Trib1 and Trib2, but not Trib3, induce efficient degradation of C/EBPα. (A) Western blot for C/EBPα in sorted 32D cells transduced with MigR1, Trib1, Trib2, or Trib3 and treated with either the proteasome inhibitor MG132 or the DMSO control. Endogenous C/EBPα expression was determined with an anti-C/EBPα antibody. β-Actin served as the protein loading control. Data are representative of 3 independent experiments. (B) Western blot for endogenous ACC in HeLa cells transfected with Trib3 and the E3 ubiquitin ligase COP1. (C) Western blot for endogenous ACC in HeLa cells transfected with the indicated Tribbles constructs and COP1. In panels B and C, ACC was detected with an anti-ACC antibody, COP1 was detected with an anti-HA antibody, Tribs were detected with an anti-FLAG antibody, and β-actin was the protein loading control. Data are representative of 2 independent experiments.