Figure 5.

Dioscin promoted the ubiquitination of c-myc. (A) Proteasome inhibitor MG132 antagonized dioscin-mediated c-myc reduction. CRC cell was pretreated with 20 μM MG132 and then treated with 5μM dioscin; the expression of c-myc was examined by Western blotting. (B) Dioscin increases the ubiquitination levels of c-myc. HCT-116 cells were pretreated with 20 μM MG132 and then incubated with indicated dioscin, the cell lysates were immunoprecipitated with anti-c-myc antibody and then probed with anti-ubiquitin antibody. (C) FBW-7 was involved in dioscin-mediated ubiquitination of c-myc. HCT-116 were transfected with FBW7 siRNA and then treated with 5μM dioscin, the ubiquitination of c-myc was detected as described. (D) Dioscin enhanced the binding between c-myc and FBW-7. HCT-116 cells were treated with 5μM dioscin, the cell lysates were immunoprecipitated with anti-FBW7 antibody, and the precipitation was probed with the anti-c-Myc antibody.