Molecular mechanisms regulating induction of interleukin-6 gene transcription by interferon-gamma.
The multifunctional cytokine interleukin-6 (IL-6) plays a central role in host defence mechanisms and hematopoiesis. Furthermore, dysregulation of IL-6 gene expression is associated with the pathogenesis of various immunologically related diseases such as myeloma, systemic lupus erythematosus, rheumatoid arthritis, psoriasis and Kaposi's sarcoma. The regulation of IL-6 gene expression occurs mainly at transcriptional level, although mechanisms of post-transcriptional regulation have also been described. In the present study we demonstrate that in HeLa cells, induction of IL-6 by interferon-gamma (IFN-gamma) is transcriptionally controlled, as shown by run on assays and analysis of the IL-6 mRNA stability. Gel-retardation experiments using antibodies specific for factors of the IRF family identified four protein-DNA complexes, which bind to the interferon regulatory factor (IRF) binding site at position -267 to -254, in nuclear extracts from IFN-gamma treated cells. Furthermore, transient transfection analyses of the 5'-flanking region of IL-6 gene linked to the chloramphenicol acetyltransferase (CAT) reporter gene demonstrated that the -267 to -254 IRF site is necessary for IL-6 induction by IFN-gamma. However, transfection experiments in which IRF-1 and I kappa B alpha were overexpressed show that full-scale transcriptional activation of the IL-6 promoter directing CAT expression requires the co-operation between IRF-1 and NF-kappa B at a low constitutive level.
Faggioli
L
L
Istituto di Chimica Biologica, Facoltà di Medicina e Chirurgia, Università di Verona, Italy.
Merola
M
M
Hiscott
J
J
Furia
A
A
Monese
R
R
Tovey
M
M
Palmieri
M
M
D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000276:immunology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006367:HeLa Cells; D006801:Humans; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis / Q000235:genetics*; D016328:NF-kappa B / Q000235:genetics; D010750:Phosphoproteins / Q000378:metabolism; D015534:Trans-Activators / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology*
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D015850:Interleukin-6; D016328:NF-kappa B; D010750:Phosphoproteins; D015534:Trans-Activators; D007371:Interferon-gamma