C/EBP regulates the promoter of the eosinophil-derived neurotoxin/RNS2 gene in human eosinophilic cells

The eosinophil-derived neurotoxin (EDN), a member of the mammalian ribonucl ease family, is found in the large specific granules of human eosinophilic leukocytes. We have investigated the role of the C/EBP transcription factor family in the regulation of EDN promoter activity. Here we show that the C /EBP family is involved in intrinsic regulation of EDN promoter activity. W e have identified a C/EBP binding site located at -124 in the proximal prom oter of the EDN gene. Mutation of this C/EBP site results in a decrease of promoter activity in HL-60-eos cells as well as in eosinophils differentiat ed in vitro from CD34(+) cells. Different C/EBP proteins are able to bind t o the C/EBP site as shown by gel shift assay. Our results indicate the impo rtance of the C/EBP family in the regulation of the EDN gene in eosinophils .