Background: NRBF2 (nuclear receptor binding factor-2) was originally identified in a yeast two-hybrid screen for factors that interact with the peroxisome proliferator-activated receptor alpha (PPARalpha). In a second study, NRBF2 was also identified in a screen of a keratinocyte cDNA library and named COPR (comodulator of PPAR and RXR). In this study, NRBF2 was proposed to function as a modulator of transcriptional activity that functions to decrease rather than completely repress nuclear-receptor mediated gene expression.