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Query: UNIPROT:P05231 (interleukin-6)
 23,907 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During an acute phase response following inflammatory stimuli, specific changes occur in the synthesis and secretion of many hepatic proteins. Because the expression of differentiated function requires the coordinated regulation of many genes, we investigated the activity of general and tissue-specific transcription factors using a rat liver model of the acute phase response induced by Freund's adjuvant. Nuclear extracts and RNAs were prepared throughout a 48-h posttreatment period. Mobility shift assays revealed increased binding activity by nuclear factor-kappa B, interleukin-6 (IL-6) responsive element binding protein, and activating protein 1 (AP-1). Two AP-1 complexes were induced during the acute phase response, and correlation between their presence and transcription activity was demonstrated by transfection studies. Elevated binding activity of AP-1 also correlated with elevated levels of c-jun, junD, junB, and c-fos mRNAs. Western blots showed elevated hepatic levels of c-Jun but not c-Fos proteins during the acute phase response. In addition, IL-6, tumor necrosis factor-alpha, and IL-1 beta, cytokine regulators of the acute phase response, stimulated expression of an AP-1 responsive reporter gene introduced by DNA-mediated transfection into adult rat hepatocytes in primary culture. These findings demonstrate the complexity of AP-1 hepatic transcription factor responses to humoral regulators with direct hepatocellular effects.
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PMID:Activation of activating protein 1 during hepatic acute phase response. 843 Aug 10

The immediate early gene, junB, is induced by interleukin-6 (IL-6) in plasmacytomas. In order to identify enhancers that mediate this effect, we cloned upstream and downstream sequences flanking the gene into a luciferase reporter gene vector containing the junB promoter and evaluated the IL-6 inducibility of these sequences by transient expression in an IL-6-dependent plasmacytoma cell line. Although a 6.5-kilobase fragment of upstream flanking sequence did not increase the IL-6 inducibility of the junB promoter, a 222-base pair fragment was identified in 2.1 kilobases of down-stream flanking sequence that both up-regulates the promoter and confers inducibility by IL-6. Point mutation of an acute phase response factor (APRF) site within this region significantly reduced up-regulation of the promoter in cells grown continuously in IL-6, as well as inducibility upon restimulation of cells with IL-6 after withdrawal from the growth factor. Point mutation of an NF-kappa B site sharing five nucleotides with the APRF site reduced up-regulation of the promoter but not inducibility by IL-6, whereas mutation of two other NF-kappa B sites in the 222-base pair fragment had no effect on expression. Western blotting of nuclear proteins purified by DNA affinity chromatography revealed inducible binding of Stat3 and constitutive binding of NF-kappa B p65 to the APRF/NF-kappa B site.
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PMID:An acute phase response factor/NF-kappa B site downstream of the junB gene that mediates responsiveness to interleukin-6 in a murine plasmacytoma. 853 75

Interleukin-6 (IL-6) induces growth arrest and macrophage differentiation through its receptor in a murine myeloid leukaemic cell line, M1, although it is largely unknown how the IL-6 receptor generates these signals. By using chimeric receptors consisting of the extracellular domain of growth hormone receptor and the transmembrane and cytoplasmic domain of gp130 with progressive C-terminal truncations, we showed that the membrane-proximal 133, but not 108, amino acids of gp130 could generate the signals for growth arrest, macrophage differentiation, down-regulation of c-myc and c-myb, induction of junB and IRF1 and Stat3 activation. Mutational analysis of this region showed that the tyrosine residue with the YXXQ motif was critical not only for Stat3 activation but also for growth arrest and differentiation, accompanied by down-regulation of c-myc and c-myb and immediate early induction of junB and IRF1. The tight correlation between Stat3 activation and other IL-6 functions was further observed in the context of the full-length cytoplasmic region of gp130. The result suggest that Stat3 plays an essential role in the signals for growth arrest and differentiation.
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PMID:Differentiation and growth arrest signals are generated through the cytoplasmic region of gp130 that is essential for Stat3 activation. 861 79

The junB gene is one of immediate-early genes whose expression are regulated by a variety of extracellular stimuli and play important roles in cellular responses to the given stimuli. Interleukin-6 (IL-6) activates the junB promoter through an IL-6 response element, JRE-IL6, that is composed of two cooperative DNA motifs, a low affinity Stat-binding site overlapping with an Ets-binding site (JEBS) and a cAMP responsive element (CRE)-like site. This element is a target for the Jak-Stat signal transduction pathway. We showed that IL-6 induced novel complexes on JRE-IL6, termed JRE-IL6-BC1 and 2, which contained Stat3 but migrated more slowly than the complexes containing homo- or heterodimer of Stat3 and Stat1 in gel shift assays. These slow-migrating JRE-IL6-BCs appeared to contain CRE-like site binding proteins besides Stat3, since the formation of JRE-IL6-BCs required both the JEBS and CRE-like site of JRE-IL6 and oligonucleotides containing the CRE-like site or somatostatin CRE efficiently competed with JRE-IL6 for making JRE-IL6-BCs. The formation of the complexes correlated well with the responsiveness of JRE-IL6 to IL-6 signals. U.v.-cross linking study revealed that JRE-IL6 bound a 90 kDa protein, corresponding to Stat3, and a 36 kDa protein, most likely a CRE-like site binding protein(s). Furthermore, we showed that the IL-6/interferon gamma (IFN gamma) response element in the IRF-1 promoter (IR/IRF-1), which contains a Stat-binding site and an adjacent CRE-like site, also makes IL-6-induced binding complexes similar to JRE-IL6-BCs.
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PMID:IL-6-inducible complexes on an IL-6 response element of the junB promoter contain Stat3 and 36 kDa CRE-like site binding protein(s). 863 11

The immediate early genes are regulated by a variety of extracellular signals, including pleiotropic cytokines. The effects of the testicular cytokines, interleukin-6 (IL-6) and interferon-gamma (IFN-gamma), on signal transducers and activators of transcription 3 and 1 (STAT-3 and STAT-1) and on c-fos gene expression in primary Sertoli cells are suggestive of their roles in differential function. Using the tyrosine phosphorylation inhibitor, genistein, and electrophoretic mobility shift assay, we show that IL-6 and IFN-gamma induce nuclear factor STAT-3 and STAT-1 DNA-binding activity to the sis-inducible element of c-fos in a genistein-dependent pathway. Quantitative solution hybridization, Northern blot, and nuclear run-on analysis show that differential induction of c-fos, junB, and c-myc messenger RNA (mRNA) by these cytokines occur at transcriptional levels. IL-6 stimulates c-fos mRNA levels by 6-fold while increasing junB levels by 2-fold. IFN-gamma increases c-fos message 2-fold, but has no effect on junB mRNA levels. Furthermore, genistein treatment blocks the induction of c-fos and junB gene expression, demonstrating that tyrosine phosphorylation of STAT proteins is involved in the cytokine regulation of the Sertoli immediate early genes. H7, a serine/threonine phosphorylation inhibitor, also blocks c-fos gene induction by IL-6 and IFN-gamma, but does not affect the DNA-binding activities of STAT-3 and STAT-1. Finally, IL-6 treatment of Sertoli cells (3-6 h) increases the amounts of activating protein-1 binding to activating protein-1 element and c-myc transcription.
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PMID:Transcriptional regulation of Sertoli cell immediate early genes by interleukin-6 and interferon-gamma is mediated through phosphorylation of STAT-3 and STAT-1 proteins. 920 12

Activation of the N-myc2 oncogene by integration of woodchuck hepatitis virus (WHV) DNA is a central event in woodchuck liver oncogenesis. In this study, we have evaluated the influence of several cellular and viral trans-acting factors and mediators of inflammation on N-myc2 promoter activity in hepatoma cell lines. Ets oncoproteins, including Ets1, Ets2 and PEA3 efficiently activated a chimeric N-myc2 promoter/luciferase reporter gene. By electrophoretic mobility shift assays, we show that Etsl and Ets2 proteins can efficiently bind two consensus Ets sites located within a 59 bp sequence upstream of the N-myc2 transcription start site. Site-directed mutagenesis of these Ets-binding motifs abolished transactivation of the N-myc2 promoter by Ets proteins. Addition of interleukin-6 (IL-6) induced a weak but reproducible activation of the N-myc2 promoter, while IL-1 was ineffective. We further show that the N-myc2 promoter can be transactivated by the hepadna-virus X protein, and that distal promoter sequences are required for both IL-6 and X responsiveness. Similar effects of these factors were observed in the context of the N-myc2 promoter activated by WHV cis-regulatory elements. In view of the high-level expression of the N-myc2 oncogene in most woodchuck liver tumors, the Ets oncoproteins, inflammation-associated cytokine IL-6 and the viral X transactivator might play important roles in hepadnavirus-associated tumorigenesis.
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PMID:Cellular and viral trans-acting factors modulate N-myc2 promoter activity in woodchuck liver tumors. 928 65

STAT3 (signal transducer and activator of transcription 3) is a key transcription factor mediating the signals for a variety of cytokines, including interleukin-6 (IL-6). The Stat3 gene itself is activated by IL-6 signals. We show that the region of the signal-transducing subunit, gp130, essential for STAT3 activation, is also required for activation of the Stat3 gene. To elucidate the mechanisms activating the Stat3 gene, we identified an IL-6 response element (IL-6RE) in the Stat3 gene promoter containing both a low affinity STAT3-binding element and a cAMP-responsive element (CRE). Electrophoretic mobility shift assays showed that IL-6 induced a slowly migrating complex on the IL-6RE containing a STAT3 homodimer and an unidentified CRE-binding protein. With the combination of transient transfection assays using mutant Stat3 promoter-reporter constructs and electrophoretic mobility shift assays, we found that the formation of a slowly migrating complex was required for full activation of the Stat3 gene. Thus, STAT3 activates the Stat3 gene in cooperation with an unidentified CRE-binding protein. This regulatory mechanism is similar to that of the junB gene, which is activated by IL-6 through the junB IL-6RE, which contains a low affinity STAT3-binding site and a CRE-like site.
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PMID:Autoregulation of the Stat3 gene through cooperation with a cAMP-responsive element-binding protein. 949 31

The transcription factor junB belongs to the jun family of protooncogenes. The appearance of junB mRNA in hepatic cells is an extremely early and sensitive marker of the action of proinflammatory cytokines including interleukin-6. In this study, a competitive reverse transcription (RT)-PCR assay has been developed that is suitable for the quantitative determination of junB mRNA expression. This nonisotopic assay compared to other methods (e.g., Northern blot) is a fast and convenient way to determine the expression of the junB gene and thus the immediate concentration- and time-dependent action of interleukin-6. Because interleukin-6 and interleukin-6-type cytokines play a highly important regulatory role in various pathophysiologically important processes, such as hepatic acute-phase reaction, the quantitative assay of junB mRNA completes the scale of laboratory approaches in inflammation and among other pathological conditions.
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PMID:Development of competitive mRNA PCR for the quantification of interleukin-6-responsive junB oncogene expression. 959 Nov 38

Interleukin-6 is a multifunctional cytokine participating in the regulation of several immunologic and other cell-physiological phenomena. It acts via a receptor consisting of two components, that besides the ligand-specific chain also contains a second component of 130 kD (gp 130). The soluble form of the ligand-specific component of this receptor was shown to occur physiologically in body fluids and -following the binding of interleukin-6-to be capable of associating with the membrane-bound receptor component and inducing signal-transduction. We studied the possible differences between the effects of interleukin-6 exerted via membrane-bound or soluble receptors on HepG2 human hepatoma and primary rat hepatocyte cultures. We used two methods to study the action of interleukin-6: the mRNA expression of the protooncogene junB as an early marker, and the protein production of fibrinogen as a late one. The effect of interleukin-6 on both cell types examined with both methods used was lower via the soluble than the membrane-bound receptor. In addition, the soluble receptors alone (without interleukin-6) could induce the expression of the junB gene. Considering the wide-spread biological and pathological activities of interleukin-6 these phenomena could have some role in the pathogenesis of some diseases.
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PMID:[Interleukin-6 acts in different ways via soluble and membrane-bound receptors]. 971 90

Cytokines and steroid hormones use different sets of signal transduction pathways, which seem to be unrelated. Interleukin-6 (IL-6) uses JAK tyrosine kinase and STAT (signal transducer and activator of transcription) transcription factor. Glucocorticoid binds glucocorticoid receptor (GR), which is a member of the steroid receptor superfamily. We have studied the crosstalk between the IL-6-JAK-STAT and glucocorticoid-nuclear receptor pathways. IL-6 and glucocorticoid synergistically activated the IL-6 response element on the rat alpha2-macroglobulin promoter (APRE)-driven luciferase gene. The exogenous expression of GR enhanced the synergism. The exogenous expression of dominant negative STAT3 completely abolished the IL-6 plus glucocorticoid-induced activation of the APRE-luciferase gene. Tyrosine phosphorylation of STAT3 stimulated by IL-6 alone was not different from that by IL-6 plus glucocorticoid. The protein level of STAT3 was also not increased by glucocorticoid stimulation. The time course of STAT3 tyrosine phosphorylation by IL-6 plus glucocorticoid was not different from that by IL-6 alone. The synergism was studied on the two other IL-6 response elements, the junB promoter (JRE-IL-6) and the interferon regulatory factor-1 (IRF-1) promoter (IRF-GAS) which could be activated by STAT3. The synergistic activation by glucocorticoid on the IL-6-activated JRE-IL-6 and the IRF-GAS-driven luciferase gene was not detected. Glucocorticoid did not change the mobility of IL-6-induced APRE-binding proteins in a gel shift assay. These results suggest that the synergism was through the GR and STAT3, and the coactivation pathway which was specific for APRE was the target of glucocorticoid.
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PMID:Crosstalk between the interleukin-6 (IL-6)-JAK-STAT and the glucocorticoid-nuclear receptor pathway: synergistic activation of IL-6 response element by IL-6 and glucocorticoid. 979 74


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