Fig. 2

FBXW7 mutants selectively target c-Myc, CyclinE and MCL1 for degradation. a GSK3 phosphates NOTCH1, cyclin E, MCL1 and c-MYC at specific phosphodegrons. The phosphorylation is essential for FBXW7-mediated proteasome degradation. Oncoprotein specific inhibitors are indicated the Figs. b FBXW7 mutations are correlated with poor prognosis in TCGA pan-cancer analysis. c FBXW7 W425R increased the half-life of cyclin E and c-MYC but had no effect on MCL1 half-life. The effect of FBXW7 on the half-life of oncoproteins was determined by Western blot after cells treated with 100 μg/mL cycloheximide (CHX) for 0, 2, 4, and 6 h. d FBXW7 mutations impaired the degradation of oncoproteins. FBXW7-mediated degradation of oncoproteins was determined by Western blot. FBXW7 WT and R505C were used as positive and negative controls, respectively. e The interaction between FBXW7 and oncoproteins was analyzed by co-immunoprecipitation. 293 T cells co-transfected with FBXW7 and oncoprotein were lysed and immunoprecipitated with oncoprotein. Western blot was used to analyze the interaction between FBXW7 and oncoproteins. f FBXW7-mediated ubiquitination of cyclin E and c-MYC was deficient by FBXW7 mutations. 293 T cells were co-transfected with indicated FBXW7, K48-Ub and cyclin E (upper panel) or c-MYC (lower panel). Cells were treated with MG132 for 6 h before harvest. Immunoprecipitated cyclin E or c-MYC and Western blot Ub showed the ubiquitination level of cyclin E (upper panel) and c-MYC (lower panel). g Table summarizing FBXW7 wild-type and FBXW7 mutants