Burd CJ, Ward JM, Davis VJ, Kissling GE, Phadke D, Shah RR, Archer TK
Steroid hormone receptors initiate a genetic program tightly regulated by the chromatin environment of the responsive regions. Using the glucocorticoid receptor (GR) as a model factor for transcriptional initiation, we classified chromatin structure through Formaldehyde Assisted Isolation of Regulatory Elements (FAIRE). We looked at dynamic changes in FAIRE signals during GR activation specifically at regions of receptor interaction. We found a distribution of GR responsive regions with diverse responses to activation and chromatin modulation. The majority of GR binding regions demonstrate increases in FAIRE signal in response to ligand. However, the majority GR responsive regions shared a similar FAIRE signal in the basal chromatin state, suggesting a common chromatin structure for GR recruitment. Supporting this notion, global FAIRE-seq data indicated an enrichment of signal surrounding the GR binding site prior to activation. Brg-1 knockdown showed response element specific effects of ATPase-dependent chromatin remodeling. FAIRE induction was universally decreased by Brg-1 depletion, but to varying degrees in a target specific manner. Taken together, these data suggest classes of nuclear receptor response regions that react to activation through different chromatin regulatory events and identify a chromatin structure that classifies the majority of response elements tested.