Quantification and glucocorticoid regulation of glucocorticoid receptor transcripts in two human leukemic cell lines.
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.
Pedersen
Kim Brint
KB
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.
Vedeckis
Wayne V
WV
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
D018076:DNA, Complementary; D005938:Glucocorticoids; D020033:Protein Isoforms; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D012313:RNA; D003907:Dexamethasone