C/EBP ? regulates gene expression in a variety of tissues including liver, adipose, lung and intestine. C/EBP ? uses a bipartite structural motif to bind DNA. Two protein chains dimerize through a set of amphipathic ? helices termed the leucine zipper. Highly basic polypeptide regions emerge from the zipper to form a linked set of DNA contact surfaces. C/EBP ? appears to function exclusively in terminally-differentiated, growth-arrested cells. Additional family members include C/EBP ?, C/EBP ?, C/EBP ? and C/EBP ?, all of which exhibit similar DNA-binding specificities and affinities to C/EBP ?. Furthermore, C/EBP ? and C/EBP ? readily form heterodimers both with each other as well as with C/EBP ?.