(H) Reconstitution of SOX9 ubiquitylation reaction by FLAG-FBW7α in vitro. Immobilized-IVT HA-SOX9 WT were incubated with complete ubiquitylation reaction mixture containing either the eluted FLAG-FBW7α-WT or the ΔF mutant for 60 minutes at 37◦C. Reaction mixture lacking the UbE1, an E1 ubiquitin-activating enzyme, or UbcH3, an E2 ubiquiting-conjugating enzyme, served as negative control for the reaction. SOX9 ubiquitylation was assessed following elution of the protein from the immobilized beads under denaturing condition as described in Materials Methods. The set of blots shown is representative from 3 independent experiments. 