SLX4IP is involved in ICL repair. (A) Results of clonogenic survival assays conducted with HEK293A-WT and SLX4IP-KO cells exposed to DNA damage-inducing agents (mitomycin C [MMC], campothecin [CPT], ultraviolet [UV] radiation, or ionizing radiation [IR]). For each cell line, the viability of untreated cells was defined as 100%. Data are presented as the mean ± standard error of the mean (SEM; n = 3). (B and C) HEK293A-WT, SLX4IP-KO, XPF-KO and MUS81-KO cells were treated with the indicated concentrations of MMC for 24 h or were nontreated (NT). Cells were collected and fixed with 70% ethanol before fluorescence-activated cell sorting (FACS) analysis of the cell-cycle distribution under different treatment conditions. The mean percentages of cells in the G2/M phase from three independent repeats of FACS are shown. The results were compared statistically with those for untreated cells. Statistical analysis was performed using the Student's t-test. **P < 0.01, ***P < 0.001, ns: not significant. P values <0.05 were considered statistically significant. (D) Immunostainings of SLX4, SLX4IP and γH2AX proteins performed following UV laser-induced DNA damage with the indicated antibodies. KO, knockout; WT, wild type.