Differential hormone-dependent transcriptional activation and -repression by naturally occurring human glucocorticoid receptor variants
The molecular mechanisms underlying primary glucocorticoid resistance or hypersensitivity are not well understood. Using transfected COS-1 cells as a model system, we studied gene regulation by naturally occurring mutants of the glucocorticoid receptor (GR) with single-point mutations in the regions encoding the ligand-binding domain or the N-terminal domain reflecting different phenotypic expression. We analyzed the capacity of these GR variants to regulate transcription from different promoters, either by binding directly to positive or negative glucocorticoid-response elements on the DNA or by interfering with protein-protein interactions. Decreased dexamethasone (DEX) binding to GR variants carrying mutations in the ligand-binding domain correlated well with decreased capacity to activate transcription from the mouse mammary tumor virus (MMTV) promoter. One variant, D641V, which suboptimally activated MMTV promoter-mediated transcription, repressed a PRL promoter element containing a negative glucocorticoid-response element with wild type activity. DEX-induced repression of transcription from elements of the intercellular adhesion molecule-1 promoter via nuclear factor-kappaB by the D641V variant was even more efficient compared with the wild type GR. We observed a general DEX-responsive AP-1-mediated transcriptional repression of the collagenase-1 promoter, even when receptor variants did not activate transcription from the MMTV promoter. Our findings indicate that different point mutations in the GR can affect separate pathways of gene regulation in a differential fashion, which can explain the various phenotypes observed.
|Keywords||*Transcription, Genetic, *Variation (Genetics), Animals, COS Cells/metabolism, Collagenases/genetics/metabolism, Dexamethasone/metabolism/pharmacology, Humans, Intercellular Adhesion Molecule-1/genetics/metabolism, Luciferases/genetics/metabolism, Mammary Tumor Virus, Mouse/genetics, Mutation, NF-kappa B/genetics/metabolism, Prolactin/genetics/metabolism, Promoter Regions (Genetics), Receptors, Glucocorticoid/*genetics/*metabolism, Recombinant Proteins/genetics/metabolism, Tetradecanoylphorbol Acetate/pharmacology, Transcription Factor AP-1/drug effects/genetics/metabolism, Transfection|
de Lange, P., Koper, J.W., Huizenga, N.A.T.M., Brinkmann, A.O., de Jong, F.H., Karl, M., … Lamberts, S.W.J.. (1997). Differential hormone-dependent transcriptional activation and -repression by naturally occurring human glucocorticoid receptor variants. Molecular Endocrinology. Retrieved from http://hdl.handle.net/1765/8701