Nuclear receptors (NRs) are ligand-regulated, DNA-binding transcription factors that function in the chromatin environment of the nucleus to alter the expression of subsets of hormone-responsive genes. It is clear that chromatin, rather than being a passive player, has a profound effect on both transcriptional repression and activation mediated by NRs. NRs act in conjunction with at least three general classes of cofactors to regulate transcription in the context of chromatin: (a) chromatin remodelers; (b) corepressors; and (c) coactivators, many of which have distinct enzymatic activities that remodel nucleosomes or covalently modify histones (. acetylases, deacetylases, methyltransferases, and kinases)
