Figure 4. DNA2/EXO1-depleted U2OS cells accumulate DSBs and broken chromosomes after CPT or cisplatin replication inhibition. (A) Pulse-field gel electrophoresis shows markedly higher amounts of unrepaired DNA in DNA2/EXO1-depleted cells than in the DNA2 or EXO1-depleted cells. (B) After the simultaneous depletion of DNA2 and EXO1, the number of breaks per metaphase spread observed in the absence of DNA damage (DMSO) increases upon exposure to cisplatin or to CPT. At least 100 cells were counted in each independent experiment. See Experimental Procedures and Supplemental Material for details. CDDP, cisplatin.