CCAAT/enhancer-binding proteins beta and delta mediate the repression of gene transcription of cartilage-derived retinoic acid-sensitive protein induced by interleukin-1 beta.
Cartilage-derived retinoic acid-sensitive protein (CD-RAP) is a secreted protein expressed by chondrocytes; the expression is repressed by interleukin 1 beta (IL-1 beta). To investigate the transcriptional mechanism, by which CD-RAP expression is suppressed by IL-1 beta, deletion constructs of the mouse CD-RAP promoter were transfected into rat chondrocytes treated with or without IL-1 beta. The results revealed an IL-1 beta-responsive element located between -2138 and -2068 bp. As this element contains a CAAT/enhancer-binding protein (C/ EBP) motif, the function of C/ EBP beta and C/ EBP delta was examined. IL-1 beta stimulated the expression of C/ EBP beta and -delta, and the direct binding of C/ EBP beta to the C/ EBP motif was confirmed. The -2251-bp CD-RAP promoter activity was down-regulated by co-transfection with C/ EBP expression vectors. Mutation of the C/ EBP motif abolished the inhibitory response to IL-1 beta. Additionally, C/ EBP expression vectors were found to down-regulate the construct containing the promoter and enhancer of the type II collagen gene. Finally, the enhancer factor, Sox9, was shown to bind adjacent to the C/ EBP site competing with C/ EBP binding. Taken together, these results suggest that C/ EBP beta and -delta may play an important role in the IL-1 beta-induced repression of cartilage-specific proteins and that expression of matrix proteins will be influenced by the availability of positive and negative trans-acting factors.[1]References
- CCAAT/enhancer-binding proteins beta and delta mediate the repression of gene transcription of cartilage-derived retinoic acid-sensitive protein induced by interleukin-1 beta. Okazaki, K., Li, J., Yu, H., Fukui, N., Sandell, L.J. J. Biol. Chem. (2002) [Pubmed]
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