FIG 5.

PA28γ attenuates SCF^Fbl12-induced p21 ubiquitination. (A) HEK 293, HeLa, and HCT116 cells were transfected with either Myc-PA28γ or control vector. Cell lysates were subjected to immunoblot analysis. (B) HEK 293 cells were transfected with either control or Myc-Fbl12 plasmids. Cellular proliferation was analyzed using the Cell Counting Kit-8 (n = 3; means ± SEM; *, P < 0.05 by Student's t test). (C) Ubiquitinated proteins were purified from denatured cell lysates using Talon metal affinity resin and analyzed by immunoblotting. Expression of PA28γ reduced SCF^Fbl12-induced p21 ubiquitination. (D) Coimmunoprecipitation of Flag-Fbl12, p21, and Myc-PA28γ in HEK 293T cells. Ectopic expression of Fbl12 promoted the association of p21 with PA28γ.