PMA/ionomycin induces Ig kappa 3' enhancer activity which is in part mediated by a unique NFAT transcription complex.
The Ig kappa 3' enhancer is required for high levels of Ig kappa gene expression. We now show that kappa 3' enhancer function increases five- to eightfold after stimulation of primary murine B cells with phorbol 12-myristate 13-acetate (PMA) and the calcium ionophore ionomycin. In the presence of cyclosporin A this induction is almost halved, suggesting that transcription factors of the NFAT family contribute to kappa 3' enhancer induction. Indeed, we identify a novel NFAT binding site which is required for full enhancer function. We find that this site is transcriptionally active in stimulated B cells, T cells and fibroblasts and that both PMA and ionomycin are required for maximal induction. Time course analysis of the components of the protein-DNA complex in primary lymphocytes reveals that both NFATp and NFATc are present in the complex after 15 min, while only NFATc is detectable after 4 h. This suggests that NFATc plays the dominant role in controlling long-term responses of this transcription factor family. Furthermore, JunB, JunD, FosB and cFos form part of the DNA-protein complex in Bal-17 B cells. Complex formation as well as transcriptional activity can also be induced by crosslinking of surface Ig. We have, thus, identified a unique NFAT complex in B cells that contributes to Ig kappa gene expression.
Meyer
K B
KB
The Wellcome/CRC Institute of Cancer and Developmental Biology, Department of Pathology, University of Cambridge, GB. kbm1000@mole.bio.cam.ac.uk
Ireland
J
J
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D004357:Drug Synergism; D004742:Enhancer Elements, Genetic / Q000187:drug effects / Q000276:immunology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D015759:Ionomycin / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects / Q000276:immunology; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics / Q000276:immunology
D004268:DNA-Binding Proteins; D007145:Immunoglobulin kappa-Chains; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011947:Receptors, Antigen, B-Cell; D014157:Transcription Factors; D015759:Ionomycin; D016572:Cyclosporine; D013755:Tetradecanoylphorbol Acetate