mutagenesis of LRS-carrying reporter plasmids. EBNA2 responsiveness was reduced by approximately twofold when either or both of the RBP-J kappa-binding and ISRE sequences were mutated. ISRE seemed to function as an EBNA2-independent positive element. On the other hand, mutation of the PU box resulted in a drastic reduction of EBNA2 responsiveness, irrespective of whether the RBP-J kappa site or the ISRE motif was present. A comparative study by deletion mutation identified regions of EBV B95-8 EBNA2 involved in the transactivation of the LMP1 and the EBNA Cp promoters. Two domains of EBNA2 defined by deletion of amino acids 247-337 and 437-476 were found to be important for the activation of both promoters, while two different domains corresponding to residues 4-18 and 118-198 were required solely for the LMP1 promoter. Thus, EBNA2 must activate the LMP1 and Cp promoters by different mechanisms. All deletions involved in transcriptional activation of the two promoters contained regions that are conserved in EBNA2 of B95-8 EBV (type 1), AG876 EBV (type 2) and herpesvirus papio origin.
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PMID:Domains of the Epstein-Barr virus nuclear antigen 2 (EBNA2) involved in the transactivation of the latent membrane protein 1 and the EBNA Cp promoters. 759 74

Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) is a transcriptional activator that is essential for EBV-driven B cell immortalization. EBNA2 is targeted to responsive promoters through interaction with a cellular DNA binding protein, C promoter binding factor 1 (CBF1). A transcriptional repression domain has been identified within CBF1. This domain also interacts with EBNA2, and repression is masked by EBNA2 binding. Thus, EBNA2 acts by countering transcriptional repression. Mutation at amino acid 233 of CBF1 abolishes repression and correlates with a loss-of-function mutation in the Drosophila homolog Su(H).
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PMID:Masking of the CBF1/RBPJ kappa transcriptional repression domain by Epstein-Barr virus EBNA2. 772 2

The Epstein-Barr virus EBNA2 protein is a transcriptional activator that achieves promoter specificity through interaction with the cellular DNA-binding protein CBF1/RBPJk. Within the amino acid 252-to-425 EBNA2 domain that targets CBF1/RBPJk lie three amino acid clusters, conserved regions (CR) 5, 6, and 7, that are retained in the Epstein-Barr virus type A and type B and herpesvirus papio proteins. To further define the important features of the targeting domain, we constructed EBNA2 polypeptides containing deletions in the targeting domain and double or triple point mutations in the conserved motifs. The ability of these polypeptides and the type B and herpesvirus papio domains to interact with CBF1/RBPJk was examined by performing electrophoretic mobility shift assays and correlated with the effect of the mutations on EBNA2 transactivation. Both human type B EBNA2 and herpesvirus papio EBNA2 bound CBF1/RBPJk efficiently. Mutation of hydrophobic residues in CR6 severely impaired CBF1/RBPJk interaction and transactivation, while mutation of CR5 led to a moderate decrease in both activities. Mutation of CR7 had only a minor effect. Synthetic peptides corresponding to each of the conserved motifs were also used as competitors in an electrophoretic mobility shift assay. Only the peptide representing CR6 (amino acids 318 to 327), and not a version of this peptide mutated at the tryptophan residues at positions 323 and 324 (WW323,324), could compete for EBNA2 complex formation with CBF1/RBPJk. Overall, the data indicated that CR5 contributes to an optimal interaction, perhaps through stabilizing contacts, while CR6 forms a crucial interface with CBF1/RBPJk. The peptide competition data are consistent with direct contacts between WW323,324 and CBF1/RBPJk.
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PMID:Contribution of conserved amino acids in mediating the interaction between EBNA2 and CBF1/RBPJk. 785 39

The Epstein-Barr virus (EBV) protein EBNA2, which is essential for the immortalization of human primary B cells by EBV, acts as a transcriptional activator of cellular and viral genes. Specific responsive elements have been characterized in several of the promoters activated by EBNA2. They all share the core sequence GTGGGAA. EBNA2 does not, however, bind to these sequences directly, but appears to be targeted to them by a cellular protein. A similar core sequence has recently been identified as a high-affinity binding site for the human recombination signal sequence binding protein RBP-J kappa. Here we provide evidence that RBP-J kappa binds to specific sequences in EBNA2-responsive elements. Our results also demonstrate that RBP-J kappa makes direct physical contact with EBNA2 in solution and recruits EBNA2 to its cognate DNA sequences, suggesting that RBP-J kappa may mediate EBNA2 transactivation of both cellular and viral genes.
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PMID:The human J kappa recombination signal sequence binding protein (RBP-J kappa) targets the Epstein-Barr virus EBNA2 protein to its DNA responsive elements. 798 60

The EBNA-2 protein is essential for the establishment of a latent Epstein-Barr virus (EBV) infection and for B-cell immortalization. EBNA-2 functions as a transcriptional activator that modulates viral latency gene expression as well as the expression of cellular genes, including CD23. We recently demonstrated that EBNA-2 transactivation of the EBV latency C promoter (Cp) is dependent on an interaction with a cellular DNA-binding protein, CBF1, for promoter targeting. To determine whether targeting via CBF1 is a common mechanism for EBNA-2-mediated transactivation, we have examined the requirements for activation of the cellular CD23 promoter. Binding of CBF1 to a 192-bp mapped EBNA-2-responsive region located at position -85 bp to -277 bp upstream of the CD23 promoter was detected in electrophoretic mobility shift assays. The identity of the bound protein as CBF1 was established by showing that the bound complex was competed for by the CBF1 binding site from the EBV Cp, that the bound protein could be supershifted with a bacterially expressed fusion protein' containing amino acids 252 to 425 of EBNA-2 but was unable to interact with a non-CBF1-binding EBNA-2 mutant (WW323SR), and that in UV cross-linking experiments, the Cp CBF1 binding site and the CD23 probe bound proteins of the same size. The requirement for interaction with CBF1 was demonstrated in a transient cotransfection assay in which the multimerized 192-bp CD23 response region was transactivated by wild-type EBNA-2 but not by the WW323SR mutant. Reporter constructions carrying multimerized copies of the 192-bp CD23 response region or multimers of the CBF1 binding site from the CD23 promoter were significantly less responsive to EBNA-2 transactivation than equivalent constructions carrying a multimerized region from the Cp or multimers of the CBF1 binding site from the Cp. Direct binding and competition assays using 30-mer oligonucleotide probes representing the individual CBF1 binding sites indicated that CBF1 bound less efficiently to the CD23 promoter and the EBV LMP-1 promoter sites than to the Cp site. To investigate the basis for this difference, we synthesized a series of oligonucleotides carrying mutations across the CBF1 binding site and used these as competitors in electrophoretic mobility shift assays. The competition experiments indicated that a central core sequence, GTGGGAA, common to all known EBNA-2-responsive elements, is crucial for CBF1 binding. Flanking sequences on either side of this core influence the affinity for CBF1.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:EBNA-2 upregulation of Epstein-Barr virus latency promoters and the cellular CD23 promoter utilizes a common targeting intermediate, CBF1. 805 21

Epstein-Barr virus nuclear antigen 2 (EBNA2) is a transcriptional activator of viral and cellular genes involved in B cell transformation by EBV and is targeted to EBV responsive promoters through interaction with cellular DNA binding proteins such as RBP-J kappa. To develop a conditional system in which the function of EBNA2 can be switched on and off, we have fused the hormone binding domain of the estrogen receptor to the N- or C-terminus of EBNA2. Here we show that after transient or stable transfer of these chimerical EBNA2 genes into human B cell lymphoma lines, transactivation of LMP1, TP1, and TP2 promoter constructs, expression of the cell surface markers CD21 and CD23, and binding of EBNA2 to its cellular partner RBP-J kappa are dependent on the presence of estrogen. The EBNA2 fusion proteins proved to be virtually inactive in the absence of hormone.
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PMID:Epstein-Barr virus nuclear antigen 2-estrogen receptor fusion proteins transactivate viral and cellular genes and interact with RBP-J kappa in a conditional fashion. 855 75

The Epstein-Barr virus (EBV) protein EBNA2 is a transcriptional activator that can be targeted to its DNA responsive elements by direct interaction with the cellular protein RBP-J kappa. RBP-J kappa is a ubiquitous factor, highly conserved between man, mouse and Drosophila, whose function in mammalian cells is largely unknown. Here we provide evidence that RBP-J kappa is a transcriptional repressor and, more importantly, that RBP-J kappa repression is mediated by a co-repressor. The function of the co-repressor could be counterbalanced by making a fusion protein (RBP-VP16) between RBP-J kappa and the VP16 activation domain. This RBP-VP16-mediated activation could be strongly increased by an EBNA2 protein deprived of its activation domain, but not by an EBNA2 protein incapable of making physical contact with RBP-J kappa. Our results suggest that EBNA2 activates transcription by both interfering with the function of a co-repressor recruited by RBP-J kappa and providing an activation domain.
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PMID:RBP-J kappa repression activity is mediated by a co-repressor and antagonized by the Epstein-Barr virus transcription factor EBNA2. 855 49

Transcription of MET genes in Saccharomyces cerevisiae depends on a transcriptional activator, the MET4 gene product (Met4p). Using in vitro mutagenesis, we isolated two mutant MET4 alleles encoding [Pro215]Met4p and [Ser156]Met4p. These mutations impeded Met4p's responsiveness to methionine in the media, and yeast cells carrying mutant alleles exhibited enhanced transcription of MET genes under repressing conditions. The enhanced transcription was dependent on the CBF1 gene, but did not compete with an excess of wild-type Met4p, suggesting that some changes in the affinity of Met4p to other factors might be involved in S-adenosylmethionine-mediated transcriptional regulation.
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PMID:Single point mutations in Met4p impair the transcriptional repression of MET genes in Saccharomyces cerevisiae. 867 45

Recent efforts have defined a cis-acting DNA regulatory element in plants, the C-repeat/dehydration responsive element (DRE), that stimulates transcription in response to low temperature and water deficit. Here we report the isolation of an Arabidopsis thaliana cDNA that encodes a C-repeat/DRE binding factor, CBF1 (C-repeat/DRE Binding Factor 1). Analysis of the deduced CBF1 amino acid sequence indicates that the protein has a molecular mass of 24 kDa, a potential nuclear localization sequence, and a possible acidic activation domain. CBF1 also has an AP2 domain, which is a DNA-binding motif of about 60 aa present in the Arabidopsis proteins APETALA2, AINTEGUMENTA, and TINY; the tobacco ethylene response element binding proteins; and numerous other plant proteins of unknown function. The transcript levels for CBF1, which appears to be a single or low copy number gene, did not change appreciably in plants exposed to low temperature or in detached leaves subjected to water deficit. Binding of CBF1 to the C-repeat/DRE was demonstrated in gel shift assays using recombinant CBF1 protein expressed in Escherichia coli. Moreover, expression of CBF1 in yeast was found to activate transcription of reporter genes containing the C-repeat/DRE as an upstream activator sequence but not mutant versions of the DNA element. We conclude that CBF1 can function as a transcriptional activator that binds to the C-repeat/DRE DNA regulatory element and, thus, is likely to have a role in cold- and dehydration-regulated gene expression in Arabidopsis.
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PMID:Arabidopsis thaliana CBF1 encodes an AP2 domain-containing transcriptional activator that binds to the C-repeat/DRE, a cis-acting DNA regulatory element that stimulates transcription in response to low temperature and water deficit. 902 78

The Epstein-Barr virus (EBV) EBNA2 protein is a transcriptional activator that regulates viral and cellular gene expression and is also essential for EBV-driven immortalization of B lymphocytes. The EBNA2-responsive enhancer in the viral latency C promoter (Cp) binds two cellular factors, CBF1 and CBF2. The precise role of the CBF2 protein for Cp enhancer function is presently unclear. CBF2 does not appear to interact with EBNA2 and binds just downstream of CBF1 between positions -339 and -368 in the Cp EBNA2 enhancer. Within this region an 8-bp sequence, CAGTGCGT, can be found, and a similar sequence is also located downstream of CBF1 binding sites in other EBNA2-responsive promoters. Previous studies have indicated that mutations and methylation in this sequence affect EBNA2 responsiveness. To investigate the requirements for CBF2 binding, we synthesized a series of oligonucleotides carrying double transversion mutations spanning both the conserved core sequence and outside flanking sequences. Surprisingly, mutations outside of the conserved core sequence in 4 bases immediately flanking the 5' end, GGTT, had the most deleterious effect on CBF2 binding. Mutations in the conserved core had a gradient effect, with those near the 5' end having the most deleterious effects on CBF2 binding. In addition, the affinities of CBF2 for binding to the LMP-1, LMP-2, and CD23 promoters were also measured. These promoters contain the conserved core but lack the 5' flanking GGTT motif and bound CBF2 weakly or not at all. Using Cp reporter plasmids containing CBF2 mutant binding sites, we were also able to show that at lower doses of EBNA2, Cp transactivation required a functional CBF2 binding site but that higher doses of EBNA2 transactivated CBF2 mutant promoters to 40% of wild-type levels. These assays indicate that CBF2 is important for EBNA2-mediated transactivation of the viral latency Cp. In addition, CBF2 activity was found to be associated with two polypeptides of 27 and 33 kDa.
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PMID:Characterization of the CBF2 binding site within the Epstein-Barr virus latency C promoter and its role in modulating EBNA2-mediated transactivation. 942 Feb 75


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