The actions of lipophilic hormones, including steroids, retinoids, thyroid
hormone and vitamin D,, are mediated through a conserved superfamily of nuc
lear receptor proteins that function as ligand-regulated, DNA-binding trans
criptional activators in the chromatin environment of the nucleus. The liga
nd-dependent transcriptional activity of nuclear receptors is enhanced by v
arious cofactors that remodel chromatin, acetylate nucleosomal histones and
contact the basal transcriptional machinery. The current challenge is to u
nderstand the mechanistic details of how interactions among these factors e
nhance transcription of hormone-regulated genes assembled into chromatin. C
urrent biochemical and cell-based methods are providing some important clue
s.