EXO1 and invasive breast carcinoma: Moreover, high levels of RNA polymerase θ (Pol θ), a protein important for DSB repair by alternative end-joining (altEJ), are associated with poor outcome in breast, ovarian, and other tumors, and recent analysis demonstrates that EXO1 and BLM1 cocluster with Pol θ within a cohort of genes strongly correlated with poor outcome in invasive breast carcinomas (Wood and Doublie 2016).