The Histone H2A.X Colorimetric Cell-Based ELISA Kit provides a lysate-free, convenient, and high-throughput approach for sensitive detection of HistoneH2A.X protein expression profile in cells. The kit can be used for measuring the relative amounts of HistoneH2A.X in cultured cells as well as screening for the effects that various treatments, inhibitors (ie siRNA or chemicals), or activators have on HistoneH2A.X.