To this end, we utilised U2OS (human osteosarcoma) cells, a model system widely used to study DDR mechanisms, specifically monoclonal U2OS cells, stably expressing doxycycline-inducible wildtype (wt) or catalytically dead GFP-UBE2D1 (active cysteine C85 mutated to serine; C85S) [12]. Here, UBE2D1 is linked to osteosarcoma.