Fig. 4: Physiological role of ERCC6L2 in avoiding loss of sequence.

a Competition assay monitoring the ratio of RPE1 TP53^−/− cells expressing gRNA targeting LacZ vs expressing gRNA targeting ERCC6L2 after etoposide treatment (mean of n = 5 biological replicates ± SD). WT, wild-type. b Quantification of RPA32 positive RPE1 TP53^−/− cells by cell cycle status. Cells were treated for 30 min with 10 nM ATMi (AZD0156), then cells were treated with 100 µM of etoposide + 10 nM ATMi for 1 h (mean of n = 3 biological replicates ± SD). c Scheme for a genome-wide CRISPR knockout screen in RPE1 TP53^−/− (IC₂₀ = 120 nM, published in ref. ⁴¹) and TP53^−/−; ERCC6L2^−/− backgrounds (IC₂₀ = 45 nM). d Rank plots from normZ effect scores of etoposide vs DMSO of CRISPR knockout screens. e Clonogenic survival assay in RPE1 TP53^−/− titrated with etoposide (mean of n = 3 biological replicates ± SD). f Clonogenic survival assay in RPE1 TP53^−/− cells transfected with the indicated siRNAs and titrated with etoposide (mean of n = 3 biological replicates ± SD). g Quantification of RPA32 foci in RPE1 TP53^−/− cells treated with etoposide. Nuclei showing more than 5 RPA foci were selected (mean of n = 3 biological replicates). h Quantification of long-read sequencing reads with deletion lengths greater than 1 kb in RPE1 TP53^−/− cells treated with either DMSO or MRE11 inhibitor (MRE11i) (n = 1 biological replicate). i Quantification of PLA signal intensity for NBS1-ɣH2AX in RPE1 TP53^−/− cells treated with etoposide (mean of n = 3 biological replicates). j Quantification of PLA foci for MRE11-CtIP in etoposide-treated RPE1 TP53^−/− cells (mean of n = 2 technical replicates). k MRE11 peak profile surrounding each Cas12a gMulti target site in RPE1 TP53^−/− cells. l Normalized quantification of the area under the curve (AUC) of MRE11 at each of the 27 Cas12a gMulti target sites (1 biological replicate; mean ± SD). Statistical significance was determined by two-way ANOVA and Tukey’s multiple comparison test in (a, b, e, f); one-way ANOVA and Tukey’s multiple comparison test in (g); two-tailed Welch’s t-test in (l). Source data are provided as a Source Data file.