THE HUMAN PROINTERLEUKIN-1-BETA GENE REQUIRES DNA-SEQUENCES BOTH PROXIMAL AND DISTAL TO THE TRANSCRIPTION START SITE FOR TISSUE-SPECIFIC INDUCTION

In these studies, we have identified DNA sequences and specific protein interactions necessary for transcriptional regulation of the human prointerleukin 1beta (proIL-1beta) gene. A cell-type-independent lipopolysaccharide (LPS)-responsive enhancer element located between -3757 and -2729 bp upstream from the transcription start site (cap site) consisted of at least six discrete subregions which were essential to the maximal induction by LPS in transfected monocytes. The enhancer also appeared to mediate phorbol myristate acetate induction in monocytes and IL-1 responsiveness in fibroblasts. Deletion and base substitution mutations along with DNA binding studies demonstrated that the enhancer contained a minimum of three functional protein binding sequences, two of which appeared to be important for gene induction. One of the essential proteins which bound to the enhancer was similar or identical to members of the C/EBP family of transcription factors required for both IL-1- and LPS-specific induction of the IL-6 gene (i.e., the NF-IL6 proteins). When ligated to the proIL-1beta cap site-proximal region (located between -131 to +12), both the proIL-1beta and the simian virus 40 enhancer elements functioned more efficiently in monocytes than in HeLa cells, which are not normally competent for IL-1beta expression. When ligated to the murine c-fos promoter, however, the proIL-1beta enhancer was inducible in phorbol myristate acetate-stimulated HeLa cells, suggesting the existence of a proIL-1beta promoter-proximal requirement for tissue specificity.