Genome-wide binding potential and regulatory activity of the glucocorticoid receptor’s monomeric and dimeric forms

Abstract

A widely regarded model for glucocorticoid receptor (GR) action postulates that dimeric binding to DNA regulates unfavorable metabolic pathways while monomeric receptor binding promotes repressive gene responses related to its anti-inflammatory effects. This model has been built upon the characterization of the GRdim mutant, reported to be incapable of DNA binding and dimerization. Although quantitative live-cell imaging data shows GRdim as mostly dimeric, genomic studies based on recovery of enriched half-site response elements suggest monomeric engagement on DNA. Here, we perform genome-wide studies on GRdim and a constitutively monomeric mutant. Our results show that impairing dimerization affects binding even to open chromatin. We also find that GRdim does not exclusively bind half-response elements. Our results do not support a physiological role for monomeric GR and are consistent with a common mode of receptor binding via higher order structures that drives both the activating and repressive actions of glucocorticoids.

Point mutation I634A in the glucocorticoid receptor causes embryonic lethality by reduced ligand binding

“…Although a further reduction in dimerization in the double mutant cells compared to GR D/D could not be demonstrated, the double mutation led to another 50% (from 20% gene expression increase J o u r n a l P r e -p r o o f compared to controls to 10% gene expression increase) reduction the of gene induction capacity of GRE genes compared to GR D/D cells, which already showed only fraction of activity compared to GR wt/wt cells. These results are in agreement with the recently published study by Johnson et al (46), where an in-depth in vitro comparison of the GR wt/wt , GR D/D and GR D+L /D+L genotypes was performed. However, we found that GR L/L cells displayed a significant residual dimerization as well as only a 50% reduction on dimer mediated transcriptional activation as compared to GR wt/wt .…”

“…In GR D+L/D+L mutants, a Kd 2.5x lower compared to GR wt/wt was detected. These differences in ligand affinity remain unexplained, but they might suggest that the DBD dimerization provides a ligand-affinity lowering signal, while the LBD dimerization causes an opposite signal (Figure (46). Indeed, as the GR wt/wt and GR D/D behave normally in ligand binding and translocate to the nucleus, the differences in expression can only be explained by differences in DNA binding between both receptors.…”

The multivalency of the glucocorticoid receptor ligand-binding domain explains its manifold physiological activities

“…Our live-cell imaging studies have revealed that dimeric GR might be an intermediate state towards transcriptionally active tetramers bound to target DNA sequences (Presman et al, 2016;Paakinaho et al, 2019;Johnson et al, 2021), also in line with the current SPR results. Although more speculative, it is possible to generate tentative models of DNA-bound GR tetramers that satisfy the constraints derived from current structure-function information.…”

“…6B, arrowheads). Severely reduced genome-wide chromatin binding for GR mon has recently been shown (Johnson et al, 2021), and only a very small percentage of GR mon cells form visible arrays (Presman et al, 2016(Presman et al, , 2014. Interestingly, we did not detect any arrays in experiments with GR mon/Y545A (Fig.…”

The Role of Glucocorticoids in Inflammatory Diseases

“…These findings indicate that neither the beneficial nor the deleterious GC activities can be unequivocally assigned to one or the other molecular mechanism of the GR. A possible explanation for the ambiguous situation in GR dim mice is provided by the recent observation that the A458T mutation disrupts only one of the GR dimerization interfaces thus allowing some residual binding as dimers [ 195 ]. Otherwise, GR dim mice undoubtedly show a reduced transcriptional response [ 192 ], suggesting that a partial impairment of GR activity is sufficient to blunt anti-inflammatory GC effects [ 196 ].…”