Properties of transcription factors regulating interleukin-2 gene transcription through the NFAT binding site in untreated or drug-treated naive and memory T-helper cells.
Combining in vitro DNA binding studies and functional transcription assays in the Xenopus oocyte, we have tested the presence and functional state of transcription factors controlling the interleukin-2 (IL-2) promoter through the NFAT binding site. In naive T-helper cells, the IL-2 gene is repressed by a silencer. After first mitogenic stimulation, this silencer becomes undetectable while an activator is newly synthesized. In resting memory cells, the activator has low DNA-binding affinity and is located in the cytoplasm. However, no silencer is formed. Upon renewed cellular activation, this pre-existing activator is again targeted to the nucleus and regains function in promoting transcription. Cyclosporin A and FK506 act on two distinct levels of the IL-2 control mechanism. They prevent nuclear transport and reactivation of the performed activator in memory cells and, in naive cells, they render the silencer resistant to displacement by the activator. DNA-binding of silencer and activator from T-helper, and NFAT-1 from Jurkat cells, requires the same three G residues, but cross-linking analyses show differences in their constituent subunits. Supershift experiments show that the activator contains fra-2 and junD, whereas the silencer reacts with none of the antibodies tested.
Mouzaki
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Department of Medicine, Geneva University Hospital, Switzerland.
Rungger
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D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016572:Cyclosporine / Q000494:pharmacology; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics*; D015759:Ionomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D009865:Oocytes / Q000378:metabolism; D011401:Promoter Regions, Genetic; D018139:Simplexvirus / Q000201:enzymology; D006377:T-Lymphocytes, Helper-Inducer / Q000378:metabolism*; D016559:Tacrolimus / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013937:Thymidine Kinase / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014981:Xenopus
D004268:DNA-Binding Proteins; D007376:Interleukin-2; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors; D015759:Ionomycin; D016572:Cyclosporine; D004247:DNA; D013937:Thymidine Kinase; D013755:Tetradecanoylphorbol Acetate; D016559:Tacrolimus