CNOT6 contains 575 amino acids. RT-PCR ELISA detected variable expression in all fetal and adult tissues and specific brain regions examined. Highest expression was in adult brain, testis, ovary, spinal cord, and caudate nucleus, and lowest expression was in pancreas and spleen. CNOT6 augments the ligand-dependent transcriptional activation of a wide variety of nuclear receptors, including RARA, THRA, RXRA, ESR1, and GCCR, through an NIF1 coactivator complex. siRNA-mediated silencing of endogenous CNOT6 resulted in a marked decrease in nuclear receptor activation as well as attenuated stimulation of RARA target genes, including SOX9 and HOXA1. siRNA knockdown of NIF1, with which CNOT6 associates in vivo, blocked the ligand-dependent potentiating effect of CNOT6.