Nuclear receptor binding factor-1 (NRBF-1), a protein interacting with a wide spectrum of nuclear hormone receptors.

To identify the proteins which may modulate the functions of peroxisome proliferator-activated receptor (PPAR), a rat liver cDNA library was screened by a yeast two-hybrid system, using the mouse PPARalpha as a bait. A protein named nuclear receptor binding factor-1 (NRBF-1) was identified, which interacts not only with PPARalpha, but also with various nuclear hormone receptors in the presence of the respective ligands. Both the hinge and ligand-binding domains of PPARalpha are required for the interaction. NRBF-1 seems to be translocated to the nucleus by a piggyback mechanism, together with PPARalpha. NRBF-1 has a significant homology to the yeast protein MRF1, a putative transcription factor regulating the expression of mitochondrial respiratory proteins. NRBF-1 might be another type of nuclear receptor co-operator.