Negative transcriptional regulation of the interferon-gamma promoter by glucocorticoids and dominant negative mutants of c-Jun.
Interferon-gamma (IFN-gamma) is an immunoregulatory cytokine expressed in large granular lymphocytes and T cells. However, the molecular mechanisms underlying IFN-gamma gene transcription have not been fully defined. Here, we analyze the mechanisms responsible for the inhibition of IFN-gamma promoter activity by the glucocorticoid hormone dexamethasone. Cotransfection assays performed in Jurkat T cells demonstrated that the activity of the initial 108 base pairs of the IFN-gamma promoter was down-regulated in the presence of dexamethasone. Furthermore, utilizing electrophoretic mobility shift analysis, we identified activator protein 1 AP-1-cAMP response element binding protein-activating transcription factor (CREB-ATF) binding elements situated in positions of the IFN-gamma promoter previously identified as essential for promoter activity. Moreover, dominant negative mutants of the c-Jun proto-oncogene were able to mimic the same down-regulatory effect exerted by dexamethasone, and mutations that abolished the binding of the AP-1 CREB-ATF factors were able to block the glucocorticoid effect. These results suggest a model involving the inhibition of IFN-gamma AP-1 CREB-ATF DNA binding complexes as one of the mechanisms involved in the negative regulatory action of glucocorticoids on IFN-gamma gene expression and support the relevance of AP-1 CREB-ATF binding factors during the transcriptional activation of the IFN-gamma promoter in T cells.
Cippitelli
M
M
Biological Carcinogenesis and Development Program, Program Resources Inc./DynCorp, Frederick, Maryland, USA.
Sica
A
A
Viggiano
V
V
Ye
J
J
Ghosh
P
P
Birrer
M J
MJ
Young
H A
HA
D001483:Base Sequence; D001665:Binding Sites; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004252:DNA Mutational Analysis; D003907:Dexamethasone / Q000494:pharmacology*; D015536:Down-Regulation; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000235:genetics; D015759:Ionomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D000090063:Proto-Oncogene Mas; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic
D017362:Cyclic AMP Response Element-Binding Protein; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D015759:Ionomycin; D003907:Dexamethasone; D007371:Interferon-gamma; D013755:Tetradecanoylphorbol Acetate