Multifaceted Regulation of Mineralocorticoid Receptor Transcriptional Activities

Project Summary Transcription factors (TFs) recognize specific DNA sequences and recruit coregulators including chromatin modification enzymes to direct gene expression. The human nuclear receptor (NR) family includes 48 TFs that play crucial roles in a number of biological processes including metabolism, reproduction, and inflammation.

The NRs share a highly disordered N-terminal domain (NTD), and two folded domains: a DNA-binding domain (DBD) and a C-terminal ligand binding domain (LBD), connected by a small unstructured hinge region. Despite numerous studies focusing on the individual LBD and DBD, how ligands elicit full-length NR activities remains

elusive with massive knowledge gaps in the roles of NTD and allostery between DBD and LBD. The long-term goal of the laboratory is to develop the molecular-level understanding of the mechanism underlying the NR transcriptional activity. We will use mineralocorticoid receptor (MR) as an exemplary member in this proposal.

MR is highly expressed in the renal distal nephron epithelial cells and plays critical roles in fluid and electrolyte homeostasis. It is also expressed in non-epithelial tissues such as heart, vasculature, brain, adipose and liver tissues. Overactivation of MR in these tissues leads to increased inflammation, fibrosis and oxidative stress.

MR antagonist have shown great promise as therapies for cardiovascular and renal disease. However, their development is severely lagging compared to others targeting MR homologs such as glucocorticoid, androgen and estrogen receptors. Detailed studies of each domain, including the least understood, intrinsically

disordered NTD, and how these domains cooperate with each other in the full-length MR is highly required for the deeper understanding of MR activity regulation. The focus of this proposal will be on: 1) determine how NTD and hinge region regulate MR transcription by forming biomolecular condensates and 2) determine how

the interdomain and intradomain allostery tune the MR-mediated transcription. An integration of biophysical approaches with structural biology and phase separation studies, as proposed here, is essential to decipher this highly dynamic and disordered system. While being fundamentally important to our understanding of MR

activity controlling gene transcription, our results can guide the future development of MR antagonist targeting various diseases caused by dysfunctional MR activities.