GR alleles used in this study. Rat GRα, the major isoform of GR, is a 795 amino acid protein with a modular structure typical of nuclear receptors: an N-terminal activation function 1 (AF1) domain, a DNA-binding domain (DBD), and a C-terminal ligand binding domain (LDB), which contains the activation function 2 (AF2) domain. We used mutations of GRα in AF1 (30iiB); AF2 (E773R); the dimerization interface of the DBD (A477T); and a minor isoform GRγ, which bears a single amino acid (arginine) insertion at position 471 in GRα as a result of alternative splicing. Domain boundaries are approximate, based on functional assays. Western blots show that GR was expressed at similar levels in all cell lines, which were similar to the level of endogenous GR found in the lung adenocarcinomic human alveolar basal epithelial cell line A549.