Brand: Merck Description As a member of the histone H2A family, histone H2A.x (H2A.x) is a variant histone H2A which replaces conventional H2A in a subset of nucleosomes. H2A.x is involved in the DNA repair of double-strand breakage (DSB) damage on nuclear DNA. After a double strand DNA break, H2A.x is rapidly phosphorylated at serine 139 by ATM kinase and becomes gamma-H2AFX. This phosphorylation step can extend up to several thousand nucleosomes from the actual site of the DSB and may mark the surrounding chromatin for recruitment of proteins required for DNA damage signaling and repair. As a part of posttranslational modifications during apoptosis caused by severe DNA damage, high expression of phosphorylated H2A.x is considered as an accurate indicator of apoptosis.
