Measurement of BIR efficiency in cells carrying an empty vector or expressing DPB11BRCT3/4 fused to wild-type or mutant versions of SGS1. Mutants include a helicase deficient allele of SGS1 (SGS1hd) or an allele lacking the Top3 Interacting Motif (TIM; SGS1TIM). Error bars represent SEM of at least 3 replicate experiments. P value was calculated with a two-tailed, unpaired t-test. * = p≤0.05; ** = p≤0.01; *** = p ≤0.001. C. Measurement of BIR efficiency in cells carrying an empty vector or expressing DPB11BRCT3/4 fused to either SGS1, TOP3, or RMI1. Error bars represent SEM of at least 3 replicate experiments. P value was calculated with a two-tailed, unpaired t-test. * = p≤0.05; ** = p≤0.01; *** = p ≤0.001. D. Measurement of BIR efficiency in cells carrying an empty vector or DPB11BRCT3/4 fused to either SGS1, hBLM, PIF1, or RRM3. Error bars represent SEM of at least 3 replicate experiments. P value was calculated with a two-tailed, unpaired t-test. * = p≤0.05; ** = p≤0.01; *** = p ≤0.001. 