Open AccessRepression of FasL expression by retinoic acid involves a novel mechanism of inhibition of transactivation function of the nuclear factors of activated T‐cells
Author(s) -
Lee MiOck,
Kang HyoJin,
Kim Young Mi,
Oum JiHyun,
Park Jungchan
Publication year - 2002
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2002.02748.x
Subject(s) - nfat , transactivation , fas ligand , microbiology and biotechnology , reporter gene , retinoic acid , biology , transcription factor , psychological repression , promoter , gene expression , chemistry , apoptosis , gene , biochemistry , programmed cell death
Retinoids are potent immune modulators that inhibit Fas ligand (FasL) expression and thereby repress the activation‐induced apoptosis of immature thymocytes and T‐cell hybridomas. In this study, we demonstrate that all‐ trans ‐retinoic acid (all‐ trans ‐RA) directly represses the transcriptional activity of the nuclear factors of activated T‐cells (NFAT), which is an important transactivator of the FasL promoter. The analysis of reporter constructs containing the FasL promoter and wild‐type or mutant NFAT binding‐sites indicated that all‐ trans ‐RA repression was mediated via an NFAT binding element located in the promoter. A reporter construct comprising the NFAT binding sequence linked to a heterologous SV‐40 promoter showed that NFAT transcriptional activity was significantly inhibited by all‐ trans ‐RA. Furthermore, all‐ trans ‐RA inhibited activation of the distal NFAT binding motif present in the interleukin (IL)‐2 promoter, suggesting that the inhibition of NFAT function by all‐ trans ‐RA was not specific to the FasL promoter. Gel shift assays corroborated the results of the gene reporter studies by showing that all‐ trans ‐RA decreased the NFAT binding to DNA. All‐ trans ‐RA blocked translocation of NFATp from the cytosol into the nucleus, which was induced by PMA/ionomycin treatment in HeLa cells transfected with a Flag‐tagged NFATp. Taken together, our results indicate that FasL inhibition by all‐ trans ‐RA involves a novel mechanism whereby the transcriptional function of NFAT is blocked.