title: Interaction between the interferon signaling pathway and the human glucocorticoid receptor gene 1A promoter.
abstract: The newly described 1A promoter of the human glucocorticoid receptor (hGR) gene contains an interferon (IFN) regulatory factor element (IRF-E), a binding motif for the family of proteins termed IFN regulatory factors (IRFs) that are regulated by IFNs. To examine the in vivo role of IFNs in hGR gene regulation, human T cell lines (CEM-C7 and Jurkat) were treated with IFN gamma. IFN gamma rapidly induces the expression of IRF-1 proteins in a dose- and time-dependent manner. Luciferase expression is induced by IFN treatment in Jurkat cells transfected with an hGR 1A promoter IRF-E/luciferase reporter gene, but induction is lost with deletion of the IRF-E. Electrophoretic mobility shift and supershift analyses indicate an increase in the binding of IRF-1 to oligonucleotides containing the hGR 1A promoter IRF-E after IFN gamma treatment, whereas IRF-2 binding to this oligonucleotide is unchanged. Human IRF-1 and IRF-2 proteins expressed in Chinese hamster ovary cells bind to the hGR 1A promoter IRF-E; however, only IRF-1 activates transcription. Although IFNs clearly activate a transfected reporter gene containing the hGR 1A promoter in T cells, they do not alter the sensitivity of CEM-C7 cells to glucocorticoid-induced apoptosis. Additional studies revealed that the glucocorticoid steroid hormone, dexamethasone (DEX), completely blocks IFN induction of IRF-1 mRNA levels. This could explain the lack of any greater apoptotic response to a combination of DEX plus IFN compared with the response to DEX alone. In addition, treatment with IFN gamma alone does not alter endogenous GR mRNA levels (including exon 1A-containing transcripts derived from the hGR 1A promoter) in T lymphoblast cells, even though IRF-1 levels are induced. The difference in IRF-1-driven transcription between the hGR 1A reporter construct and the endogenous hGR 1A promoter could potentially be due to epigenetic effects, such as methylation.
authors.affiliation: Department of Biochemistry and Molecular Biology and Stanley S. Scott Cancer Center, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, Louisiana 70112, USA.
authors.forename: B Scott
authors.initials: BS
authors.lastname: Nunez
authors.forename: Chuan-Dong
authors.initials: CD
authors.lastname: Geng
authors.forename: Kim Brint
authors.initials: KB
authors.lastname: Pedersen
authors.forename: Candice D
authors.initials: CD
authors.lastname: Millro-Macklin
authors.forename: Wayne V
authors.initials: WV
authors.lastname: Vedeckis
mesh_terms: D020816:Amino Acid Motifs; D017209:Apoptosis; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005091:Exons; D005434:Flow Cytometry; D017930:Genes, Reporter; D005938:Glucocorticoids / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007372:Interferons / Q000378:metabolism*; D019169:Jurkat Cells; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation
chemical_list: D005938:Glucocorticoids; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D013778:Tetrazolium Salts; D013844:Thiazoles; D007371:Interferon-gamma; D004247:DNA; D007372:Interferons; D007770:L-Lactate Dehydrogenase; D008156:Luciferases; C022616:thiazolyl blue