Degradation of p27fs177 occurs through Skp2-dependent pathways. (a) Expression of p27 and α-tubulin (control) were assessed in siRNA-treated and untreated cells. (b) Validation of efficient knockdown of Skp2 using different DNA concentrations. Probing the membrane with α-tubulin ensured equal protein loading. (c) To verify the specificity of the siRNA-mediated knock-down of Skp2, a scrambled siRNA oligo was transfected in parallel with p27wt plasmid. siRNA for knock-down of KPC1 was included as positive control as this protein also degrades p27wt. Probing the membrane with α-tubulin ensured equal protein loading. (d) A ubiquitin mutant (pUbr7) co-transfected in parallel with the p27wt and p27fs177 expression vectors has no effect on p27fs177 degradation.