The role of NF-kappa B and NF-IL6 transactivating factors in the synergistic activation of human serum amyloid A gene expression by interleukin-1 and interleukin-6.
To understand the mechanisms by which large increases in serum amyloid A (SAA) occur during the acute phase response, human hepatoma cells were transfected with SAA2 gene reporter plasmids and stimulated with combinations of cytokines. Although interleukin-1 (IL-1) and interleukin-6 (IL-6) stimulated transcription from this promoter individually, addition of both mediators produced a response between two and nine times greater than the expected additive response. This synergistic activation was dependent on the integrity of at least two cis-acting sequences in the SAA2 enhancer. The SAA2 NF-kappa B site was required functionally for the response to both IL-1 and IL-6 alone as well as for synergistic activation; however, IL-6 did not directly induce binding of nuclear proteins to the NF-kappa B sequence. A NF-IL6 site was required for full induction by IL-1 and IL-6, and also mediated strong transactivation by recombinant NF-IL6. Furthermore, transfected NF-IL6 synergized strongly with co-transfected NF-kappa B, particularly with RelA (p65). However synergy between IL-1 and IL-6 was only partly reduced by mutation of the NF-IL6 site, indicating further levels of interaction in addition to the NF-kappa B/NF-IL6 cooperativity.
Betts
J C
JC
Section of Molecular Rheumatology, Medical Research Council Clinical Research Center, Harrow, United Kingdom.
Cheshire
J K
JK
Akira
S
S
Kishimoto
T
T
Woo
P
P
D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004357:Drug Synergism; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D007700:Kinetics; D008745:Methylation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000096:biosynthesis / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D014176:Protein Biosynthesis; D000685:Serum Amyloid A Protein / Q000096:biosynthesis*; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D007375:Interleukin-1; D015850:Interleukin-6; D016328:NF-kappa B; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D000685:Serum Amyloid A Protein; D014157:Transcription Factors