Fig. 4

Cyclin G2 inhibits Wnt/β-catenin signaling by promoting β-catenin degradation in a GSK-3β dependent manner. a β-catenin transcriptional activity of SGC-7901 and MGC-803 cells overexpressing cyclin G2 or control vector (NC) was determined by a TOPFlash luciferase reporter assay (n = 3). *P < 0.05. b Western blot analysis for the β-catenin expression in ectopic cyclin G2 overexpression in SGC-7901 or MGC-803 cells compared with the negative vector control. c TOPFlash luciferase reporter assays showed that ectopic cyclin G2 suppressed β-catenin transcriptional activity in HeLa, HT-29, HEK-293, and COS-7 cells. d COS-7 cells infected with incremental concentrations of recombinant retroviruses encoding CCNG2 (Re-cyclin G2) or a negative control gene were used for western blotting after 48 h incubation. Western blot analysis showed the overexpression of cyclin G2 inhibited β-catenin and c-Myc expression in a dose-dependent manner. e β-catenin and c-Myc expression levels in Ccng2^−/− and WT MEFs were analyzed by western blot. f Western blot analysis revealed that the expression and phosphorylation of β-catenin and GSK-3β in the negative control and cyclin G2-overexpressing COS-7 cells. g Western blot analysis for β-catenin protein levels in the control or cyclin G2-overexpressing COS-7 cells treated with or without GSK-3β inhibitor, LiCl (20 mM), for 24 h. NaCl was used as a negative control. h Western blot analysis to determine the β-catenin protein levels in the control or cyclin G2-overexpressing COS-7 cells treated with or without proteasome inhibitor, MG132 (25 μM), for 6 h. DMSO was used as a negative control