Characterization of mechanisms of interleukin-6 gene repression by estrogen receptor.
Estrogens are the most effective agents available for preventing osteoporosis, and their principal role in bone metabolism is the inhibition of interleukin-6 (IL-6) production in osteoblasts and bone marrow stromal cells. We examined the mechanism of inhibitory effect of estrogens on the 190 bp proximal promoter of the IL-6 gene. Promoter activity induced by transfection of both NF-kappaB p65 subunit and NF-IL6 was decreased by 45% by estradiol (E2)-estrogen receptor (ER) complexes. The inhibitory effect of E2 was also observed on a mutant IL-6 promoter in which the NF-IL6 binding site was disrupted. E2 repressed the wild-type promoter activity induced by NF-kappaB p65 subunit alone, but had no effect on that induced by NF-IL6 alone. These findings suggested that estrogens inhibit IL-6 production by interfering with the function of NF-kappaB rather than that of NF-IL6. The ER mutant, HE19, which does not contain the A/B domain, repressed the induction by NF-kappaB to the same extent as wild-type ER HE0, whereas the effect of C-terminal deletion mutant, HE21, was only marginal. The antiestrogen, 4-hydroxytamoxifen (OHT), had no effect on IL-6 promoter activity, suggesting that E2-induced conformational change of the hormone binding domain plays an important role in protein-protein interaction between ER and NF-kappaB. E2 had no effect on the nuclear translocation of NF-kappaB, and electrophoretic mobility shift assay showed that the presence of E2-ER complexes did not affect the ability of NF-kappaB to bind to specific DNA sequences.
Kurebayashi
S
S
Department of Medicine III, Osaka University Medical School, Suita, Japan.
Miyashita
Y
Y
Hirose
T
T
Kasayama
S
S
Akira
S
S
Kishimoto
T
T
D000818:Animals; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D019556:COS Cells / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D015850:Interleukin-6 / Q000235:genetics* / Q000378:metabolism; D008156:Luciferases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D016328:NF-kappa B / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D011960:Receptors, Estrogen / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D014162:Transfection
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D004965:Estrogen Antagonists; D015850:Interleukin-6; D016328:NF-kappa B; D009687:Nuclear Proteins; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol; D008156:Luciferases