Binding of C/EBP and RBP (CBF1) to overlapping sites regulates interleukin-6 gene expression.
The ILRE (interleukin response element) contained within the promoter of the interleukin-6 (IL-6) gene is defined as the site recognized by the p65 NF-kappaB transcriptional activator and is crucial for activation of the IL-6 gene. The region of the promoter containing the ILRE is complex containing a CCAAT enhancer-binding protein (C/EBP) site immediately upstream of the ILRE, which is required for optimal activation of the IL-6 gene. Additionally, the ILRE overlaps a site that is recognized by the mammalian transcriptional repressor RBP (CBF-1), and RBP binding within the ILRE region represses activated IL-6 expression. In this study, the complexity of this region is further revealed by the identification of a second nested C/EBP site, which overlaps that of RBP and therefore also the ILRE. Optimal activation requires both the upstream and newly identified C/EBP sites in conjunction with the p65 NF-kappaB binding site. We previously reported that RBP represses IL-6 activation but does not target p65. We extend these analyses here to show that RBP binding does not occlude p65 from binding but instead directly overlaps the newly identified downstream C/EBP site, thereby impeding p65-C/EBP-mediated co-activation. This result suggests a role for RBP in the repression of other genes containing a C/EBP site that exhibits sequence overlap with the RBP site.
Vales
Lynne D
LD
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854-5635, USA. valesly@umdnj.edu
Friedl
Erika M
EM
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D015850:Interleukin-6 / Q000235:genetics*; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000276:immunology; D016385:TATA Box; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D015850:Interleukin-6; D016328:NF-kappa B; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; C497570:RBPJ protein, human; D011994:Recombinant Proteins