Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Menadione (vitamin K-3,2-methyl-1,4-naphthoquinone), a redox cycling reagent, generates reactive oxygen intermediates and causes oxidative injury. The addition of menadione to Hep G2 cells produced a time- and concentration-dependent loss of cell viability. Preincubation of Hep G2 cells with low, nontoxic concentrations of menadione increased the viability of the cells against toxic doses of menadione or H2O2. Maximum protection was found with menadione concentrations of approximately 3 microM and preincubation times of approximately 45 min. This protective effect could be blocked by the protein synthesis inhibitor cycloheximide and by a variety of antioxidants. The transcription factor nuclear factor-kappaF (NF-kappaB) is known to be activated by many compounds, including reactive oxygen intermediates. Menadione activated NF-kappaB as determined by electrophoretic mobility shift assays. This activation was prevented by the same antioxidants that blocked protection against cytotoxicity produced by preincubation with menadione. Anti-p50 IgG prevented the menadione-stimulated binding of NF-kappaB to the oligonucleotide probe, whereas anti-p65 IgG produced a supershift of the NF-kappaB/oligonucleotide complex. Salicylate prevented the activation of NF-kappaB by menadione, and under these conditions, salicylate potentiated the cytotoxicity of menadione or H2O2. Transfection with a plasmid containing cDNA encoding mouse IkappaBbeta, an inhibitor of NF-kappaB, resulted in increased toxicity by menadione. Furthermore, when protein kinase C was down-regulated by prolonged treatment with active phorbol ester (phorbol-12-myristate-13-acetate), the Hep G2 cells became more sensitive to menadione treatment. However, short term treatment with PMA, which activated NF-kappaB, resulted in protection against menadione cytotoxicity. Menadione cytotoxicity was enhanced when the Hep G2 cells were depleted of GSH. An increased level of GSH was observed after menadione pretreatment; this increase was blocked by salicylate, thereby linking the GSH increase to activation of NF-kappaB by menadione. The results of the current study suggest that menadione pretreatment protects Hep G2 cells from oxidative injury through an NF-kappaB-related mechanism, which may involve, in part, increased production of GSH.
Mol Pharmacol 1997 Oct
PMID:Menadione cytotoxicity to Hep G2 cells and protection by activation of nuclear factor-kappaB. 938 28

The Rel/NF-kappaB family of transcription factors is sequestered in the cytoplasm of most mammalian cells by inhibitor proteins belonging to the IkappaB family. Degradation of IkappaB by a phosphorylation-dependent ubiquitin-proteasome (inducible) pathway is believed to allow nuclear transport of active Rel/NF-kappaB dimers. Rel/NF-kappaB (a p50-c-Rel dimer) is constitutively nuclear in murine B cells, such as WEHI231 cells. In these cells, p50, c-Rel, and IkappaB alpha are synthesized at high levels but only IkappaB alpha is rapidly degraded. We have examined the mechanism of IkappaB alpha degradation and its relation to constitutive p50-c-Rel activation. We demonstrate that all IkappaB alpha is found complexed with c-Rel protein in the cytoplasm. Additionally, rapid IkappaB alpha proteolysis is independent of but coexistent with the inducible pathway and can be inhibited by calcium chelators and some calpain inhibitors. Conditions that prevent degradation of IkappaB alpha also inhibit nuclear p50-c-Rel activity. Furthermore, the half-life of nuclear c-Rel is much shorter than that of the cytoplasmic form, underscoring the necessity for its continuous nuclear transport to maintain constitutive p50-c-Rel activity. We observed that IkappaB beta, another NF-kappaB inhibitor, is also complexed with c-Rel but slowly degraded by a proteasome-dependent process in WEHI231 cells. In addition, IkappaB beta is basally phosphorylated and cytoplasmic. We thus suggest that calcium-dependent IkappaB alpha proteolysis maintains nuclear transport of a p50-c-Rel heterodimer which in turn activates the synthesis of IkappaB alpha, p50, and c-Rel to sustain this dynamic process in WEHI231 B cells.
Mol Cell Biol 1998 Jan
PMID:Novel IkappaB alpha proteolytic pathway in WEHI231 immature B cells. 941 49

Transforming growth factor beta (TGF-beta) is the prototype of a large superfamily of signaling molecules involved in the regulation of cell growth and differentiation. In certain patients infected with human immunodeficiency virus type 1 (HIV-1), increased levels of TGF-beta promoted the production of virus and also impaired the host immune system. In an effort to understand the signaling events linking TGF-beta action and HIV production, we show here that TGF-beta can stimulate transcription from the HIV-1 long terminal repeat (LTR) promoter through NF-kappaB binding sites in both HaCaT and 300.19 pre-B cells. When introduced into a minimal promoter, NF-kappaB binding sites supported nearly 30-fold activation from the luciferase reporter upon TGF-beta treatment. Electrophoretic mobility shift assay indicated that a major factor binding to the NF-kappaB site is the p50-p65 heterodimeric NF-kappaB in HaCaT cells. Coexpression of Gal4-p65 chimeric proteins supported TGF-beta ligand-dependent gene expression from a luciferase reporter gene driven by Gal4 DNA binding sites. NF-kappaB activity present in HaCaT cells was not affected by TGF-beta treatment as judged by the unchanged DNA binding activity and concentrations of p50 and p65 proteins. Consistently, steady-state levels of IkappaB alpha and IkappaB beta proteins were not changed by TGF-beta treatment. Our results demonstrate that TGF-beta is able to stimulate transcription from the HIV-1 LTR promoter by activating NF-kappaB through a mechanism distinct from the classic NF-kappaB activation mechanism involving the degradation of IkappaB proteins.
Mol Cell Biol 1998 Jan
PMID:Transforming growth factor beta stimulates the human immunodeficiency virus 1 enhancer and requires NF-kappaB activity. 941 59

High concentrations of iodide can induce transient, clinical improvement in patients with autoimmune Graves' disease. Previous work has related this iodide action to the autoregulatory effect of iodide on the growth and function of the thyroid; more recently, we additionally related this to the ability of iodide to suppress major histocompatibility (MHC) class I RNA levels and antigen expression on thyrocytes. In this report, we describe a transcriptional mechanism involved in iodide suppression of class I gene expression, which is potentially relevant to the autoregulatory action of iodide. Transfection experiments in FRTL-5 cells show that iodide decreases class I promoter activity and that this effect can be ascribed to the ability of iodide to modulate the formation of two specific protein/DNA complexes with enhancer A, -180 to -170 bp, of the class 1 5'-flanking region. Thus, iodide decreases the formation of Mod-1, an enhancer A complex involving the p50 subunit of NF-kappa B and a c-fos family member, fra-2, which was previously shown to be important in the suppression of class I levels by hydrocortisone. Unlike hydrocortisone, iodide also increases the formation of a complex with enhancer A, which we show, in antibody shift experiments, is a heterodimer of the p50 and p65 subunits of NF-kappa B. The changes in these complexes are not duplicated by chloride and are related to the action of iodide on class I RNA levels by the following observations. First, FRTL-5 thyroid cells with an aged phenotype coincidentally lose the ability of iodide to decrease MHC class I RNA levels and to induce changes in either complex. Second, the effect of iodide on class I RNA levels and on enhancer A complex formation with Mod-1 and the p50/p65 heterodimer is inhibited by agents that block the inositol phosphate, Ca++, phospholipase A2, arachidonate signal transduction pathway: acetylsalicylate, indomethacin, and 5,8,11,14-eicosatetraynoic acid. Interestingly, iodide can also decrease formation of the Mod-1 complex and increase formation of the complex with the p50/p65 subunits of NF-kappa B when the NF-kappa B enhancer sequence from the Ig kappa light chain, rather than enhancer A, is used as probe; and both actions mimic the action of a phorbol ester. This suggests that iodide may regulate complex formation with NF-kappa B regulatory elements on multiple genes associated with growth and function, providing a potential mechanism relating the autoregulatory action of iodide on thyroid cells and its action on class I gene expression.
Mol Endocrinol 1998 Jan
PMID:Iodide suppression of major histocompatibility class I gene expression in thyroid cells involves enhancer A and the transcription factor NF-kappa B. 944 Aug 7

Nuclear factor kappa B (NF-kappa B) is an inducible transcription factor that positively regulates the expression of proimmune and proinflammatory genes, while glucocorticoids are potent suppressors of immune and inflammatory responses. NF-kappa B and the glucocorticoid receptor (GR) physically interact, resulting in repression of NF-kappa B transactivation. In transient cotransfection experiments, we demonstrate a dose-dependent, mutual antagonism between NF-kappa B and GR. Functional dissection of the NF-kappa B p50 and p65 subunits and deletion mutants of GR indicate that the GR antagonism is specific to the p65 subunit of NF-kappa B heterodimer, whereas multiple domains of GR are essential to repress p65-mediated transactivation. Despite its repression of GR transactivation, p65 failed to block the transrepressive GR homologous down-regulation function. We also demonstrate that negative interactions between p65 and GR are not selective for GR, but also occur between NF-kappa B and androgen, progesterone B, and estrogen receptors. However, although each of these members of the steroid hormone receptor family is repressed by NF-kappa B, only GR effectively inhibits p65 transactivation. Further, in cotransfections using a chimeric estrogen-GR, the presence of the GR DNA-binding domain is insufficient to confer mutual antagonism to the p65-estrogen receptor interaction. Selectivity of p65 repression for each steroid receptor is demonstrated by I kappa B rescue from NF-kappa B-mediated inhibition. Together these data suggest that NF-kappa B p65 physically interacts with multiple steroid hormone receptors, and this interaction is sufficient to transrepress each steroid receptor. Further, the NF-kappa B status of a cell has the potential to significantly alter multiple steroid signaling pathways within that cell.
Mol Endocrinol 1998 Jan
PMID:Cross-talk between nuclear factor-kappa B and the steroid hormone receptors: mechanisms of mutual antagonism. 944 Aug 9

Gene activation by NF-kappaB/Rel transcription factors is modulated by synergistic or antagonistic interactions with other promoter-bound transcription factors. For example, Sp1 sites are often found in NF-kappaB-regulated genes, and Sp1 can activate certain promoters in synergism with NF-kappaB through nonoverlapping binding sites. Here we report that Sp1 acts directly through a subset of NF-kappaB binding sites. The DNA binding affinity of Sp1 to these NF-kappaB sites, as determined by their relative dissociation constants and their relative efficiencies as competitor DNAs or as binding site probes, is in the order of that for a consensus GC box Sp1 site. In contrast, NF-kappaB does not bind to a GC box Sp1 site. Sp1 can activate transcription through immunoglobulin kappa-chain enhancer or P-selectin promoter NF-kappaB sites. p50 homodimers replace Sp1 from the P-selectin promoter by binding site competition and thereby either inhibit basal Sp1-driven expression or, in concert with Bcl-3, stimulate expression. The interaction of Sp1 with NF-kappaB sites thus provides a means to keep an elevated basal expression of NF-kappaB-dependent genes in the absence of activated nuclear NF-kappaB/Rel.
Mol Cell Biol 1998 Mar
PMID:Functional interference of Sp1 and NF-kappaB through the same DNA binding site. 948 41

Members of the Rel/NF-kappaB family of transcription factors are related to each other over a region of about 300 amino acids called the Rel Homology Domain (RHD), which governs DNA binding, dimerization, and binding to inhibitor. At the C-terminal end of the RHD, each protein has a nuclear localization signal (NLS). The crystal structures of the p50 and RelA family members show that the RHD consists of two regions: an N-terminal section which contains some of the DNA contacts and a C-terminal section which contains the remaining DNA contacts and controls dimerization. In unstimulated cells, the homo- or heterodimeric Rel/NF-kappaB proteins are cytoplasmic by virtue of binding to an inhibitor protein (IkappaB) which somehow masks the NLS of each member of the dimer. The IkappaB proteins consist of an ankyrin-repeat-containing domain that is required for binding to dimers and N- and C-terminal domains that are dispensable for binding to most dimers. In this study, we examined the interaction between IkappaB alpha and Rel family homodimers by mutational analysis. We show that (i) the dimerization regions of p50, RelA, and c-Rel are sufficient for binding to IkappaB alpha, (ii) the NLSs of RelA and c-Rel are not required for binding to IkappaB alpha but do stabilize the interaction, (iii) the NLS of p50 is required for binding to IkappaB alpha, (iv) only certain residues within the p50 NLS are required for binding, and (v) in a p50-IkappaB alpha complex or a c-Rel-IkappaB alpha complex, the N terminus of IkappaB alpha either directly or indirectly masks one or both of the dimer NLSs.
Mol Cell Biol 1998 May
PMID:The N-terminal domain of IkappaB alpha masks the nuclear localization signal(s) of p50 and c-Rel homodimers. 956 83

The purified Rel/NF-kappaB (p50/p65) complex and Sp1 markedly activate transcription from the human immunodeficiency virus type 1 (HIV-1) promoter in a highly purified HeLa reconstituted transcription system. Transcriptional activation by NF-kappaB and Sp1 requires both TFIID and the USA fraction. The USA-derived coactivators PC2 and PC4 fully reconstitute the USA coactivator activity, both by repressing the basal level of transcription and by potentiating activator function to yield large increases in the levels of transcription induction. Under limiting concentrations, PC2 and PC4 also show synergistic effects. The C-terminal portion (amino acids 416 to 550) of the p65 subunit of NF-kappaB is a potent activator when assayed as a Gal fusion in the reconstituted transcription system and interacts both with TATA-binding protein (TBP) and with several human TBP-associated factors (TAFs) that include TAFII250. The p65 activation domain mediates transcription activation in the presence of partially reconstituted TFIID species that include a minimal complex containing only TBP and TAFII250. These studies also show that, like USA components, TAFs can serve both to repress TBP-mediated transcription and, following activator interactions, to reverse the repression and effect a net increase in activity. Taken together, these data underscore the importance of both TAFs and specific USA-derived coactivators for optimal activation of the HIV-1 promoter, as well as certain parallels in their overall mechanisms of action.
Mol Cell Biol 1998 Jun
PMID:Involvement of TFIID and USA components in transcriptional activation of the human immunodeficiency virus promoter by NF-kappaB and Sp1. 958 64

We examined activation of the transcription factor, nuclear factor-kappaB (NF-kappaB), which participates in the upregulation of endothelial cell adhesion proteins, during reperfusion after temporary middle cerebral artery occlusion (TMCAO). We hypothesized that N-acetylcysteine (NAC), an antioxidant which inhibits NF-kappaB activation, would alter events in brain reperfusion injury. We used a rat model of TMCAO. The left sides of the brains were rendered ischemic for 2 h, and then the area was allowed to reperfuse. The animals were treated with NAC (150 mg/kg) or saline placebo, sacrificed, and activated NF-kappaB was assessed in both the left and right hemispheres, all at varying intervals. Cerebral infarction volume was also measured in each of the hemispheres collected from a separate group of animals. Activated NF-kappaB, consisting of p65 and p50 Rel proteins, was significantly increased 15 min after reperfusion in the affected hemisphere. The activation at 15 min was completely abolished with NAC treatment. NAC treatment 1 h prior to the end of occlusion and at 24 h reduced the percentage infarction volume of the affected hemispheres from 35.5+/-2.8% (S.E.) to 18. 1+/-2.1% (p<0.01). NAC treatment at 1 h after the occlusion (after the NF-kappaB peak) and again at 24 h also significantly reduced the percentage infarction volume from 34.8+/-3.8% to 24.6+/-3.8% (p<0. 05). Thus, while NAC inhibited activation of NF-kappaB at 15 min after reperfusion, the drug acted to reduce cerebral infarction by additional, undefined mechanisms. These results bring into question the various roles of NF-kappaB in cerebral infarction followed by reperfusion.
Brain Res Mol Brain Res 1998 May
PMID:Nuclear factor-kappa B activation during cerebral reperfusion: effect of attenuation with N-acetylcysteine treatment. 960 21

1H and 31P NMR spectroscopy have been used together with molecular modelling to determine the fine structure of a non-palindromic 16 bp DNA containing the NF-kappa B binding site. Much emphasis has been placed upon NMR optimization of both two-dimensional 31P NMR techniques to extract structural information defining the phosphodiester backbone conformation and selective homonuclear 2D COSY experiments to determine sugar conformations. NMR data show evidence for a dynamic behaviour of steps flanking the ten base-pairs of the NF-kappa B binding site. A BI-BII equilibrium at these steps is demonstrated and two models for each extreme conformation are proposed in agreement with NMR data. In the refined BII structures, the NF-kappa B binding site exhibits an intrinsic curvature towards the major groove that is magnified by the four flanking steps in the BII conformation. Furthermore, the base-pairs are translated into the major groove. Thus, we present a novel mode of dynamic intrinsic curvature compatible with the DNA curvature observed in the X-ray structure of the p50-DNA complex.
J Mol Biol 1998 May 29
PMID:Solution structure of a non-palindromic 16 base-pair DNA related to the HIV-1 kappa B site: evidence for BI-BII equilibrium inducing a global dynamic curvature of the duplex. 963 5


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