AN NFIL-6 SEQUENCE NEAR THE TRANSCRIPTIONAL INITIATION SITE IS NECESSARY FOR THE LIPOPOLYSACCHARIDE INDUCTION OF MURINE INTERLEUKIN-1-BETA

We have analyzed the interleukin-l beta (IL-1 beta) promoter region ne ar the cap site. Specific DNA sequences required for lipopolysaccharid e (LPS) induction within this region were identified using transfectio n of reporter plasmids that contained portions of the proximal IL-1 be ta 5 '-flanking sequence. An LPS-responsive activation area was locali zed between nucleotides -50 to -100, and down-regulating sequences wer e present between nucleotides -100 and -2,111. A NFIL-6 site between - 92 and -84 was identified in the functionally active region. Base subs titutions within this single NFIL-6 site in the context of a 4.1-kb IL -1 beta promoter segment resulted in dramatic reduction of LPS-induced gene transcription. Introduction of multimers of this NFIL-6 sequence immediately 5 ' to minimal homologous or heterologous promoters confe rred LPS inducibility in each case. Anti-C/EBP beta (NFIL-6) and anti- C/EBP delta (NFIL-6 beta) antibodies identified both of these proteins in complexes formed between the NFILd site and mononuclear cell nucle ar extracts. These data show that the proximal NFIL-6 site is required for the activation of murine IL-1 beta gene expression by endotoxin.