Quantification and glucocorticoid regulation of glucocorticoid receptor transcripts in two human leukemic cell lines

Biochemistry. 2003 Sep 23;42(37):10978-90. doi: 10.1021/bi034651u.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Blotting, Western
  • DNA, Complementary / metabolism
  • Dexamethasone / pharmacology
  • Down-Regulation
  • Exons
  • Glucocorticoids / metabolism*
  • Humans
  • Kinetics
  • Leukemia / metabolism*
  • Models, Chemical
  • Models, Genetic
  • Protein Isoforms
  • RNA / metabolism
  • RNA, Messenger / metabolism*
  • Receptors, Glucocorticoid / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • T-Lymphocytes / cytology
  • Time Factors
  • Tumor Cells, Cultured
  • Up-Regulation

Substances

  • DNA, Complementary
  • Glucocorticoids
  • Protein Isoforms
  • RNA, Messenger
  • Receptors, Glucocorticoid
  • RNA
  • Dexamethasone