CHARACTERIZATION OF A 2ND TRANSCRIPTION INITIATION ELEMENT (STIE) IN THE HUMAN INTERLEUKIN-1-BETA (IL-1-BETA) GENE

Interleukin-1-beta (IL-1 beta) is a significant mediator in the inflam mation process. Although the human IL-1 beta genomic sequence has been known for several years, our understanding of its molecular regulatio n of transcription remains incomplete. We are reporting a new transcri ption initiation element that is located within intron 1 and exon 2 of the human IL-1 beta gene. Different lengths of the human IL-1 beta ge ne fragment (-685 to +550) were cloned upstream from a chloramphenical acetyltransferase (CAT) gene to make the IL-1 beta promoter/CAT repor ter constructs. Transient CAT expression with these constructs in the human monocytic leukemia cell line THP1 illustrates an important posit ive regulatory element exists within the region from +387 to +550. Usi ng electromobility shift assays and by DNase I footprinting analysis, we identified three nuclear factor binding sites (+448 to +502, +513 t o +531, and +539 to +548). Functional studies show that CAT production is undetectable when the 19 bp region (+513 to +531) is removed, and CAT production is diminished when the 10-bp region (+539 to +548) is d eleted. The region containing these sites is likely to initiate a new transcript starting at +559 of exon 2. This second transcript of the I L-1 beta gene shares the same reading frame with the previously recogn ized cDNA transcript.