title: Synergistic action of interleukin-6 and glucocorticoids is mediated by the interleukin-6 response element of the rat alpha 2 macroglobulin gene.
abstract: One class of genes coding for the acute-phase proteins (acute-phase genes) is induced by interleukin 6 (IL-6) through the human transcription factor NF-IL-6 and its rat homolog IL-6-DBP/LAP. A second class, represented by the rat alpha 2 macroglobulin gene, utilizes a different IL-6 response element (IL-6-RE) and different DNA-binding proteins interacting with this element, the so-called IL-6-RE binding proteins (IL-6 RE-BPs). Human Hep3B and HepG2 hepatoma, U266 myeloma, and CESS lymphoblastoid cells contain IL-6 RE-BPs that form complexes, with the IL-6-RE, with gel mobilities indistinguishable from those of the corresponding complexes of rat liver cells. The ability to form these complexes was induced by IL-6 in human hepatoma cells with a maximum reached after 4 h and required ongoing protein synthesis. Multiple copies of an 18-bp element containing the IL-6-RE core were sufficient to confer both induction by IL-6 and a synergistic induction by IL-6 plus glucocorticoids to minimal promoters. The synergism was blocked by the receptor antagonist RU486 and thus was dependent on the glucocorticoid receptor (GR). However, the 18-bp element contained no consensus GR-binding site, and recombinant GR did not bind at this sequence. Therefore, the synergism was probably achieved by an indirect effect of a glucocorticoid-activated intermediate gene on the IL-6 RE-BPs. The rat IL-6 RE-BP had a molecular weight of 102 +/- 10 kDa and was thus distinct from NF-IL-6 and IL-6-DBP/LAP. Therefore, IL-6 must activate two different classes of liver acute-phase genes through at least two different nuclear DNA-binding proteins: NF-IL-6/IL-6-DBP/LAP and the IL-6 RE-BP.
authors.affiliation: Department of Immunology, Research Institute of Scripps Clinic, La Jolla, California 92037.
authors.forename: G M
authors.initials: GM
authors.lastname: Hocke
authors.forename: D
authors.initials: D
authors.lastname: Barry
authors.forename: G H
authors.initials: GH
authors.lastname: Fey
mesh_terms: D000818:Animals; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D004357:Drug Synergism; D005809:Genes, Regulator / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000502:physiology*; D008113:Liver Neoplasms; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009101:Multiple Myeloma; D015345:Oligonucleotide Probes; D010957:Plasmids; D051381:Rats; D015183:Restriction Mapping; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D000511:alpha-Macroglobulins / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D015850:Interleukin-6; D015345:Oligonucleotide Probes; D014157:Transcription Factors; D000511:alpha-Macroglobulins