Figure 7. H₂O₂ induces C/EBPδ ubiquitination.

(a) Ubiquitination of C/EBPδ in HC11 cells in response to various stress conditions. HC11 cells were co-transfected with HA-Ub and C/EBPδ expression vectors, and then treated with 100 μM CoCl₂ (6 h), 1 mM H₂O₂ (2 h), 2 μM doxorubicin (6 h) or 5 mM MMS (2 h). Control (CON) cells were treated with water. The bottom panel shows the protein levels of transfected C/EBPδ constructs. (b) Ubiquitination of C/EBPδ in response to different H₂O₂ doses. The left panel shows ubiquitination of C/EBPδ. The bottom panel shows the protein levels of transfected C/EBPδ constructs. The right panel shows total ubiquitinated cellular proteins. (c) H₂O₂ treatment does not influence C/EBPδ protein stability. HC11 cells were pretreated with water (control) or 1 mM H₂O₂ for 2 h before addition of emetine, and then harvested at intervals of 2 h after addition of emetine. Protein contents were normalized to β-actin and plotted.