A Key Transcription Factor Family: Nuclear Receptors

In this chapter, a highly interesting family of ligand-inducible transcription factors, referred to as nuclear receptors, will be presented. Nuclear receptors serve since some 30 years as paradigms for many functional and structural aspects of transcription factors, such as the interaction with coactivator and corepressor proteins. Many of the 48 human members of the largest family of transcription factors in metazoans have the unique property to be specifically activated by small lipophilic ligands in the size of cholesterol (approximately 400 Da). Some of these ligands are known as endocrine hormones, such as estradiol and testosterone, while others are metabolites of dietary compounds, such as fatty acids and cholesterol. Both types of lipids are of large physiological impact in health and disease, such as metabolic control and the modulation of immunity. This made nuclear receptors especially attractive for both basic and applied research.