The human beta fibrinogen promoter contains a hepatocyte nuclear factor 1-dependent interleukin-6-responsive element.
Acute-phase reactants are liver proteins whose synthesis is positively or negatively regulated during inflammation. The main mediators of this phenomenon are glucocorticoids and interleukin-6 (IL-6), a pleiotropic cytokine that also controls hematopoiesis. Functional analysis of several acute-phase reactant promoter regions has identified two major DNA motifs used by IL-6-regulated genes. The first one corresponds to a CTGG(G/A)AA sequence, and the other is a binding site for members of the C/EBP family of nuclear proteins. We have previously shown that the human beta fibrinogen (beta Fg) promoter contains an IL-6-responsive region, located between bp -150 and -67 (P. Huber, M. Laurent, and J. Dalmon, J. Biol. Chem. 265:5695-5701, 1990). In this study, using DNase I footprinting, mobility shift assays, and mutagenesis, we demonstrate that at least three subdomains of this region are necessary to observe a full response to IL-6. The most distal contains a CTGGGAA motif, and its mutation inhibits IL-6 stimulation. Another, which is able to interact with several distinct nuclear proteins, among them members of the C/EBP family, is dispensable for IL-6 induction but plays an important role in the constitutive expression of beta Fg. Finally, a proximal hepatocyte nuclear factor 1 binding site, already described as the major determinant of beta Fg tissue-specific expression, is also required for IL-6 stimulation. These results indicate a complex interplay between nuclear proteins within the beta Fg IL-6-responsive region and suggest a tight functional coupling between the tissue-specific and inducible elements.
Dalmon
J
J
Département de Biologie Moléculaire et Structurale, INSERM Unité 217, Grenoble, France.
Laurent
M
M
Courtois
G
G
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D005340:Fibrinogen / Q000235:genetics*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D015850:Interleukin-6 / Q000502:physiology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D015850:Interleukin-6; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D005340:Fibrinogen; D004247:DNA