Figure 3. Mcl-1 is essential for DSB repair via HR in S/G₂ cells.

(A) Endogenous Mcl-1 was knocked out from H1299 using CRISPR/Cas9 system. (B) H1299 parental and H1299 Mcl1^–/– cells were treated with IR (0.5 Gy), followed by costaining with cyclin A and γ-H2AX antibodies immediately or after 7 hours. Cyclin A is a well-known S/G₂ marker; therefore, cyclin A–positive cells are considered as S/G₂-phase cells. Scale bar: 25 μm. The γ-H2AX foci per cell were determined by counting of at least 100 cells from each sample. Data represent the mean ± SD, n = 3 per group. ***P < 0.001, by 2-tailed t test. (C) H1299 parental and H1299 Mcl1^–/– cells were treated with IR (0.5 Gy), followed by costaining with cyclin A and Rad51 antibodies. Scale bar: 25 μm. The Rad51 foci per cell were determined by counting of at least 100 cells from each sample. Data represent the mean ± SD, n = 3 per group. ***P < 0.001, by 2-tailed t test.