(C) Co-immunoprecipitation of HA-SOX9 with either wild type (WT) or R465A- FLAG-FBW7α. Unlike the wild type protein, FLAG-FBW7α containing arginine 465 mutation did not significantly co-immunoprecipitate with HA-SOX9 (IP with anti HA antibody) and vice versa (IP with anti FLAG antibody). The expressions of HA-SOX9 and FLAG- FBW7α- WT or R465A mutant were assessed in the whole cell extract (WCE) of the transfected HEK293 with GAPDH protein used to indicate total protein loading. 