TRANSCRIPTIONAL REGULATION OF THE HUMAN IL5 GENE BY IONIZING-RADIATION IN JURKAT T-CELLS - EVIDENCE FOR REPRESSION BY AN NF-AT-LIKE ELEMENT

Eosinophilia is often observed in patients with parasitic infections a nd atopic diseases like allergic asthma and atopic dermatitis. Additio nally, it is a typical feature of the inflammatory reaction after ther apeutic and accidental exposure to ionizing radiation. This uniquely s pecific phenomenon regulated by the cytokine interleukin 5 (IL-5) sugg ests specific control for IL5 gene expression. In this study, we gener ated promoter-CAT constructs containing different human IL-5 promoter regions spanning from positions -507 to +43. Transfection experiments in Jurkat T cells revealed that the promoter sequence from -57 to +43 was required for constitutive and inducible IL-5 promoter activity. Lo w baseline CAT activity could be enhanced by treatment with phenylmerc uric acetate (PMA) or the combination of PMA and calcium ionophore. Th e promoter region between positions -97 and +43 showed responsiveness to low-dose X rays. Electrophoretic mobility shift assays demonstrated that the region from -117 to -97 was responsive to irradiation. Trans cription factors specifically bound to this sequence showed a dose-dep endent response to single doses of X rays between 1 and 8 Gy. Competit ion analysis indicated that the protein-DNA complexes at this region w ere related to the nuclear factor of activated T cells (NF-AT). Furthe r confirmation was obtained by the addition of specific antibodies int o protein-DNA reactions. For the first time, we have demonstrated that specific DNA binding of NF-ATp at the promoter region from -117 to -9 7 is involved in transcriptional regulation of the human IL5 gene in r esponse to ionizing radiation. (C) 1997 by Radiation Research Society.