FIGURE 6.

ATM activation is proficient in Kdm4b-overexpressing cells. U2OS cells were plated on glass coverslips and transfected with Kdm4b-EGFP. 24 h after transfection the plated cells were exposed to 2 Gy γ-irradiation and then fixed at 30 and 60 min recovery. Indirect immunofluorescence was used to stain phosphorylated ATM. Nuclei were counterstained with DAPI. Images were obtained and processed to ensure quantitative micrographs. Exposure times were held constant, and the resulting images were scaled identically. B, γH2AX foci formation 5 min after 2 Gy γ-irradiation as a readout for ATM activation. Kdm4b-EGFP cells were proficient at the formation of ATM-dependent γH2AX foci. C, shown is quantification of γ-irradiation-induced pATM foci in Kdm4b-EGFP-positive and -negative cells. Overexpression of Kdm4b-EGFP resulted in no significant change in pATM foci numbers. n.s., not significant.