Liver-specific Liver-specific Glucocorticoid enhancer enhancer inducible cAMP-regulation enhancer Promoter

Fig. 18 Shown are the regulatory elements characterized so far, which control the transcription of the tyrosine aminotransferase (TAT) gene. The TAT gene may be induced either by glycocorticoids or by cyclic adenosine monophosphate (cAMP), which activates the protein kinase A. All distances are given in kilobases (kb) and refer to the starting point of the TAT gene transcription (arrow). mediated by cell-cell contacts play an important role. Furthermore, hormonal signals coordinate differentiation processes at the level of the organism. A close relation between signal transduction and cell-type-specific transcriptional control is exemplified by the tyrosine aminotransferase (TAT) gene which is expressed exclusively in liver cells and which is switched on briefly after birth. This switch is part of a terminal differentiation process by which the liver acquires gluconeogenic capacity as a response to specific metabolic requirements of the newborn organism.