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 Tax protein of the human T-cell leukemia virus type I (HTLV-I) serves as a potent transcriptional activator of its own long terminal repeat as well as select cellular genes, including interleukin-2 and the alpha subunit of the interleukin-2 receptor. Tax activation of these two growth-related genes appears to involve the induced nuclear expression of DNA-binding proteins that specifically engage related kappa B enhancer elements present in the 5' regulatory regions of these genes. In human T cells, kappa B enhancer-binding activity has been discerned as an unexpectedly large family of UV cross-linked nucleoprotein adducts, termed p50, p55, p75, and p85. The protein components of each of these DNA-protein adducts have been shown to share structural similarity with the v-rel oncogene product. The p55 adduct is composed of the 50-kDa subunit of NF-kappa B derived from a 105-kDa precursor polypeptide, while the p50 adduct contains a smaller protein that is closely related to NF-kappa B p50. The p75 adduct contains the 65-kDa subunit of NF-kappa B, while the p85 adduct is composed of the human c-rel proto-oncogene product. We now demonstrate that HTLV-I Tax, in the absence of other viral pX gene products, is capable of inducing the nuclear expression of all four of these kappa B-binding proteins in human T cells, with most marked effects involving c-Rel and NF-kappa B p65. Tax induction of the nuclear expression of c-Rel and NF-kappa B p50 is regulated, at least in part, at a pretranslational level involving increases in c-rel and NF-kappa B p105 mRNA expression. To study the pattern of expression of these kappa B-specific proteins in cells infected with the whole HTLV-I, seven cloned HTLV-I-infected T-cell lines were established from the peripheral blood of patients with adult T-cell leukemia. Of note, only three of these seven cell lines produced Tax, and c-rel mRNA and nuclear protein expression was confined to these three cell lines. In contrast, NF-kappa B p50 and NF-kappa B p65 were constitutively expressed in the nuclei of all seven of the HTLV-I-infected cell lines, even in the absence of detectable Tax or other viral gene expression. These findings raise the possibility of an alternate, Tax-independent pathway for the induced nuclear expression of NF-kappa B p50 and NF-kappa B p65 following HTLV-I infection.
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PMID:Human T-cell leukemia virus type I Tax induces expression of the Rel-related family of kappa B enhancer-binding proteins: evidence for a pretranslational component of regulation. 171 36

The NF-kappa B transcription factor complex is composed of two proteins, designated p50 and p65, both having considerable homology to the product of the rel oncogene. We present evidence that the p65 subunit is a potent transcriptional activator in the apparent absence of the p50 subunit, consistent with in vitro results demonstrating that p65 can interact with DNA on its own. To identify the minimal activation domain, chimeric fusion proteins between the DNA binding domain of the yeast transcriptional activator protein GAL4 and regions of the carboxy terminus of p65 were constructed, and their transcriptional activity was assessed by using a GAL4 upstream activation sequence-driven promoter-chloramphenicol acetyltransferase fusion. This analysis suggests that the boundaries of the activation domain lie between amino acids 415 and 550. Moreover, single amino acid changes within residues 435 to 459 greatly diminished activation. Similar to other activation domains, this region contains a leucine zipper-like motif as well as an overall net negative charge. To identify those residues essential for DNA binding, we made use of a naturally occurring derivative of p65, lacking residues 222 to 231 (hereafter referred to as p65 delta), and produced via an alternative splice site. Gel mobility shift analysis using bacterially expressed p65, p65 delta, and various mutants indicates that residues 222 to 231 are important for binding to kappa B DNA. Coimmunoprecipitation analysis suggests that these residues likely contribute to the multimerization function required for homomeric complex formation or heteromeric complex formation with p50 in that no association of p65 delta with itself or with p50 was evident. However, p65 delta was able to form weak heteromeric complexes with p65 that were greatly reduced in their ability to bind DNA. On the basis of these findings, we suggest that subtle changes within the proposed multimerization domain can elicit different effects with the individual Rel-related proteins and that a potential role of p65 delta may be to negatively regulate NF-kappa B function through formation of nonfunctional heteromeric complexes.
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PMID:Functional characterization of the NF-kappa B p65 transcriptional activator and an alternatively spliced derivative. 173 26

Transcription of the vascular cell adhesion molecule 1 (VCAM-1) gene in endothelial cells is induced by lipopolysaccharide and the inflammatory cytokines interleukin-1 beta and tumor necrosis factor alpha (TNF-alpha). Previous studies have demonstrated that tandem binding sites for the inducible transcription factor NF-kappa B are necessary but not sufficient for full cytokine-mediated transcriptional activation. Herein, we demonstrate that full cytokine-induced accumulation of VCAM1 transcript requires protein synthesis. We report the definition of a functional regulatory element in the VCAM1 promoter interacting with the transcriptional activator interferon regulatory factor 1 (IRF-1). DNA-protein binding studies with endothelial nuclear extracts revealed that IRF-1 is cytokine inducible and binds specifically to a consensus sequence motif located 3' of the TATA element. We have identified heterodimeric p65 and p50 as the NF-kappa B species binding to the VCAM1 promoter in TNF-alpha-activated endothelial cells. Experiments with recombinant proteins showed that p50/p65 and high-mobility-group I(Y) protein cooperatively facilitated the binding of IRF-1 to the VCAM1 IRF binding site and that IRF-1 physically interacted with p50 and with high-mobility-group I(Y) protein. Transient transfection assay in endothelial cells showed that overexpressed IRF-1 resulted in superinduction of TNF-alpha-stimulated transcription. Site-directed mutations in the IRF binding element decreased TNF-alpha-induced activity and totally abolished superinduction. Cotransfection assays in P19 embryonal carcinoma cells revealed that IRF-1 synergized with p50/p65 NF-kappa B to activate the VCAM1 promoter or heterologous promoter constructs bearing isolated VCAM1 NF-kappa B and IRF binding motifs. Cytokine inducibility of VCAM1 in endothelial cells utilizes the interaction of heterodimeric p50/p65 proteins with IRF-1.
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PMID:Endothelial interferon regulatory factor 1 cooperates with NF-kappa B as a transcriptional activator of vascular cell adhesion molecule 1. 753 51

T-cell activation requires two different signals. The T-cell receptor's recognition of a specific antigen on antigen-presenting cells provides one, and the second signal comes from costimulatory molecules such as CD28. In contrast, T cells that are stimulated with antigen in the absence of the CD28 costimulatory signal can become anergic (nonresponsive). The CD28 response element (CD28RE) has been identified as the DNA element mediating interleukin 2 (IL-2) gene activation by CD28 costimulation. Our previous work demonstrates that the Rel/NF-kappa B family proteins c-Rel, RelA (p65), and NFKB1 (p50) are involved in the complex that binds to the CD28RE. We also showed that c-Rel, but not NFKB1 (p50), can bind to the CD28RE and activate CD28RE-driven transcription in cotransfection assays. However, the role of RelA (p65) in CD28 signaling has not yet been addressed. We provide evidence that RelA (p65) itself bound directly to the CD28RE of the IL-2 promoter and other lymphokine promoters. In addition, RelA (p65) was a potent transcriptional activator of the CD28RE in vivo. We show that a RelA (p65)-c-Rel heterodimer bound to the CD28RE and synergistically activated the CD28RE enhancer activity. We also demonstrate that activated Raf-1 kinase synergized with RelA (p65) in activating the CD28RE enhancer activity. Interestingly, a soluble anti-CD28 monoclonal antibody alone, in the absence of other stimuli, also synergized with RelA (p65) in activating the CD28RE. Furthermore, we show that RelA (p65) activated expression of the wild-type IL-2 promoter but not the CD28RE-mutated IL-2 promoter. A combination of RelA (p65) and NFKB1 (p50) also activated the IL-2 promoter through the CD28RE site. These results demonstrate the functional regulation of the CD28RE, within the IL-2 promoter, by Rel/NF-kappa B transcription factors.
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PMID:RelA is a potent transcriptional activator of the CD28 response element within the interleukin 2 promoter. 762 20

The tax gene product of human T-cell leukemia virus type I (HTLV-I) is a potent transcriptional activator that both stimulates viral gene expression and activates an array of cellular genes involved in T-cell growth. Tax acts indirectly by inducing or modifying the action of various host transcription factors, including members of the NF-kappa B/Rel family of enhancer-binding proteins. In resting T cells, many of these NF-kappa B/Rel factors are sequestered in the cytoplasm by various ankyrin-rich inhibitory proteins, including I kappa B alpha. HTLV-I Tax expression leads to the constitutive nuclear expression of biologically active NF-kappa B and c-Rel complexes; however, the biochemical mechanism(s) underlying this response remains poorly understood. In this study, we demonstrate that Tax-stimulated nuclear expression of NF-kappa B in both HTLV-I-infected and Tax-transfected human T cells is associated with the phosphorylation and rapid proteolytic degradation of I kappa B alpha. In contrast to prior in vitro studies, at least a fraction of the phosphorylated form of I kappa B alpha remains physically associated with the NF-kappa B complex in vivo but is subject to rapid degradation, thereby promoting the nuclear translocation of the active NF-kappa B complex. We further demonstrate that Tax induction of nuclear c-Rel expression is activated by the RelA (p65) subunit of NF-kappa B, which activates transcription of the c-rel gene through an intrinsic kappa B enhancer element. In normal cells, the subsequent accumulation of nuclear c-Rel acts to inhibit its own continued production, indicating the presence of an autoregulatory loop. However, the pathologic action HTLV-I Tax leads to the deregulated and sustained nuclear expression of both NF-kappa B and c-Rel, a response that may contribute to HTLV-I-induced T-cell transformation.
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PMID:Human T-cell leukemia virus type I Tax activation of NF-kappa B/Rel involves phosphorylation and degradation of I kappa B alpha and RelA (p65)-mediated induction of the c-rel gene. 793 51

The tumor suppressor p53 is a potent transcriptional activator that has been shown to regulate its own expression. In earlier studies, deletion analysis and site-specific mutagenesis identified the p53-responsive element that fits the p53 consensus sequence. In addition, the p53-responsive element was predicted to be a binding site for NF-kappa B. In this study, we showed that NF-kappa B present in HeLa nuclear extracts could bind the same DNA element in a sequence-specific manner. Co-transfection experiments showed that the p65 subunit of NF-kappa B, but not the p50 subunit, could activate the p53 promoter. In HeLa cells, tumor necrosis factor alpha (TNF-alpha) induced NF-kappa B activity. The p53 promoter was also induced by TNF-alpha under the same conditions. Both p65 transactivation and TNF-alpha induction of the p53 promoter depended on an intact NF-kappa B site. Detailed mutational analysis of the p53 and NF-kappa B responsive elements allowed differentiation of these two responses. Thus, we show that NF-kappa B activates p53 and that this activation is inducible by TNF-alpha. Since NF-kappa B induction occurs as a response to stress and p53 arrests cells in G1/S, where repair may be initiated, activation of p53 by NF-kappa B could be a mechanism by which cells can recover from stress.
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PMID:NF-kappa B activation of p53. A potential mechanism for suppressing cell growth in response to stress. 805 Oct 93

HeLa cells contain a DNA-binding activity which associates with a kappa B-like DNA element, termed Rel-related protein-binding element (RRBE), localized upstream of the human urokinase promoter. We have purified this activity from the HeLa cell cytosol and have shown that it represents a performed heteromeric complex between p65 (RelA) and c-Rel. Coexpression of c-Rel and p65 (RelA) by in vitro translation formed a DNA-binding complex indistinguishable from purified cellular c-Rel-p65 (RelA) in mobility shift assays. The c-Rel-p65 (RelA) complex was also formed in COS7 cells upon coexpression of c-Rel and p65 (RelA) cDNAs. Cotransfection experiments with COS7 cells, using expression plasmids encoding p50, p65 (RelA), or c-Rel and reporter constructs containing a trimerized RRBE, revealed that c-Rel-p65 (RelA) is a potent activator of the RRBE, giving rise to transcriptional activity higher than that observed with NF-kappa B (p50-p65). In the cytosol, the c-Rel-p65 (RelA) complex existed in a latent, non-DNA-binding form but could be activated by detergent treatment, suggesting that it was associated with an I kappa B protein. Recombinant I kappa B-alpha inhibited the DNA-binding activity of c-Rel-p65 (RelA) via association with either c-Rel or p65 (RelA). Finally, NF-kappa B and c-Rel-p65 (RelA) complexes were found to be differentially expressed and regulated in different cells. The two complexes were present in equimolar amounts in HeLa cells and K562 cells. Stimulation with tetradecanoyl phorbol acetate (TPA) resulted in the nuclear translocation of both NF-kappa B and c-Rel-p65 (RelA) in HeLa cells and of NF-kappa B in HepG2 cells but had no effect on either complex in K562 cells. In addition, TPA stimulation of HepG2 cells induced the expression of a cytosolic latent c-Rel-p65 (RelA) complex which, however, was not translocated to the nucleus. In conclusion, our findings show that c-Rel-p65 (RelA) is an inducible and very potent transcriptional activator which is differentially activated in a cell-type-specific manner.
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PMID:Purification, reconstitution, and I kappa B association of the c-Rel-p65 (RelA) complex, a strong activator of transcription. 813 61

NF-kappa B is a rapidly inducible transcriptional activator that responds to a variety of signals and influences the expression of many genes involved in the immune response. Protein tyrosine kinases transmit signals from cytokine and immune receptors. Very little information exists linking these two important classes of signaling molecules. We now demonstrate that v-src expression correlates with nuclear expression of a kappa B binding complex similar to that induced by phorbol ester and ionomycin, as detected by electrophoretic mobility shift assay using a variety of kappa B sites. This complex was blocked by the tyrosine kinase inhibitor, herbimycin A. The v-src-induced complex comprised the p50 and p65 components of NF-kappa B, as determined by supershift and immunoblot analysis. As a functional correlate of this finding, transient co-transfection of HIV-1 LTR reporter constructs in a different T cell line demonstrated that v-src activated this promoter in a kappa B-dependent manner. We found that transactivation of the HIV-1 LTR by v-src was more sensitive to mutations of the proximal, rather than the distal, kappa B element. The implications for T cell receptor signaling and HIV-1 gene expression are considered.
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PMID:Expression of v-src in T cells correlates with nuclear expression of NF-kappa B. 814 78

The correlation between virus induced NF-kappa B DNA binding activity and interferon gene expression was examined in the myelomonoblastic PLB-985 cell line. Previous studies have shown that chronic HIV-1 infection of PLB-985 cells (PLB-IIIB) leads to the selection of cells with a more differentiated monocytic phenotype and with constitutive NF-kappa B DNA-binding activity. In this report we demonstrate that the kinetics of HIV-1 and Sendai virus infection of PLB-985 cells directly correlates with induction of NF-kappa B DNA binding activity. Based on UV cross-linking and immunoprecipitation analysis, p50, the strong transcriptional activator p65 and c-Rel represent the major constituents of this NF-kappa B DNA-binding activity. We also demonstrate an alteration in the kinetics of type I IFN gene transcription following secondary Sendai virus infection of PLB-IIIB cells compared to PLB-985. The results of our studies suggest that HIV infected individuals may respond differently to secondary viral or bacterial infections by augmenting the synthesis of NF-kappa B regulated immune response modifiers, which could alter the onset or progression of AIDS.
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PMID:Virus induction of NF-kappa B/Rel proteins and type I interferon gene expression in myelomonoblastic cells. 815 86

The murine c-myc gene contains two elements responsive to the rel-oncogene-related family of NF-kappa B factors. Previously we have shown that factor binding to these two NF-kappa B elements mediates induction of transcription of the c-myc promoter upon interleukin-1 treatment of human dermal fibroblasts and human T-cell leukemia virus type I tax gene expression in T cells (D. J. Kessler, M. P. Duyao, D. B. Spicer, and G. E. Sonenshein, J. Exp. Med. 176:787-792, 1992; M. P. Duyao, D. J. Kessler, D. B. Spicer, C. Bartholomew, J. L. Cleveland, M. Siekevitz, and G. E. Sonenshein, J. Biol. Chem. 267:16288-16291, 1992). To begin to delineate the specific roles of the individual members of the NF-kappa B family, here we have tested their effects on activation of a c-myc promoter/exon 1-CAT construct in NIH 3T3 cells. Classical NF-kappa B (p65/p50) was a potent transcriptional activator of the c-myc promoter. Cotransfection with either p65 alone or p65 in combination with p50 mediated significant induction. In contrast, expression of either v-rel or chicken c-rel failed to transactivate, while murine c-rel induced c-myc promoter activity only slightly. Furthermore, induction by classical NF-kappa B was inhibited by coexpression of either v-rel or chicken c-rel. Thus, individual members of the rel family have differential effects of the c-myc promoter, which can modulate overall transcriptional activity and allow for precise regulation of this oncogene under diverse physiologic conditions.
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PMID:Differential regulation of the c-myc oncogene promoter by the NF-kappa B rel family of transcription factors. 828 84


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