DMSR only occurs in G0 or G1 cells. (A) Microtubule regrowth assay was performed in G0 cells after bleomycin treatment. Microtubules (green) were stained with anti–β-tubulin antibody. Scale bar, 20 µm. (B) Quantitation of microtubule length after bleomycin treatment in G0 cells as in A was shown (n > 50). (C) The kinetics of DNA damage repair in bleomycin-treated cells were determined by 53BP1 foci formation (n > 100). (D) Quantitation of microtubule length in G0 cells after IR is shown (n > 50). (E) DMSR happens in G1 but not in S phase. Quantitation of microtubule length is shown (n > 50). The detailed procedure is shown in Fig. S2 B. (F) Microtubule regrowth assay was performed in asynchronized cells after IR. Cells were costained with anti–β-tubulin (green) and anti–cyclin A (red) antibodies. White arrowheads indicate cyclin A–positive cells and red arrowheads indicate cyclin A–negative cells. Scale bar, 20 µm. (G) Quantitation of microtubule length in cyclin A–negative and cyclin A–positive cells is shown (n > 50). ****, P < 0.0001; ***, P < 0.001; **, P < 0.01; *, P < 0.05; ns, not significant. MT, microtubule; UT, untreated.