Gen1 mutation increased the sensitivity of Eme1PB/+ MEFs to DNA-damaging reagents. WT, Gen1PB/PB, Eme1PB/+, and Gen1PB/PB; Eme1PB/+ MEF cells were subjected to doses of CPT (A), Etoposide (B), MMC (C), MMS (D), and HU (E) as indicated. The survival rate of the cells was quantified 1 week later. Compared with Eme1PB/+ MEF cells, Gen1PB/PB; Eme1PB/+ MEF cells were more sensitive to CPT (A), Etoposide (B), and MMC (C). (F) Real-time RT PCR results of Gen1 in the four cell lines. (G) Real-time RT-PCR results of Gen1 in the four cell lines. Data are presented as mean ± SEM. *, p < 0.05; **, p < 0.01, ***, p < 0.001; unpaired t test. CPT, camptothecin; HU, hydroxyurea; MMC, mitomycin C; MMS, methyl methanesulfonate.