(f) HeLa cells stably interfered for AMBRA1 were co-transfected with vectors encoding Ub-Lys-63-HA and AMBRA1WT or AMBRA1S52A, respectively. Protein extracts were immunoprecipitated using an anti-ULK1 antibody and ubiquitin Lys-63-HA, ULK1, AMBRA1 and actin were analysed by western blotting. 