Fig. 4.

SOCS1 counter-regulates reactive oxygen species (ROS) responsible for the survival signal during radiation response to promote apoptosis. HCT116/p53 wt cells were irradiated with γ-IR at 5 Gy with or without NAC treatment (1 h pretreatment at 1 mM). Cells were analyzed for signaling mediators by immunoblotting (A) and ROS generation (B) at 30 min. Cell death was measured at 24 h post irradiation by propidium iodide and Annexin-V staining (C). The γ-IR-induced ROS generation was assessed in cells with SOCS1 knock-down at 10 min and with SOCS1 over-expression at indicated time points (D, E). HCT116/p53 wt cells transfected with Flag or Flag-Trx1 were irradiated at 5 Gy and analyzed for ROS generation, apoptotic response and Trx1 expression at 24 h (F, G).