Other all-alpha-helical DNA-binding domains Heteromeric CCAAT-binding factors Class Class description: The heteromeric CCAAT-binding factor known from mammalian systems is NF-Y (CBF, CP1), a homolog of yeast HAP2/3/4. Like the latter, it is a heterotrimeric complex of which all three subunits NF-YA, NF-YB and NF-YC are required for binding to the CCAAT-element on the DNA. NF-YB and NF-YC both exhibit a histone-fold domain, showing some homology with histones H2B and H2A, respectively. These regions are required for heterodimerization, which is followed by docking of NF-YA. Modeling of the NF-Y complex and its binding to DNA according to the homology with histone and NC2 complexes suggests that the heterotrimeric complex provides an alpha-helically folded interface to interact with the DNA. Contribution of some loop structures is also conceivable. Upon binding through major and minor groove contacts, the NF-Y complex induces considerable bending of the DNA. (PMID 12401788)