Figure 2. Ionizing radiation induces polyubiquitination-mediated proteasomal degradation of TTP.

(A) U2OS cells overexpressing human TTP were sham irradiated or exposed to 4 Gy and were either left untreated for the next 24 h or treated with 2 μM MG132 for the last 4 h. Cell lysates were subjected to immunoprecipitation using TTP antibody followed by immunoblotting using ubiquitin (Ub) antibody. (B) MH-S (left panel) and MRC-5 (right panel) cells were irradiated as above. Cells were then either left untreated or 6 h after irradiation treated with 2 μM MG132 for the next 4 hours. Cell lysates were then subjected to immunoprecipitation and immunoblotting using indicated antibodies.