Figure 2From: Soluble histone H2AX is induced by DNA replication stress and sensitizes cells to undergo apoptosisOverexpression of H2AX but not H2A leads to apoptotic cell death and stimulates apoptosis. (A) Quantification of apoptotic U-2 OS cells following transient overexpression of empty GFP vector, GFP-H2AX or GFP-H2AX-SA for 24 h. Only transfected, GFP-positive cells were counted. Apoptosis was scored based on the nuclear morphology. Each bar indicates mean + standard error of at least three independent experiments with at least 100 cells counted per experiment. (B) Fluorescence microscopic analysis of U-2 OS cells transiently transfected with empty GFP vector (control), GFP-H2AX or GFP-H2AX-S139A for expression of γ-H2AX. Note the negative staining for γ-H2AX of a cell transfected with mutant H2AX-S139A. Nuclei stained with DAPI. Scale bar indicates 10 μm. (C) Quantification of apoptotic cells in U-2 OS populations stably transfected with empty GFP vector, GFP-H2AX or GFP-H2AX-S139A and treated with 10 μM aphidicolin for 24 h. Each bar indicates mean + standard error of at least three independent experiments with at least 100 cells counted per experiment. (D) Fluorescence microscopic analysis of a U-2 OS cell transiently transfected with myc-H2A and stained with an anti-myc-tag antibody. Nucleus stained with DAPI. Scale bar indicates 10 μm. (E) Quantification of apoptotic U-2 OS cells following transient overexpression of empty myc-tag vector (control) or myc-H2A for 24 h. Each bar indicates mean + standard error of at least three independent experiments with at least 100 cells counted per experiment.Back to article page