LIPOPOLYSACCHARIDE-MEDIATED INDUCTION OF THE BOVINE INTERLEUKIN-6 GENE IN MONOCYTES REQUIRES BOTH NF-KAPPA-B AND C EBP BINDING-SITES/

The interleukin-6 (IL-6) gene expression in bovine monocytes is highly induced following bacterial lipopolysaccharide (LPS) stimulation, To identify the promoter element(s) involved in the inducible transcripti on of IL-6, a 5'-flanking region containing 230 bp of the bovine IL-6 gene was linked to a reporter gene coding for bacterial chloramphenico l acetyltransferase (CAT) and analyzed for its ability to confer LPS-r esponsiveness to the reporter CAT gene in monocytic cells, Using mutan t reporter genes, we demonstrate that although mutation in the NF-kapp a B element produces the major loss of induction, both NF-kappa B and C/EBP elements are necessary for maximal transcriptional activation of the bovine IL-6 gene, Gel electrophoretic mobility-shift assays have detected induced DNA-binding activities in the LPS-stimulated monocyte s, Further characterization has revealed the activation and interactio n of C/EBP-alpha, C/EBP-beta (NF-IL6), NFKB1 (p50), and RelA (p65) to their specific binding elements present in the bovine IL-6 gene, These results suggest a model in which induction of C/EBP-alpha in differen tiating monocytes contributes and synergizes with induced C/EBP-beta a nd NF-kappa B, which are activated following LPS stimulation, to media te a high rate of IL-6 transcription under inflammatory conditions.