Ligand-independent activation of steroid receptors: New roles for old players

Steroid receptors are known as ligand-regulated transcription factors, but more and move evidence indicates that several steroid receptors can be acti vated in the absence of cognate hormone by agents that fall into three sepa rate groups: peptide growth factors, the neurotransmitter dopamine and othe r agents that activate cAMP-dependent protein kinase A, and the cyclins A a nd D1.