FIGURE 6.
Phosphorylation of eIF2α provides for resistance to UV irradiation. A, WT and eIF2α-S51A (A/A) MEF cells were treated with 40 J/m2 UV-C irradiation and cultured for 12 or 24 h. The number of viable cells was then determined by the MTT assay. B, the percentage of surviving cells after exposure to 40 J/m2 UV-C was determined by the clonogenic survival assay. NT indicates cells not treated with UV stress. The results in panels A and B correspond to the mean ± S.D. derived from three independent experiments and are normalized to the no treatment control. C, cells were subjected to the UV stress, cultured for up to 12 h as indicated, and phosphorylated eIF2α, β-actin, and apoptotic markers; cleaved caspase 3 and PARP were measured by immunoblot. 0 represents lysates not subjected to the UV stress.