The endogenous binding of these E2–E3 pairs was further confirmed in two lung cancer cell lines under physiological unstressed conditions in a pull-down assay using antibody against either SAG or RBX1 (Figs 4B and S4B) or antibodies against each of four E2s (Figs 4C and S4C). This evidence concerns the gene RBX1 and lung carcinoma.