Associations between promoter usage and alternative splicing of the glucocorticoid receptor gene

The glucocorticoid receptor (GR) is widely expressed in various tissues throughout the human body. At least three different 3'-splice variants of the GR have been reported: GR-alpha, which is functionally active; GR-beta, which is a dominant negative inhibitor of GR-alpha function; and GR-P, which is thought to activate the function of GR-alpha. At least seven different variants for exon 1 exist, 1A-1F and 1H, each with its own promoter. In this study, we explored if tissue-specific splicing of the 3'-end variants of the GR is influenced by alternative promoter usage. cDNAs of different tissues and cell lines were used to investigate which part of transcripts carrying each of the three major variants for exons 1, 1A, 1B, or 1C, encodes for the splice variants GR-alpha, GR-beta, and GR-P. Our data demonstrate that the expression of GR-alpha is preferentially regulated by promoter 1C and that for the expression of GR-P promoter 1B is predominantly used. This indicates that regulation of GR splice variants could partly occur through selective use of the multiple promoters, and that this is another way to sensitize cells and tissues to the different activities of the GR isoforms.