Utilization of an NF-ATp binding promoter element for EGR3 expression in T cells but not fibroblasts provides a molecular model for the lymphoid cell-specific effect of cyclosporin A.
Cyclosporin A (CsA) mainly exerts its immunosuppressive action by selectively inhibiting Ca2+/calcineurin-dependent gene transcription in lymphoid cells. A model explaining the tissue-specific effect of this drug on gene expression has not been established to date, since none of the known intracellular targets of CsA (e.g., cyclophilins, calcineurin, and NF-AT) is lymphoid cell specific. To investigate this issue, we performed a detailed comparative analysis of the promoter regulating the two-signal-dependent (Ca2+ ionophore plus phorbol myristate acetate [PMA]), CsA-sensitive expression of EGR3 in T cells and the one-signal-dependent (PMA), CsA-insensitive expression of EGR3 in fibroblasts. As a result, we identified a 27-bp promoter element functionally interacting with transcription factors NF-ATp and NF-ATc that is crucial for the CsA-sensitive expression of the EGR3 gene in T cells. In contrast, the same element was without function in fibroblasts, and other, CsA-insensitive promoter regions were found to be responsible for EGR3 gene expression in these cells. The inactivity of the 27-bp element in fibroblasts was apparently due to insufficient expression levels of NF-ATp, since overexpression of NF-ATp, but not NF-ATc, restored the two-signal phenotype and CsA sensitivity of EGR3 promoter induction in these cells. The differential usage of an NF-AT binding site explains the selective effect of CsA on EGR3 gene expression in T cells versus fibroblasts and may represent one of the basic mechanisms underlying the tissue specificity of CsA.
Mages
H W
HW
Molecular Immunology, Robert Koch-Institute, D-13353 Berlin, Germany. magesh@rki.de
Baag
R
R
Steiner
B
B
Kroczek
R A
RA
D001483:Base Sequence; D016572:Cyclosporine / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D051776:Early Growth Response Protein 3; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005347:Fibroblasts; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D005809:Genes, Regulator / Q000235:genetics; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D019169:Jurkat Cells; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins / Q000032:analysis; D009838:Oligodeoxyribonucleotides / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D017384:Sequence Deletion / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics
D004268:DNA-Binding Proteins; D007166:Immunosuppressive Agents; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D014157:Transcription Factors; D051776:Early Growth Response Protein 3; D016572:Cyclosporine