PMA/ionomycin induces Igκ 3′ enhancer activity which is in part mediated by a unique NFAT transcription complex

• Published in: European journal of immunology 1998-05, Vol.28 (5), p.1467-1480
• Main Authors: Meyer, Kerstin B., Ireland, John
• Format: Article
• Language: English
• Subjects: Animals; B-Lymphocytes - immunology; B-Lymphocytes - metabolism; Cell Line; Cyclosporine - pharmacology; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - metabolism; DNA-Binding Proteins - physiology; Drug Synergism; Enhancer; Enhancer Elements, Genetic - drug effects; Enhancer Elements, Genetic - immunology; Gene expression; Gene Expression Regulation - drug effects; Gene Expression Regulation - immunology; Humans; Immunoglobulin; Immunoglobulin kappa-Chains - biosynthesis; Immunoglobulin kappa-Chains - genetics; Immunoglobulin kappa-Chains - physiology; Ionomycin - pharmacology; Mice; Mice, Inbred C57BL; Mice, Transgenic; NFAT; NFATC Transcription Factors; Nuclear Proteins; Protein Binding - genetics; Protein Binding - immunology; Proto-Oncogene Proteins c-fos - metabolism; Proto-Oncogene Proteins c-jun - metabolism; Receptors, Antigen, B-Cell - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Transcription Factors - biosynthesis; Transcription Factors - metabolism; Transcription Factors - physiology; Transcriptional Activation - drug effects; Transcriptional Activation - immunology; Up-Regulation - drug effects; Up-Regulation - genetics; Up-Regulation - immunology; κ light chain
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/(SICI)1521-4141(199805)28:05<1467::AID-IMMU1467>3.0.CO;2-9

The Igκ 3′ enhancer is required for high levels of Igκ gene expression. We now show that κ3′ 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 κ3′ 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 cross‐linking of surface Ig. We have, thus, identified a unique NFAT complex in B cells that contributes to Igκ gene expression.