Despite numerous reports on IL-1 and the obvious importance of IL-1 in the cytokine network, very little is known regarding the molecular details of IL-1 regulation. While information is now emerging for IL-1 beta, mechanisms in IL-1 alpha gene regulation remain largely unknown. Examination of the 5'-flanking region of the human interleukin-1 alpha promoter (IL-1 alpha) and its first intron revealed several potential binding sites for known transcription factors. We thus studied this region by using an electrophoretic mobility shift assay (EMSA). EMSA studies showed that the region -12 to -6 of the human IL-1 alpha promoter contains an LPS-inducible AP-1-binding site composed of Jun and Fos proteins. On the other hand, no NF-kappa B binding within the IL-1 alpha promoter and its first intron was shown.