Steroid and thyroid hormones and retinoic acid regulate a complex array of gene expression activity via intracellular receptor transcription factors belonging to the ligand dependent nuclear receptor superfamily. Adding to the complexity of function of these transcription factors are associated proteins known as coactivators and corepressors which, as their names suggest, enhance or depress transcriptional activity of the nuclear receptor with which they associate. SRC3 is a nuclear receptor coactivator that interacts with nuclear hormone receptors to enhance their transcriptional activator functions. The protein has histone acetyltransferase activity and recruits p300/CBP-associated factor and CREB binding protein as part of a multisubunit coactivation complex. This protein is initially found in the cytoplasm but is translocated into the nucleus upon phosphorylation. Two transcript variants encoding different isoforms have been found for this gene. In addition, a polymorphic repeat region is found in the C-terminus of the encoded protein.