Fig 1: PARPi-dependent MMEJ increase depends on both NHEJ and MMEJ.(A) MMEJ quantification using reporter and experimental timeline from Figure 1A–B in HT1080 cells following olaparib (5 μm), DNA-PKcsi (NU7441, 1 μm), or both. Values are normalized to each cell line DMSO. (B) Immunoblot of 53BP1 and histone H3 in parental HT1080 cells and isogenic TP53BP1-KO cells. (C) MMEJ quantification in HT1080 parental cells and indicated isogenic TP53BP1-KO cells. Values are normalized to wild-type DMSO. Drug used was olaparib (5 μm). (D-E) Immunoblot of Actin, WRN (D), and EXO1 (E) in parental HT1080 cells and isogenic WRN-KO (D) and EXO1-KO (E) cells. (F-G) MMEJ quantification in HT1080 parental cells and indicated isogenic WRN-KO (F) or EXO1-KO clones (G). Values are normalized to wild-type DMSO. Drug used was olaparib (5 μm). (H) MMEJ quantification in PEO1-OR cells following olaparib (5 μm), DNA-PKcsi (NU7441, 2.5 μm), or combo.Statistical analyses for (A, C, F-H). Data represent three (A, C, F, H) or four (G) independent experiments, each the average of three technical replicates. Data are mean ± SEM. Statistical test, one way ANOVA with multiple comparison correction. ns: non-significant, *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001.