Nuclear receptor belong to a superfamily of protein.Members of this family are characterized by similar three major structure region including a highly conserved DNA binding domain.Nuclear receptor bind to specific DNA sequence and control specific gene transcription.Recent data show that,in addtion to contacting to basal transcription factors,nuclear receptor inhibit or enhance transcription by recruiting the array of coactivator or corepressor.Coactivators are necessary for the efficient transcription.CBP/P300, SRC-1and SMRT are the main coactivators and corepressor found so far.