Description
The transcription factor C/EBP Alpha (CCAAT-enhancer binding protein) is a heatstable, sequence-specific DNA-binding protein first purified from rat liver nuclei that binds avidly to several different cis-regulatory DNA sequences commonly associated with viral and cellular genes transcribed by RNA polymerase II. C/EBP Alpha regulates gene expression in a variety of tissues including liver, adipose, lung and intestine. C/EBP Alpha uses a bipartite structural motif to bind DNA. Two protein chains dimerize through a set of amphipathic Alpha helices termed the leucine zipper. Highly basic polypeptide regions emerge from the zipper to form a linked set of DNA contact surfaces. C/EBP Alpha appears to function exclusively in terminally differentiated, growth-arrested cells. Additional family members include C/EBP beta, C/EBP gamma, C/EBP delta and C/EBP epsilon, all of which exhibit similar DNA-binding specificities and affinities to C/EBP Alpha. Furthermore, C/EBP beta and C/EBP delta readily form heterodimers both with each other as well as with C/EBP Alpha