Fig. 5

Breast cancer susceptibility protein-1 (BRCA1)-deficient breast cancer cells depleted of both EEPD1 and RAD52 rely on alternative non-homologous end-joining pathway (aNHEJ) for survival. MDA-MB-436 BRCA1^-/- cells were transfected with control, endonuclease/exonuclease/phosphatase family domain-containing-1 (EEPD1)/radiation repair protein 52 (RAD52) with or without X-ray repair cross-complementing protein (XRCC4), DNA ligase IV (LIG4) or polymerase theta (POLQ) siRNA for 48 h and cells were plated for colony formation survival assays. a Western blot analysis of EEPD1, RAD52, XRCC4, LIG4, and POLQ protein expression with cyclophilin B (CypB) as a loading control in the transfected BRCA1^-/- cancer cells. b Representative images of clonal colonies from each condition after 14 days. c Quantitative analysis of colony formation that targeted the classical non-homologous end-joining (cNHEJ) pathway or aNHEJ pathway. Each experiment was performed more than three distinct times in triplicate (*p < 0.05, **p < 0.01, ***p < 0.001)