FIGURE 7.

Degradation of PCNA is proteosome-dependent. A and B, A549 cells were UV-irradiated at 46 J/m² and then incubated for 24 h with DMSO or MG132 at 25 μm, or NS-siRNA or MTH2-siRNA was transfected into A549 cells for 48 h with DMSO or MG132 at 25 μm. Proteins were extracted for Western blotting with anti-PCNA. The lower column diagram represents the average band intensity of PCNA with standard error from several independent experiments. C, A549 cells were treated with UV (46 J/m², 24 h) or MTH2-siRNA in the presence of proteasome inhibitors (25 μm MG132). The treated cells were then lysed and immunoprecipitated with anti-PCNA, followed by Western blotting with anti-ubiquitin.