**2.4 H2A phosphorylation assay**

MH7A cells were incubated in a chemiluminescence detection assay kit (Upstate, Charlottesville, Virginia, USA) and reacted with an anti-phospho-H2A.X (Ser139) followed by an anti-mouse-HRP conjugate. Phosphorylation of H2A.X at Ser139 was identified by staining with chemiluminescent HRP substrate LumiGLO, and signals were detected with a microplate luminometer (ARVO mx/light, Perkinelmer, Waltham, MA, USA).
