EGR-1 AND SP1 INTERACT FUNCTIONALLY WITH THE 5-LIPOXYGENASE PROMOTER AND ITS NATURALLY-OCCURRING MUTANTS

5-Lipoxygenase (5-LO), an enzyme essential for the formation of leukot rienes, is functionally modulated by a number of mechanisms, including transcriptional controls. The 5-LO promoter has a unique G+C-rich seq uence, located between 176 and 147 base pairs upstream of the ATG tran slation start site, which contains five tandem Sp1 (a zinc-finger tran scription factor) consensus binding sites overlapping five tandem earl y growth response protein 1 (Egr-1), a zinc-finger transcription facto r, consensus binding sites. A family of naturally occurring mutations has been identified that consists of additions or deletions of these b inding sites. The role of these overlapping Sp1/Egr-1 sites in the reg ulation of 5-LO transcription and the effects of these mutations on tr anscriptional regulatory mechanisms are unknown. We now show that Spl and Egr-1 bind specifically to the G+C-rich promoter sequence using in vitro deoxyribonuclease I footprinting. Both Sp1 and Egr-1 activate 5 -LO promoter-reporter constructs in a minimally active drosophila SL2 cotransfection system, and the G+C-rich sequence is involved in this p rocess. Moreover, studies comparing mutant promoter function indicate that both Spl and Egr-1 trans-activation are proportional to the numbe r of Sp1/Egr-1 consensus binding sites within the G+C-rich sequence. I t is possible that basal and inducible 5-LO gene transcriptions are me diated by an interplay of Sp1, Egr-1, and other transcription factors within the G+C-rich promoter region, and the naturally occurring mutat ions alter transcription by modifying their trans-activation potential .