Distinct role of IL-3 promoter and enhancer region in murine mast cells

Crosslinking of Fcε receptor on mast cells induces IL-3 gene expression with the concentration dependent of intracellular calcium, but its regulatory mechanism remains unclear. Here, we found that phorbol 12-myristate 13-acetate (PMA) alone did not induce IL-3 gene expression, but potentiated A23187-induced IL-3 gene expression. Interestingly, the A23187-induced IL-3 promoter activity was suppressed by PMA, but it was enhanced when IL-3 promoter contained enhancer region, a DH site. While IL-3 mRNA expression was increased by A23187 and PMA in a dose-dependent manner, the promoter activity appeared all or none in all doses of A23187 and PMA. IL-3 promoter region between -293 and -150 bp was responsible for A23187-induced gene expression and PMA- or cyclosporin A (CsA)-mediated suppression. Taken together, IL-3 gene expression was primarily regulated at the transcriptional level, which was differentially controlled by a restricted promoter and enhancer region.