label: histone H2AXS139 kinase activity
label_lc: histone h2axs139 kinase activity
description: "Catalysis of the reaction: histone H2AX-serine (position 139) + ATP = histone H2AX-phosphoserine (position 139) + ADP. This reaction is the addition of a phosphate group to the serine residue at position 139 of histone variant H2AX."