Characterization of the flounder IL-6 promoter and its regulation by the p65 NF-κB subunit

Interleukin (IL)-6 plays important roles in the regulation of the immune response and inflammation in many cell types and its induction by bacterial endotoxins or cytokines is regulated at the transcriptional level. The present study demonstrates the isolation and characterization of the flounder IL-6 promoter sequence and its transcriptional regulation in olive flounder (hirame) natural embryo (HINAE) cells. The promoter region (−400 to +79 bp from the transcription initiation site) of the flounder IL-6 gene contains putative cis-regulatory elements for CCAAT-enhancer-binding proteins (C/EBP; −346 to −355 bp and −166 to −160 bp), cAMP response element binding (CREB; −81 to −85 bp), the activator protein 1 (AP-1; −56 to −62 bp), and NF-κB (−39 to −48 bp). Transfection of p65 stimulated the PoIL-6-luc-WT reporter, but not the PoIL-6-luc-κB mt reporter, and treatment with LPS augmented p65-stimulated reporter activity in HINAE cells. In contrast, transfection of C/EBPβ or c-Jun failed to induce synergistic effects in the LPS-driven PoIL-6-luc-WT reporter activity. These results give us new insight into the regulation of flounder IL-6 transcription by the p65 NF-κB subunit.