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Repurposing nuclear receptors for ligand-responsive liquid condensate formation and gene regulation
Erik Rihtar1, Tina Fink1,2, Filip Ivanovski1,2
1Department of Synthetic Biology and Immunology, National Institute of Chemistry, Ljubljana, Slovenia.
Abstract:
Cells regulate processes through protein interaction networks. Most chemically induced dimerization (CID) systems respond to exogenous molecules, limiting integration with endogenous signaling. Here, we repurpose nuclear receptor (NR) ligand-binding domains (LBDs) and coactivators to develop hormone- or clinically approved drug-responsive CIDs. Using the LBDs of TRβ, VDR, RARγ, ERβ, and GR2 with a TIF2 coactivator peptide, we constructed CIDs responsive to triiodothyronine, vitamin D, retinoic acid, estrogen, cortisol, and their antagonists. These CIDs enable two-input transcriptional switches for gene regulation. Furthermore, we design hormone-responsive liquid-liquid phase-separated (LLPS) condensates that strongly amplify transcription when exceeding a critical interaction threshold. These functional LLPS condensates provide a tunable platform for transcriptional control with up to several hundred-fold activation. Our findings offer an approach for integrating synthetic biology with physiological signaling, advancing applications in gene circuits, biosensing, and therapeutics through ligand-controlled LLPS formation.
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