Glucocorticoid Receptor Binding to Chromatin is Selectively Controlled by Coregulator Hic-5 and Chromatin Remodeling Enzymes [Signal Transduction]

The steroid hormone-activated glucocorticoid receptor (GR) regulates cellular stress pathways by binding to genomic regulatory elements of target genes and recruiting coregulator proteins to remodel chromatin and regulate transcription complex assembly. The coregulator Hydrogen peroxide-inducible clone 5 (Hic-5) is required for glucocorticoid (GC) regulation of some genes, but not others, and blocks regulation of a third gene set by inhibiting GR binding. How Hic-5 exerts these gene-specific effects, and specifically how it blocks GR binding to some genes but not others is unclear. Here we show that site-specific blocking of GR binding is due to gene-specific requirements for ATP-dependent chromatin remodeling enzymes. By depletion of eleven different chromatin remodelers, we found that ATPases CHD9 (Chromodomain Helicase DNA binding protein 9) and BRM (Brahma homologue, product of the SMARCA2 gene) are required for GC-regulated expression of the blocked genes, but not for other GC-regulated genes. Furthermore, CHD9 and BRM were required for GR occupancy and chromatin remodeling at GR binding regions associated with blocked genes, but not at GR binding regions associated with other GC-regulated genes. Hic-5 selectively inhibits GR interaction with CHD9 and BRM, thereby blocking chromatin remodeling and robust GR binding at GR binding sites associated with blocked genes. Thus, Hic-5 regulates GR binding site selection by a novel mechanism, exploiting gene-specific requirements for chromatin remodeling enzymes to selectively influence DNA occupancy and gene regulation by a transcription factor.

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