Assays

HeLa cells stably expressing UBE2QL1-APEX2 were grown in lysine- and arginine-free DMEM supplemented with FBS, L-Glutamine, Sodium pyruvate, heavy arginine (R10) (38 μg/ml) and lysine (K8) (66 μg/ml) or light arginine (R0) (38 μg/ml) and lysine (K0) (66 μg/ml), respectively. Further experiments were conducted as soon as the cells reached a protein labelling with heavy amino acids of at least 95%. Heavy-labeled cells were treated with 250 μM Leu-Leu methyl ester hydrobromide (LLOMe, Sigma) for 3 ...