CCAAT-enhancer-binding proteins (or C/EBPs) is a family of transcription factors composed of six members, named from C/EBPα to C/EBPζ. They promote the expression of certain genes through interaction with their promoters. Once bound to DNA, C/EBPs can recruit so-called co-activators (such as CBP) that in turn can open up chromatin structure or recruit basal transcription factors.

C/EBP proteins interact with the CCAAT (cytosine-cytosine-adenosine-adenosine-thymidine) box motif, which is present in several gene promoters. They are characterized by a highly conserved basic-leucine zipper (bZIP) domain at the C-terminus. This domain is involved in dimerization and DNA binding, as are other transcription factors of the leucine zipper domain-containing family (c-Fos and c-jun). The bZIP domain structure of C/EBPs is composed of an α-helix that forms a "coiled coil" structure when it dimerizes. Members of the C/EBP family can form homodimers or heterodimers with other C/EBPs and with other transcription factors, which may or may not contain the leucine zipper domain. The dimerization is necessary to enable C/EBPs to bind specifically to DNA through a palindromic sequence in the major groove of the DNA. C/EBP proteins also contain activation domains at the N-terminus and regulatory domains.

These proteins are found in hepatocytes, adipocytes, hematopoietic cells, spleen, kidney, brain, and many other organs. C/EBP proteins are involved in different cellular responses, such as in the control of cellular proliferation, growth and differentiation, in metabolism, and in immunity. Nearly all the members of the C/EBP family can induce transcription through their activation domains by interacting with components of the basal transcription apparatus. (C/EBPγ is an exception that lacks a functional transcriptional activation domain.) Their expression is regulated at multiple levels, including through hormones, mitogens, cytokines, nutrients, and other factors.

This protein is expressed in the mammalian nervous system and plays a significant role in the development and function of nerve cells. C/EBPβ plays a role in neuronal differentiation, in learning, in memory processes, in glial and neuronal cell functions, and in neurotrophic factor expression.

The C/EBPα, C/EBPβ, C/EBPγ and C/EBPδ genes are without introns. C/EBPζ has four exons; C/EBPε has two, which lead to four isoforms due to an alternative use of promoters and splicing. For C/EBPα and C/EBPβ, different sizes of polypeptides can be produced by alternative use of initiation codons. This is thought to be due to weak ribosome scanning mechanisms. The mRNA of C/EBPα can transcribe into two polypeptides. For C/EBPβ, three different polypeptides are made: LAP* (38 kDa), LAP (35 kDa) and LIP (20 kDa). The most translated isoform is LAP, then LAP* and LIP. LIP can act as an inhibitor of the other C/EBPs by forming non-functional heterodimers.

C/EBPβ function is regulated by multiple mechanisms, including phosphorylation, acetylation, activation, autoregulation, and repression via other transcription factors, oncogenic elements, or chemokines. C/EBPβ can interact with CREB, NF-κB, and other proteins, leading to a trans-activation potential.

Phosphorylation of C/EBPβ can have an activation or a repression effect. For example, phosphorylation of threonine 235 in human C/EBPβ, or of threonine 188 in mouse and rat C/EBPβ, is important for C/EBPβ trans-activation capacity. Phosphorylation(s) of C/EBPβ in its regulatory domain can also modulate its function.

It was shown in C. elegans that multiple cis elements of cebp-1 mRNA 3'UTR interact with mak-2 to upregulate expression of CEBP-1 in neuronal development.