A DNA ligase, most likely LIG1 (DNA ligase I), ligates single strand breaks (SSBs) remaining after RAD52-mediated single strand annealing (SSA) of resected DNA double-strand breaks (DSBs) and cleavage of displaced flaps by ERCC1:XPF (ERCC1:ERCC4). LIG4 is not involved in SSA (Maruta et al. 2024), and the activity of LIG3 is inhibited in the presence of RAD51 (Batenburg et al. 2023). Therefore, the only remaining candidate DNA ligase is LIG1. While LIG1 does not require RPA to bind to single-strand breaks in DNA, the RPA complex, which coats long resected ends created during SSA and homologous recombination repair (HRR), greatly stimulates the catalytic activity of LIG1 (Ranalli et al. 2002).