The CCAAT-binding factor (CBFB/NF-YA) is a mammalian transcription factor that binds to a CCAAT motif in the promoters of a wide variety of genes, including type I collagen and albumin [<cite idref="PUB00002598"/>]. The factor is a heteromeric complex of A and B subunits, both of which are required for DNA-binding [<cite idref="PUB00004401"/>]. The subunits can interact in the absence of DNA-binding, conserved regions in each being important in mediating this interaction. <p>The B subunit contains a region of similarity with the yeast protein HAP2 [<cite idref="PUB00004731"/>]. For the B subunit it has been suggested that the N-terminal portion of the conserved region is involved in subunit interaction and the C-terminalregion involved in DNA-binding [<cite idref="PUB00002769"/>].</p>