Novel Egr/NF-AT composite sites mediate activation of the CD95 (APO-1/Fas) ligand promoter in response to T cell stimulation.
Expression of the CD95 (APO-1/Fas) ligand (CD95L) in activated T cells is a major cause of activation-induced T cell apoptosis. The transcription factors NF-AT and Egr-3 (a member of the immediate-early transcription factors involved in cellular growth and differentiation) have been implicated in activation of the CD95L promoter upon T cell activation. On the basis of DNase I footprinting, electrophoretic mobility shift assay, antibody supershift analysis and transfection studies, we have identified two novel Egr-binding sites 5' upstream of the previously identified Egr site. Mutation analysis of each Egr site shows that all three sites are important for full CD95L promoter activity. Strikingly, all Egr sites, including the previously identified Egr site, are adjacent to or overlap with DNA sequences homologous to NF-AT binding sites and confer T cell activation-induced, cyclosporin A-sensitive transcriptional activity. Antibody supershift analysis revealed that NF-AT and Egr proteins are the components of inducible DNA-binding complexes formed on the two novel Egr sites. Cotransfection experiments showed that Egr-1, Egr-3 and NF-AT display a cooperative and synergistic activation of transcription mediated by these three Egr/NF-AT composite regulatory elements. These findings provide further insight into the mechanisms involved in the regulation of the CD95L expression in response to T cell activation.
Li-Weber
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M
Tumor Immunology Program, German Cancer Research Center (DKFZ), Heidelberg, Germany. m.li-weber@dkfz-heidelberg.de
Laur
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O
Krammer
P H
PH
D000954:Antigens, Surface / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000276:immunology* / Q000378:metabolism; D051766:Early Growth Response Protein 1; D051776:Early Growth Response Protein 3; D053222:Fas Ligand Protein; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000276:immunology / Q000378:metabolism; D019169:Jurkat Cells; D008024:Ligands; D008213:Lymphocyte Activation / Q000187:drug effects / Q000235:genetics* / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000235:genetics*; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000276:immunology*; D014157:Transcription Factors / Q000276:immunology* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000378:metabolism
D000954:Antigens, Surface; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D017874:Immediate-Early Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; D019014:fas Receptor; D051776:Early Growth Response Protein 3; D016572:Cyclosporine