title: Quantification and glucocorticoid regulation of glucocorticoid receptor transcripts in two human leukemic cell lines.
abstract: We have quantified the basal and glucocorticoid-regulated levels of different transcripts from the human glucocorticoid receptor (GR) gene in the T-cell acute lymphoblastic leukemia cell line, CEM-C7, and in the B lymphoblastoid cell line, IM-9. Highly specific quantitative, reverse transcription-polymerase chain reaction assays measured total GR transcripts, transcripts encoding the isoforms glucocorticoid receptor alpha (GRalpha) and glucocorticoid receptor beta (GRbeta), and transcripts containing different forms of exon 1: 1A1, 1A2, 1A3, 1B, and 1C. GRalpha and GRbeta transcripts are coordinately upregulated in CEM-C7 cells and coordinately downregulated in IM-9 cells by dexamethasone. The concentration of GRalpha mRNA is more than a 1000-fold higher than that for GRbeta mRNA. Transcripts with different exon 1 forms are all upregulated in CEM-C7 cells and all downregulated in IM-9 cells by dexamethasone, but transcripts containing exons 1A1, 1A2, or 1A3 are regulated to a higher degree than transcripts containing exon 1B or exon 1C. However, exon 1B- and exon 1C-containing transcripts are substantially more abundant than exon 1A-containing transcripts, with exon 1A3-containing transcripts more abundant than exon 1A1- or exon 1A2-containing transcripts. Analysis using models for glucocorticoid receptor autoregulation kinetics suggests that the minor 1A3-containing transcript component could be important for GR protein upregulation, and hence apoptosis, in CEM-C7 cells. These studies suggest that GRalpha transcripts containing exons 1A3, 1B, and 1C contribute most to the intracellular level of GR mRNA and may be the most relevant for steroid-mediated apoptosis in T-lymphoblasts.
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: Kim Brint
authors.initials: KB
authors.lastname: Pedersen
authors.forename: Wayne V
authors.initials: WV
authors.lastname: Vedeckis
mesh_terms: D015153:Blotting, Western; D018076:DNA, Complementary / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation; D005091:Exons; D005938:Glucocorticoids / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007938:Leukemia / Q000378:metabolism*; D008956:Models, Chemical; D008957:Models, Genetic; D020033:Protein Isoforms; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000166:cytology; D013997:Time Factors; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D018076:DNA, Complementary; D005938:Glucocorticoids; D020033:Protein Isoforms; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D012313:RNA; D003907:Dexamethasone