Heterochromatin is refractory to γ-H2AX modification in yeast and mammals

Wildtype mouse embryo fibroblasts were treated with the histone deacetylase inhibitor trichostatinA 8 hours before being incubated with the radiomimetic drug neocarzinostatin (NCS) for 1hour prior to being fixed and immunolabeled against the phosphorylated form of histone H2AX (red, Alexa 546 conjugated secondary antibody) and co-stained with DAPI (blue). A stack of confocal optical slices was captured through the depth of the nucleus (Z-axis) using a 63x Plan-Apochromat (N.A. 1.4) objective lens, an optical slice thickness of 800nm, a Z-step size of 200nm, and X-Y pixel size of 70nm.