HEK293T (ATCC CRL-3216), U2OS (ATCC HTB-96), U2OS-265 (34 (link)) and U2OS DR-GFP (ATCC CRL-3455) cells were grown in DMEM (ThermoFisher Scientific 10569044) supplemented with 10% FBS (R&D solutions S11150) at 37°C with 5% CO2. U2OS-265 DSB reporter cells were a generous gift from Roger Greenberg (34 (link)).