c-Jun and c-Fos cooperate with STAT3 in IL-6-induced transactivation of the IL-6 respone element (IRE)

Cytokine. 2001 Apr 21;14(2):78-87. doi: 10.1006/cyto.2001.0856.


Transcriptional activation of eukaryotic genes often requires the cooperative action of many proteins. The interleukin 6 (IL-6) response element (IRE) is activated by signal transducer and activator of transcription 3 (STAT3), and stimulation with IL-6 leads to STAT3 tyr705 phosphorylation, dimerization, translocation to the nucleus and transactivation of target gene promoters containing IREs. Here, we report that IL-6 and 12-O-tetradecanoylphorbol-13-acetate (TPA) synergistically transactivate the IRE in HepG2 cells, which is coupled to a strong upregulation of c-Jun and c-Fos expression by TPA via the mitogen-activated protein kinase (MAPK) pathway. Overexpression of c-Jun and c-Fos strongly enhanced STAT3-driven IRE transactivation as well as transactivation of the human intercellular adhesion molecule (ICAM)-1 promoter. In contrast, c-Jun mutants lacking the transactivation domain, the DNA-binding domain, or mutants in which the serine residues 63 and 73 were replaced by alanine, did not cooperate with STAT3. In immunoprecipitation experiments, a direct association of STAT3 with c-Jun and c-Fos was observed in response to IL-6. Furthermore, c-Jun/STAT3 and c-Fos/STAT3 complexes were detected on IRE probes in electrophoretic mobility shift assay (EMSA) experiments, but did not bind nor transactivate the TPA response element (TRE). These results demonstrate that activator protein-1 (AP-1) transcription factors can cooperate with STAT3 in IRE transactivation in the absence of direct AP-1 DNA binding.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • DNA / genetics
  • DNA / metabolism
  • DNA-Binding Proteins / metabolism*
  • Genes, Reporter
  • Humans
  • Interleukin-6 / genetics*
  • Interleukin-6 / pharmacology*
  • Macromolecular Substances
  • Precipitin Tests
  • Protein Binding
  • Proto-Oncogene Proteins c-fos / genetics
  • Proto-Oncogene Proteins c-fos / metabolism*
  • Proto-Oncogene Proteins c-jun / genetics
  • Proto-Oncogene Proteins c-jun / metabolism*
  • Response Elements / genetics*
  • STAT3 Transcription Factor
  • Tetradecanoylphorbol Acetate / pharmacology
  • Trans-Activators / metabolism*
  • Transcriptional Activation / drug effects*
  • Tumor Cells, Cultured
  • Up-Regulation / drug effects


  • DNA-Binding Proteins
  • Interleukin-6
  • Macromolecular Substances
  • Proto-Oncogene Proteins c-fos
  • Proto-Oncogene Proteins c-jun
  • STAT3 Transcription Factor
  • STAT3 protein, human
  • Trans-Activators
  • DNA
  • Tetradecanoylphorbol Acetate