scholarly journals Mutational analysis of acute-phase response factor/Stat3 activation and dimerization.

1997 ◽  
Vol 17 (8) ◽  
pp. 4677-4686 ◽  
Author(s):  
J Sasse ◽  
U Hemmann ◽  
C Schwartz ◽  
U Schniertshauer ◽  
B Heesel ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Acute Phase ◽  
Interleukin 6 ◽  
Acute Phase Response ◽  
Phase Response ◽  
Response Factor ◽  
Transactivation Domain ◽  
Signal Transducer ◽  
Amino Terminal ◽  
Carboxy Terminal

Signal transducer and transcription (STAT) factors are activated by tyrosine phosphorylation in response to a variety of cytokines, growth factors, and hormones. Tyrosine phosphorylation triggers dimerization and nuclear translocation of these transcription factors. In this study, the functional role of carboxy-terminal portions of the STAT family member acute-phase response factor/Stat3 in activation, dimerization, and transactivating potential was analyzed. We demonstrate that truncation of 55 carboxy-terminal amino acids causes constitutive activation of Stat3 in COS-7 cells, as is known for the Stat3 isoform Stat3beta. By the use of deletion and point mutants, it is shown that both carboxy- and amino-terminal portions of Stat3 are involved in this phenomenon. Dimerization of Stat3 was blocked by point mutations affecting residues both in the vicinity of the tyrosine phosphorylation site (Y705) and more distant from this site, suggesting that multiple interactions are involved in dimer formation. Furthermore, by reporter gene assays we demonstrate that carboxy-terminally truncated Stat3 proteins are incapable of transactivating an interleukin-6-responsive promoter in COS-7 cells. In HepG2 hepatoma cells, however, these truncated Stat3 forms transmit signals from the interleukin-6 signal transducer gp130 equally well as does full-length Stat3. We conclude that, dependent on the cell type, different mechanisms allow Stat3 to regulate target gene transcription either with or without involvement of its putative carboxy-terminal transactivation domain.

scholarly journals Differential Activation of Acute Phase Response Factor/STAT3 and STAT1 via the Cytoplasmic Domain of the Interleukin 6 Signal Transducer gp130

1996 ◽  
Vol 271 (22) ◽  
pp. 12991-12998 ◽  
Author(s):  
Claudia Gerhartz ◽  
Birgit Heesel ◽  
Jürgen Sasse ◽  
Ulrike Hemmann ◽  
Christiane Landgraf ◽  
...  
Keyword(s):  
Acute Phase ◽  
Interleukin 6 ◽  
Acute Phase Response ◽  
Cytoplasmic Domain ◽  
Phase Response ◽  
Response Factor ◽  
Signal Transducer ◽  
Differential Activation

scholarly journals Differential Activation of Acute Phase Response Factor/Stat3 and Stat1 via the Cytoplasmic Domain of the Interleukin 6 Signal Transducer gp130

1996 ◽  
Vol 271 (22) ◽  
pp. 12999-13007 ◽  
Author(s):  
Ulrike Hemmann ◽  
Claudia Gerhartz ◽  
Birgit Heesel ◽  
Jürgen Sasse ◽  
Günther Kurapkat ◽  
...  
Keyword(s):  
Acute Phase ◽  
Interleukin 6 ◽  
Acute Phase Response ◽  
Cytoplasmic Domain ◽  
Phase Response ◽  
Response Factor ◽  
Signal Transducer ◽  
Differential Activation

scholarly journals Acute-phase response factor, a nuclear factor binding to acute-phase response elements, is rapidly activated by interleukin-6 at the posttranslational level

1993 ◽  
Vol 13 (1) ◽  
pp. 276-288
Author(s):  
U M Wegenka ◽  
J Buschmann ◽  
C Lütticken ◽  
P C Heinrich ◽  
F Horn
Keyword(s):  
Transcriptional Regulation ◽  
Acute Phase ◽  
Interleukin 6 ◽  
Acute Phase Response ◽  
Acute Phase Protein ◽  
Phase Response ◽  
Response Factor ◽  
Nuclear Factor ◽  
Response Elements ◽  
Phase Protein

Interleukin-6 (IL-6) is known to be a major mediator of the acute-phase response in liver. We show here that IL-6 triggers the rapid activation of a nuclear factor, termed acute-phase response factor (APRF), both in rat liver in vivo and in human hepatoma (HepG2) cells in vitro. APRF bound to IL-6 response elements in the 5'-flanking regions of various acute-phase protein genes (e.g., the alpha 2-macroglobulin, fibrinogen, and alpha 1-acid glycoprotein genes). These elements contain a characteristic hexanucleotide motif, CTGGGA, known to be required for the IL-6 responsiveness of these genes. Analysis of the binding specificity of APRF revealed that it is different from NF-IL6 and NF-kappa B, transcription factors known to be regulated by cytokines and involved in the transcriptional regulation of acute-phase protein genes. In HepG2 cells, activation of APRF was observed within minutes after stimulation with IL-6 or leukemia-inhibitory factor and did not require ongoing protein synthesis. Therefore, a preexisting inactive form of APRF is activated by a posttranslational mechanism. We present evidence that this activation occurs in the cytoplasm and that a phosphorylation is involved. These results lead to the conclusions that APRF is an immediate target of the IL-6 signalling cascade and is likely to play a central role in the transcriptional regulation of many IL-6-induced genes.

scholarly journals Acute-phase response factor, a nuclear factor binding to acute-phase response elements, is rapidly activated by interleukin-6 at the posttranslational level.

1993 ◽  
Vol 13 (1) ◽  
pp. 276-288 ◽  
Author(s):  
U M Wegenka ◽  
J Buschmann ◽  
C Lütticken ◽  
P C Heinrich ◽  
F Horn
Keyword(s):  
Transcriptional Regulation ◽  
Acute Phase ◽  
Interleukin 6 ◽  
Acute Phase Response ◽  
Acute Phase Protein ◽  
Phase Response ◽  
Response Factor ◽  
Nuclear Factor ◽  
Response Elements ◽  
Phase Protein

Interleukin-6 (IL-6) is known to be a major mediator of the acute-phase response in liver. We show here that IL-6 triggers the rapid activation of a nuclear factor, termed acute-phase response factor (APRF), both in rat liver in vivo and in human hepatoma (HepG2) cells in vitro. APRF bound to IL-6 response elements in the 5'-flanking regions of various acute-phase protein genes (e.g., the alpha 2-macroglobulin, fibrinogen, and alpha 1-acid glycoprotein genes). These elements contain a characteristic hexanucleotide motif, CTGGGA, known to be required for the IL-6 responsiveness of these genes. Analysis of the binding specificity of APRF revealed that it is different from NF-IL6 and NF-kappa B, transcription factors known to be regulated by cytokines and involved in the transcriptional regulation of acute-phase protein genes. In HepG2 cells, activation of APRF was observed within minutes after stimulation with IL-6 or leukemia-inhibitory factor and did not require ongoing protein synthesis. Therefore, a preexisting inactive form of APRF is activated by a posttranslational mechanism. We present evidence that this activation occurs in the cytoplasm and that a phosphorylation is involved. These results lead to the conclusions that APRF is an immediate target of the IL-6 signalling cascade and is likely to play a central role in the transcriptional regulation of many IL-6-induced genes.

scholarly journals The interleukin-6-activated acute-phase response factor is antigenically and functionally related to members of the signal transducer and activator of transcription (STAT) family.

1994 ◽  
Vol 14 (5) ◽  
pp. 3186-3196 ◽  
Author(s):  
U M Wegenka ◽  
C Lütticken ◽  
J Buschmann ◽  
J Yuan ◽  
F Lottspeich ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Tyrosine Phosphorylation ◽  
Acute Phase ◽  
Interleukin 6 ◽  
Acute Phase Response ◽  
Leukemia Inhibitory Factor ◽  
Response Factor ◽  
Gamma Activation ◽  
Ifn Gamma ◽  
Activation Factor

Interleukin-6 (IL-6), leukemia inhibitory factor, oncostatin M, IL-11, and ciliary neurotropic factor are a family of cytokines and neuronal differentiation factors which bind to composite plasma membrane receptors sharing the signal transducing subunit gp130. We have shown recently that IL-6 and leukemia inhibitory factor rapidly activate a latent cytoplasmic transcription factor, acute-phase response factor (APRF), by tyrosine phosphorylation, which then binds to IL-6 response elements of various IL-6 target genes. Here we demonstrate that APRF is activated by all cytokines acting through gp130 and is detected in a wide variety of cell types, indicating a central role of this transcription factor in gp130-mediated signaling. APRF activation is also observed in vitro upon addition of IL-6 to cell homogenates. Protein tyrosine kinase inhibitors block both the tyrosine phosphorylation and DNA binding of APRF. The factor was purified to homogeneity from rat liver and shown to consist of a single 87-kDa polypeptide, while two forms (89 and 87 kDa) are isolated from human hepatoma cells. As reported earlier, the binding sequence specificity of APRF is shared by gamma interferon (IFN-gamma) activation factor, which is formed by the Stat91 protein. Partial amino acid sequence obtained from purified rat APRF demonstrated that it is likely to be related to Stat91. In fact, an antiserum raised against the amino-terminal portion of Stat91 cross-reacted with APRF, suggesting the relatedness of APRF and Stat91. Altogether, these data indicate that APRF belongs to a growing family of Stat-related proteins and that IFN-gamma and IL-6 use similar signaling pathways to activate IFN-gamma activation factor and APRF, respectively.

The interleukin-6-activated acute-phase response factor is antigenically and functionally related to members of the signal transducer and activator of transcription (STAT) family

1994 ◽  
Vol 14 (5) ◽  
pp. 3186-3196
Author(s):  
U M Wegenka ◽  
C Lütticken ◽  
J Buschmann ◽  
J Yuan ◽  
F Lottspeich ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Tyrosine Phosphorylation ◽  
Acute Phase ◽  
Interleukin 6 ◽  
Acute Phase Response ◽  
Leukemia Inhibitory Factor ◽  
Response Factor ◽  
Gamma Activation ◽  
Ifn Gamma ◽  
Activation Factor

Interleukin-6 (IL-6), leukemia inhibitory factor, oncostatin M, IL-11, and ciliary neurotropic factor are a family of cytokines and neuronal differentiation factors which bind to composite plasma membrane receptors sharing the signal transducing subunit gp130. We have shown recently that IL-6 and leukemia inhibitory factor rapidly activate a latent cytoplasmic transcription factor, acute-phase response factor (APRF), by tyrosine phosphorylation, which then binds to IL-6 response elements of various IL-6 target genes. Here we demonstrate that APRF is activated by all cytokines acting through gp130 and is detected in a wide variety of cell types, indicating a central role of this transcription factor in gp130-mediated signaling. APRF activation is also observed in vitro upon addition of IL-6 to cell homogenates. Protein tyrosine kinase inhibitors block both the tyrosine phosphorylation and DNA binding of APRF. The factor was purified to homogeneity from rat liver and shown to consist of a single 87-kDa polypeptide, while two forms (89 and 87 kDa) are isolated from human hepatoma cells. As reported earlier, the binding sequence specificity of APRF is shared by gamma interferon (IFN-gamma) activation factor, which is formed by the Stat91 protein. Partial amino acid sequence obtained from purified rat APRF demonstrated that it is likely to be related to Stat91. In fact, an antiserum raised against the amino-terminal portion of Stat91 cross-reacted with APRF, suggesting the relatedness of APRF and Stat91. Altogether, these data indicate that APRF belongs to a growing family of Stat-related proteins and that IFN-gamma and IL-6 use similar signaling pathways to activate IFN-gamma activation factor and APRF, respectively.

Sign in / Sign up

Export Citation Format

Share Document