H2A histone family member X (H2AX)

H2A histone family member X (H2AX) is a variant of the H2A core histone involved in chromatin structure and function[1][3]. It plays a central role in the cellular response to DNA double-strand breaks (DSBs): upon DSB induction, H2AX is rapidly phosphorylated at serine 139 (γH2AX) by PI3 kinase family members such as ATM, ATR, or DNA-PK[1]. This phosphorylation event signals the presence of DNA damage, recruits repair proteins to the site of DNA lesions, and is vital for the maintenance of genomic stability[1][2][3]. The presence of γH2AX foci is widely used as a sensitive biomarker for monitoring DNA damage in cells[1][3]. H2AX contributes to nucleosome formation, chromatin remodeling, cell cycle arrest following DNA damage, and efficient DSB repair; its dysfunction is implicated in cancer and genome instability syndromes[1][3]. No direct therapeutic drugs are currently known to target H2AX, but its phosphorylated form is a key biomarker and research tool in assessing DNA damage and repair efficacy[1][3].

Other names

H2A.XH2AFXH2A/Xvariant histone H2A.XγH2AX (phosphorylated form)