Glucocorticoid receptor (GR) β has intrinsic, GRα-independent transcriptional activity

The human glucocorticoid receptor (GR) gene produces C-terminal GRβ and GRα isoforms through alternative use of specific exons 9β and α, respectively. We explored the transcriptional activity of GRβ on endogenous genes by developing HeLa cells stably expressing EGFP-GRβ or EGFP. Microarray analyses revealed that GRβ had intrinsic gene-specific transcriptional activity, regulating mRNA expression of a large number of genes negatively or positively. Majority of GRβ-responsive genes was distinct from those modulated by GRα, while GRβ and GRα mutually modulated each other's transcriptional activity in a subpopulation of genes. We did not observe in HCT116 cells nuclear translocation of GRβ and activation of this receptor by RU 486, a synthetic steroid previously reported to bind GRβ and to induce nuclear translocation. Our results indicate that GRβ has intrinsic, GRα-independent, gene-specific transcriptional activity, in addition to its previously reported dominant negative effect on GRα-induced transactivation of GRE-driven promoters.