MDFIC alters the GR transcriptome in A549 cells

Glucocorticoids are primary stress hormones that regulate many physiological processes, and synthetic derivatives of these molecules and are widely used in the clinic. The cellular response to glucocorticoids is remarkably diverse; however, the molecular factors that govern tissue specificity are poorly understood. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR). To discover new proteins that interact with GR and modulate its function, we performed a yeast 2 hybrid assay using as bait the hinge region of GR. The MyoD family inhibitor domain-containing (MDFIC) protein was identified as a binding partner for GR. To investigate the function of the GR-MDFIC interaction, we performed a genome-wide microarray in intact and MDFIC deficient A549 cells that were treated with the synthetic glucocorticoid Dexamethasone (Dex). A large cohort of genes was differentially regulated by GR depending on the presence or absence of MDFIC. These findings identify a new binding partner for cytoplasmic GR that modulates the receptor transcriptome and contributes to the tissue specific actions of glucocorticoids. A549 cells were transfected with NTC siRNA or MDFIC siRNA. Cells were harvested the day after transfection and re-plated at appropriate tissue culture densities. Seventy-two hours post-transfection, cells were stimulated with either vehicle (control) or 100nM Dex for 6 hours. Prior to Dex treatment, cells were cultured overnight in medium supplemented with 10% charcoal-stripped FBS. Total RNA was harvested for microarray analysis using the RNeasy Mini Kit and RNase-Free DNase Kit (Qiagen) from 3 biological replicates of vehicle-treated NTC cells, Dex-treated NTC cells, vehicle-treated MDFIC knockdown cells, and Dex-treated MDFIC knockdown cells.