Glucocorticoid receptor-mediated suppression of the interleukin 2 gene expression through impairment of the cooperativity between nuclear factor of activated T cells and AP-1 enhancer elements

• Published in: The Journal of experimental medicine Vol. 175; no. 3; pp. 637 - 646
• Main Authors: VACCA, A, FELLI, M. P, FARINA, A. R, MARTINOTTI, S, MARODER, M, SCREPANTI, I, MECO, D, PETRONGALI, E, FRATI, L, GILINO, A
• Format: Journal Article
• Language: English
• Published: New York, NY Rockefeller University Press 01-03-1992; The Rockefeller University Press
• Subjects: Analysis of the immune response. Humoral and cellular immunity; Base Sequence; Biological and medical sciences; Dexamethasone - pharmacology; Down-Regulation - drug effects; Drug Synergism; Enhancer Elements, Genetic - physiology; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Gene Expression - drug effects; Immune Tolerance - drug effects; Immunobiology; Interleukin-1 - immunology; Interleukin-2 - genetics; Lymphocyte Activation; Lymphocyte Cooperation; Lymphokines, interleukins ( function, expression); Molecular Sequence Data; Receptors, Glucocorticoid - physiology; Regulatory factors and their cellular receptors; T-Lymphocytes - immunology; Transcription, Genetic; Transcription; Suppression; Molecular interaction; Activation; Gene expression; Glucocorticoid; In vitro; Plasmid; Regulation(control); Interleukin 2; T-Lymphocyte; Nuclear protein; Biological receptor
• ISSN: 0022-1007; 1540-9538
• DOI: 10.1084/jem.175.3.637

The immunosuppressant hormone dexamethasone (Dex) interferes with T cell-specific signals activating the enhancer sequences directing interleukin 2 (IL-2) transcription. We report that the Dex-dependent downregulation of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and calcium ionophore-induced activity of the IL-2 enhancer are mediated by glucocorticoid receptor (GR) via a process that requires intact NH2- and COOH-terminal and DNA-binding domains. Functional analysis of chloramphenicol acetyltransferase (CAT) vectors containing internal deletions of the -317 to +47 bp IL-2 enhancer showed that the GR-responsive elements mapped to regions containing nuclear factor of activated T cells protein (NFAT) (-279 to -263 bp) and AP-1 (-160 to -150 bp) motifs. The AP-1 motif binds TPA and calcium ionophore-induced nuclear factor(s) containing fos protein. TPA and calcium ionophore-induced transcriptional activation of homo-oligomers of the NFAT element were not inhibited by Dex, while AP-1 motif concatemers were not stimulated by TPA and calcium ionophore. When combined, NFAT and AP-1 motifs significantly synergized in directing CAT transcription. Such a synergism was impaired by specific mutations affecting the trans-acting factor binding to either NFAT or AP-1 motifs. In spite of the lack of hormone regulation of isolated cis elements, TPA/calcium ionophore-mediated activation of CAT vectors containing a combination of the NFAT and the AP-1 motifs became suppressible by Dex. Our results show that the IL-2-AP-1 motif confers GR sensitivity to a flanking region containing a NFAT element and suggest that synergistic cooperativity between the NFAT and AP-1 sites allows GR to mediate the Dex inhibition of IL-2 gene transcription. Therefore, a Dex-modulated second level of IL-2 enhancer regulation, based on a combinatorial modular interplay, appears to be present.