label: histone H2AS121 kinase activity
label_lc: histone h2as121 kinase activity
description: "Catalysis of the reaction: histone H2A-serine (position 121) + ATP = histone H2A-phosphoserine (position 121) + ADP. This reaction is the addition of a phosphate group to the serine residue at position 121 of histone H2A."