The Ligand Binding Domain Controls Glucocorticoid Receptor Dynamics Independent of Ligand Release

Abstract

Ligand binding to the glucocorticoid receptor (GR) results in receptor binding to glucocorticoid response elements (GREs) and the formation of transcriptional regulatory complexes. Equally important, these complexes are continuously disassembled, with active processes driving GR off GREs. We found that cochaperone p23-dependent disruption of GR-driven transcription depended on the ligand binding domain (LBD). Next, we examined the importance of the LBD and of ligand dissociation in GR-GRE dissociation in living cells. We showed in fluorescence recovery after photobleaching studies that dissociation of GR from GREs is faster in the absence of the LBD. Furthermore, GR interaction with a target promoter revealed ligand-specific exchange rates. However, using covalently binding ligands, we demonstrated that ligand dissociation is not required for receptor dissociation from GREs. Overall, these studies showed that activities impinging on the LBD regulate GR exchange with GREs but that the dissociation of GR from GREs is independent from ligand dissociation.

We thank Marc Diamond, Abigail Kroch, Fred Schaufele, and Alex So for reviewing the manuscript and Samantha Cooper for computational assistance. Imaging was carried out in the Fluorescence Imaging Facility, Laboratory of Receptor Biology and Gene Expression, National Cancer Institute.

S.H.M. is supported by a postdoctoral fellowship from the Leukemia and Lymphoma Society. This work is supported by grants from the NIH to K.R.Y. and in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research.