The ovine CCAAT-enhancer binding protein delta gene: Cloning, characterization, and species-specific autoregulation

Transcription factors belonging to the CCAAT-enhancer binding protein (C/EB P) family have been implicated in the regulation of gene expression during growth, differentiation, apoptosis, and inflammation. Autoregulation is rel atively common in the modulation of C/EBP gene expression and, for the huma n and murine C/EBP alpha, it is known that species-specific autoregulatory mechanisms operate. It is therefore essential to investigate the autoregula tion of additional C/EBP genes from a wider range of different species to g auge the degree of commonality, or otherwise, which exists. As an important step towards this goal, we report here the cloning and the characterisatio n of the ovine C/EBP delta gene (ovC/EBP delta) and analysis of its promote r region. Transient transfection assays reveal that ovC/EBP delta acts as a transcriptional activator. Although several motifs that are characteristic of C/EBP delta genes are conserved in the ovine sequence, including the ba sic region, leucine zipper, and activation domains, two regions have been i dentified that are specifically absent in the ovine and bovine homologues. The ovC/EBP delta promoter is active in both the hepatoma Hep3B and the mam mary epithelial HC11 cell lines, induced by the cytokine interleukin-6 and autoregulated by mechanisms that are potentially different from those descr ibed for the rat promoter. These results suggest that, in common with C/EBP alpha, the C/EBP delta genes may also be subject to autoregulation by dist inct species-specific mechanisms. (C) 2000 Academic Press.