SLFN11 disruption partially reverses drug sensitivity in FANCD2^−/−HAP1 cells. (A) FANCD2 and SLFN11 expression in knockout HAP1 cell lines. WT, wild type. (B) Cell growth curve of the indicated knockout HAP1 cell lines. Fold proliferation was calculated in 3 independent experiments. Means ± standard error of the mean (SEM) are shown. (C) Clonogenic cell survival assays in response to indicated doses of various genotoxic agents. MMC, mitomycin C. Means ± SEM of 3 independent experiments are shown. (D) A schematic of SLFN11 protein structure. Positions of the mutations in the ATPase domain are shown. (E) Expression of DOX-induced SLFN11 wild-type (WT) or ATPase dead mutant (Mut) protein in the FANCD2^−/−SLFN11^−/− HAP1 knockout cell line. Lentivirally transduced cells were selected and treated for 48 hours with doxycycline (DOX). (F) Clonogenic cell survival assays in FANCD2^−/−SLFN11^−/− cells transduced with SLFN11 wild-type or an ATPase dead mutant. DOX (2 μg/mL)-treated cells were exposed to the indicated doses of MMC or formaldehyde for 24 hours, and colonies were counted 5 to 7 days later. Means ± SEM of 3 independent experiments are shown.