Specificity: Specific for human histone H2AX. H2AX comprises approximately 2-25% of the histone H2A pool in mammalian cells. The extended C-terminal tail of H2AX contains a serine (Ser139) embedded in an conserved SQE motif, which is rapidly phosphorylated at sites of double strand breaks and stalled replication forks. Phosphorylated H2AX may serve to recruit other repair proteins to the site of DNA damage. H2AX has been implicated in both homologous recombination and nonhomologous end joining DNA repair pathways