Fig. 4
DDR signaling activates the G2/M checkpoint to induce G2 arrest. A Western blot. Cells were treated by 100 nM CBG for the indicated times. A time-dependent, rapid increase in phosphorylation of CDC25C and p53, as well as total protein levels of p53 and p21Cip1/Waf1, was induced. B, C Analysis of cell cycle by flow cytometry. Cells were treated by 100 nM CBG for 24 or 48 h. Treatment by 100 nM CBG caused a progressive accumulation of cells in the 4n group, a rapid decrease in the size of the 2n population and no significant change in the size of the 2n-4n population. The subG1 population (cells with < 2n DNA) increased continuously. Some cells with > 4n DNA were generated during the first 24 h but disappeared after 48 h of treatment (B), they were excluded from quantitative measurements (C). n.s.: not significant, *: p < 0.05, **: p < 0.01, ***: p < 0.001, ****: p < 0.0001 vs vehicle control (n = 3)