Chromodomains participate in the recognition of lysine-methylated histone tails and nucleic acids. The CHD1 protein, named for its chromo-domain, ATPase helicase-like domain and DNA-binding domain, functions as an ATP-utilizing chromatin assembly factor. Unlike HP1 and Polycomb proteins that use single chromodomains to bind to their respective methylated Histone H3 tails, the two chromodomains of CHD1 cooperate to associate with one methylated H3 tail. Unique inserts within chromodomain 1 of CHD1 block the expected site of H3 tail binding seen in HP1 and Polycomb, and instead direct H3 binding to a groove at the interchromodomain junction. The human CHD1 gene maps to 5q21.1, and encodes a 1,709 amino acid deduced protein that shares 95.5% identity with the 1,711 amino acid mouse Chd1 polypeptide.