A NOVEL SP-1 SITE IN THE HUMAN INTERLEUKIN-1-BETA PROMOTER CONFERS PREFERENTIAL TRANSCRIPTIONAL ACTIVITY IN KERATINOCYTES

To investigate the mechanisms of transcriptional activation of interle ukin-1 beta (IL-1 beta) in non-monocytic cells, we constructed a serie s of reporter plasmids with the bacterial chloramphenicol acetyltransf erase gene linked to various parts of the human IL-1 beta promoter and performed transient transfection experiments. We identified a promote r segment that activates transcription most efficiently in keratinocyt es. Electrophoretic mobility shift assays (EMSA) with a 43-mer oligonu cleotide derived from the functionally identified cis-acting element r evealed specific complexes. By competition analysis with transcription factor consensus sequence oligonucleotides and by immunosupershift, t ranscription factor SP-1 or a closely related protein was shown to bin d to this regulatory element. The closest match to the known SP-1 cons ensus sequence within the respective region is a TCCCCTCCCCT motif. Mu tation of this motif almost completely, and specifically, abolished th e binding of two low-mobility complexes and led to a 95 % decrease of constitutive transcriptional activation of a reporter construct IL-1 b eta (-170/+108). Likewise, activation of this reporter construct by tu mor necrosis factor-a depended on the SP-1 site. These observations su ggest that a so-far-unrecognized SP-1 site in the human IL-1 beta prom oter may participate in the transcriptional regulation of this gene in keratinocytes.