ATRX is a member of the Snf2 family of helicase/ATPases, which contribute to the remodeling of the nucleosome structure in an ATP-dependent manner and facilitate the initiation of transcription and replication. Structurally, ATRX contains a PHD zinc finger motif. ATRX is regulated throughout the cell cycle, where it is differentially distributed within the nucleus. ATRX predominately associates with the nuclear matrix during interphase, while during mitosis, ATRXlocalizes with condensed chromatin. At the onset of the M phase, phosphorylation rapidly induces this redistribution of ATRX to the short arms of human acrocentric chromosomes. It then complexes explicitly with heterochromatin protein 1 α to mediate chromosomal segregation. Mutations in the ATRX gene correlate with a high incidence of severe X-linked form of syndromal mental retardation associated with α thalassemia or ATRX syndrome