IDENTIFICATION OF A NOVEL INTERLEUKIN-6 RESPONSE ELEMENT CONTAINING AN ETS-BINDING SITE AND A CRE-LIKE SITE IN THE JUNB PROMOTER

Interleukin-6 (IL-6) activation of the immediate-early gene junB has b een shown to require both a tyrosine kinase and an unknown 1-(5-isoqui nolinesulfonyl)-2-methylpiperazine (H7)-sensitive pathway. Here we rep ort the identification and characterization of an IL-6 immediate-early response element in the junB promoter (designated JRE-IL6) in HepG2 c ells. The JRE-IL6 element, located at -149 to -124, contains two DNA m otifs, an Ets-binding site (EBS) (CAGGAAGC) and a CRE-like site (TGACG CGA). Functional studies using variously mutated JRE-IL6 elements show ed that both motifs were necessary and sufficient for IL-6 response of the promoter. The EBS of the JRE-IL6 element (JEBS) appears to bind a protein in the Ets family or a related protein which could also form a major complex with the EBSs of the murine sarcoma virus long termina l repeat or human T-cell leukemia virus type 1 long terminal repeat. T he CRE-like site appears to weakly bind multiple CREB-ATF family prote ins. Despite the similarity in the structure between the JRE-IL6 eleme nt and the polyomavirus enhancer PyPEA3, composed of an EBS and an AP1 -binding site and known to be activated by a variety of oncogene signa ls, JRE-IL6 could not be activated by activated Ha-Ras, Raf-1, or 12-0 -tetradecanoylphorbol-13-acetate. We show that IL-6 activates JRE-IL6 through an H7-sensitive pathway that does not involve protein kinase C , cyclic AMP-dependent kinase, Ca2+ - or calmodulin-dependent kinases, Ras, Raf-1, or NF-IL6 (C/EBPbeta). The combination of JEBS and the CR E-like site appears to form the basis for the selective and efficient response of JRE-IL6 to IL-6 signals, but not to signals generated by a ctivated Ha-Ras, Raf-1, or protein kinase C.