Nucleic acids encoding NRIF3 are described. Polypeptides having amino acid sequences of NRIF3 proteins are also provided. A method is also provided for isolating and cloning NRIF3 cDNA. NRIF3 is useful in development/implementation of high throughput screens to identify novel thyroid hormone receptor (TR) and retinoid X receptor (RXR) agonists and antagonists. Methods are also provided for identifying compounds that directly interfere with the interaction of NRIF3 and TR or RXR. Finally, therapies based on modulation of NRIF3 activity are disclosed.