Repurposing nuclear receptors for ligand-responsive liquid condensate formation and gene regulation

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.