PARP1 inhibition suppresses and DNA-PKcs inhibition enhances chromosomal translocations. (A) The p5rE dual I-SceI translocation reporter system has 5′ and 3′ neo segments with splice donor (SD) and splice acceptor (SA) signals on chromosomes 14 and 17. After translocation NHEJ reconstitutes a functional neo on der[17], which can be quantified by clonal survival in G418. (B) p5rE cells were treated with the PARP1 inhibitor olaparib (3 μM), the DNA-PKcs inhibitor NU7441 (5 μM), or the DMSO vehicle as a control during and after translocation induction with I-SceI. Values are averages (± standard error of the mean [SEM]) for 3 or more determinations. (C) Olaparib does not alter expression of the transfected I-SceI. (D) NU7441 does not reduce survival duration of the p5rE cells, but olaparib decreases survival duration moderately. However, all results were normalized for survival in inhibitors.