Abstract: The present invention relates to novel nuclear receptor ERR?3. Although ERR?3 itself lacks a DNA binding domain, it comprises the function of enhancing the transcriptional activation function of arbitrary nuclear receptors, such as ERR, ER, or TR. Moreover, the present inventors found that, like ERR?3, the known proteins ERR?1 and ERR?2 also comprise the function of enhancing the transcriptional activation function of other nuclear receptors. Thus, the present invention provides methods for evaluating the regulatory function of these ERR? subtypes in enhancing the transcriptional activation function of other nuclear receptors, and screening methods based on these evaluation methods.

Abstract: The present invention relates to the novel isoforms, RXR?2 and RXR?3, of nuclear receptor RXR?. Unlike known isoform RXR?1, the transcriptional activation functions of RXR?2 and RXR?3 are augmented by SRC-1. The present invention provides methods for evaluating the function of regulating augmentation by co-activators of these RXR? isoforms, and screening methods based on these evaluation methods. By controlling the interaction between isoforms and co-activators, transcription-controlling activity can be regulated in an isoform-specific manner.