NEGATIVE TRANSCRIPTIONAL REGULATION OF HUMAN INTERLEUKIN-2 (IL-2) GENE BY GLUCOCORTICOIDS THROUGH INTERFERENCE WITH NUCLEAR TRANSCRIPTION FACTORS AP-1 AND NF-AT

IL-2 gene transcription is affected by several nuclear proteins. We as ked whether dexamethasone (Dex) and cyclosporin A (CsA) inhibit IL-2 g ene transcription by interfering with the activity of nuclear proteins that bind to the IL-2 promoter. Nuclear extracts from primary human T lymphocytes were analyzed by electrophoretic DNA mobility shift assay s. Both Dex and CsA inhibited the binding of transcription factors AP- 1 and NF-AT, but not of NF-kB and OCT-1/OAF, to their corresponding si tes on the IL-2 gene promoter. To correlate changes in nuclear factor binding in vitro with transcriptional activity in vivo and define the structural requirements for IL-2 promoter repression, we used transien t DNA transfections. Jurkat cells were transfected with plasmids conta ining either the intact IL-2 promoter or its AP-1, NF-AT, and NF-kB mo tifs. Dex inhibited the IL-2 promoter and the AP-1, but not the NF-AT and NF-kB plasmids. In contrast, CsA inhibited the IL-2 promoter and t he NF-AT, but not the AP-1 and NF-kB plasmids. These results suggest t hat in human T lymphocytes both Dex and CsA inhibited IL-2 gene transc ription through interference with transcription factors AP-1 and NF-AT . We propose that, while maximum inhibition may involve interaction wi th both transcription factors, AP-1 is the primary target of Dex.