Figure 2.

Composition of the E3 complexes targeting Snail1 and Snail2. The Skp-1-Cullin-1-F-Box (SCF) E3s, SCF-Fbxl14 and SCF-Fbxl5 are multimeric E3 ligases that mediates the ubiquitin (Ub) transfer from the E2 conjugating enzyme to Snail. SCF E3s are composed of the scaffold protein Cullin1 (Cul1), which interacts with Skp1 and the RING-finger protein Rbx1. The substrate binding affinity is mediated by the F-box protein (β-TrCP1, Fbxl14 and Fbxl5). The SCF-β-TrCP1 binds Snail1 only when double-phosphorylated by GSK-3β. Mdm2 is a single-subunit RING-finger E3 that targets Snail2 when p53 is bound.