FIG 1.

Effect of BKRF4 on DSB signaling. (A) U2OS cells were transiently transfected with FLAG-BKRF4 expression plasmid, and then cells were treated for 2 h with etoposide (10 μg/ml for 53BP1 and FK2 foci and 1 μg/ml for γ-H2AX foci) to induce DNA damage. Cells were stained with antibody against FLAG and antibody against either 53BP1, conjugated ubiquitin (FK2), or γ-H2AX to mark DDR foci and then counterstained with DAPI. DDR foci were counted in 50 FLAG-positive and 50 FLAG-negative cells on the same slides. The distribution of the cell focus numbers for one experiment is shown in each cluster diagram. The bar graphs show the average focus values relative to FLAG-negative control (ctl) cells, with SDs and P values (*, 0.01 < P < 0.05; **, 0.001 < P < 0.01; ***, P < 0.001) from 3 independent experiments. (B) Same experiment as for panel A except that FLAG-BKRF4N and FLAG-BKRF4C expression plasmids were used. Scale bars = 10 μm.