USP5 abolishes c-Maf degradation induced by HERC4. (A) USP5 was identified in the c-Maf immunoprecipitates by liquid chromatography-MS/MS. Unique peptides in USP5 identified by MS were highlighted. (B) HEK293 cells were transfected with c-Maf, USP5, and Ub plasmids. Forty-eight hours later, cell lysates were prepared for IP with an anti-HA antibody, followed by IB assay against ubiquitin (anti-Flag). (C) HEK293 cells were cotransfected with c-Maf, HERC4, and USP5 alone or together. Forty-eight hours later, cell lysates were prepared for IB. (D) HEK293 cells were transfected with c-Maf, HERC4, with or without USP5 for 24 hours followed by CHX treatment for indicated duration. Cell lysates were then prepared for IB assay.