Acts as a coactivator during transcriptional activation of nuclear genes related to mitochondrial biogenesis and cell growth. Involved in the transcription coactivation of CREB and NRF1 target genes (By similarity). Interacts with CREB1 and NRF1. Colocalizes with NRF1. Expressed in liver, heart, skeletal muscle, kidney and white and brown adipose tissues. Up-regulated by serum (at protein level). Up-regulated by serum. Up-regulated weakly in brown adipose tissue by exposure of animals to cold.