ATAD5 (ATPase family, AAA domain containing 5), also known as chromosome fragility-associated gene 1 protein, FRAG1 or ELG1, is a 1,844 amino acid nuclear protein that is involved in the DNA damage response and belongs to the AAA ATPase family. Existing as two alternatively spliced isoforms, ATAD5 interacts with Rad9 in growing cells where it assists in interactions between Rad9 and Bcl-2.