Efficient repair of PARPi-induced DSBs in S-phase human cells depends on HDR pathways, which require the DNA damage response proteins BRCA1/2 (Zhang et al., 1998; Venkitaraman, 1999), ATM/ATR (Paulovich and Hartwell, 1995), Chk1/2 (Paulovich and Hartwell, 1995; Sanchez et al., 1996; Matsuoka et al., 1998), PALB2 (Xia et al., 2006; Rahman et al., 2007), and BRIP1 (Bridge et al., 2005); the Fanconi Anemia (FA) proteins; and the HDR proteins that include EXO1 (Mimitou and Symington, 2008; Zhu et al., 2008), DNA2 (Zhu et al., 2008; Cejka et al., 2010), and RAD51 (Davies et al., 2001). This evidence concerns the gene BRCA1 and Friedreich ataxia.