Figure 1: Foci growth of phosphorylated H2AX in replicative senescence. (a) Visualization of phosphorylated H2AX foci (green) at the different PDLs indicated by the numbers. Nuclear counterstain was performed with PI (red). (b) Induction frequency of senescent cell (closed circle), H2AX phosphorylation (closed triangle), and large foci formation (open triangle). At least 300 cells and 100 cells were analyzed for senescent induction and foci diameter, respectively. Statistical analysis of the frequency between SA-β-gal (+) and large foci (+) was performed by Welch’s test. (* ) (c) Each Immuno-FISH image represented a cell with phosphorylated H2AX foci (red) in the absence (a) or the presence (b) of colocalization with telomere FISH signal (green). Arrowhead in (b) represents the phosphorylated H2AX focus accompanied with telomere FISH signal. (d) The frequency of cells in which large foci were detected with (+) or without (−) telomere signal. The data was analyzed with the cells detected large foci in both PDLs of 21 (closed bar) and of 64 (open bar (b)). At least 100 cells were investigated in both PDLs. (e) Colocalization of phosphorylated H2AX (green) and phosphorylated ATM (red) in replicative senescence. Nuclear counterstain was performed with DAPI (blue).