Fig 1: (A) TIF-IA silencing by shRNA led to increased and prolonged p53 levels after UVC-irradiation. Stable transfected HCT116 cells have been irradiated with 10J/m2 UVC and analysed for p53 stabilisation by western blot. (B) P53 levels in whole cell lysates of HCT116 cells treated with the specific Pol I inhibitor CX-5461 and irradiated with 10J/m2 UVC. (C, D) CoIP experiments of HCT116 cells treated with either CX-5461 or UVC-irradiation or a combination of both. Cells were first incubated with 5µM of MG132 for 12h. Afterwards one group was treated with 150nM CX-5461, a second group was irradiated with 10J/m2 UVC and the third group was treated with 150nM CX-5461 as well as irradiated with 10J/m2 UVC. Whole cell lysates were prepared 24h after UVC-irradiation and subsequently used for CoIP. Precipitated and co-precipitated proteins were analysed on western blots. (C) IP of p53 and CoIP of HDM2. (D) IP of HDM2 and CoIP of ribosomal protein L11 (rp L11). Blots are representatives of at least three independent experiments.