FANCD2 contains a putative CUE ubiquitin-binding domain. (A) Schematic of the FANCD2 protein indicating the amino terminus CUE domain, the PCNA-interaction motif (PIP), and the carboxy terminus EDGE motif. (B) A ClustalW alignment of the amino terminus of FANCD2 with several known CUE domains. (C) A ClustalW alignment of the amino terminus of FANCD2 from several species demonstrates high conservation of this region. Asterisks indicate highly conserved amino acid residues known to be important for noncovalent interaction with ubiquitin.