Brand: Merck Description Histone H2A.X is a variant of histone H2A, and is similarly associated with genomic DNA. However, histone is structurally different from other members of the H2A family in possessing a C-terminal tail that contains the Ser139 residue that is phosphorylated in response to breaks in double-stranded DNA. The phosphorylation of H2A.X is a rapid process that is mediated by ATM/ATR proteins.
