Our findings suggest a fundamental mechanistic difference in “synthetic lethality” between FA cells and cells deficient in other genes involved in the HR repair pathway, such as BRCA1-, BRCA2-, and ATM30, 31, 32, 33, 34, whose hypersensitivity to PARP inhibition is totally dependent on suppression of NHEJ by PARP1. The gene discussed is BRCA1; the disease is Friedreich ataxia.