Figure 1. Phosphorylation of eIF2α by GCN2 is enhanced in response to UV irradiation.

GCN2^+/+ and GCN2^−/− MEF cells were subjected to increasing dosages of UV-C (A) or UV-B irradiation (B). After UV treatment, cells were incubated in the culture medium for 3 h and the levels of phosphorylation of eIF2α were measured by immunoblot by using a polyclonal antibody specific to eIF2α phosphorylated at Ser⁵¹. Equal amounts of proteins were analysed in each lane. Levels of total eIF2α were assayed by using an antibody that recognizes both phosphorylated and non-phosphorylated versions of the translation initiation factor. GCN2^+/+ and GCN2^−/− (C) or PEK^+/+ and PEK^−/− (E) MEF cells were subjected to 30 J/m² UV-C irradiation, incubated in the culture medium for between 0.25 and 8 h as indicated, and eIF2α phosphorylation was measured by immunoblot. (D) PEK^+/+ and PEK^−/− MEF cells were subjected to increasing dosages of UV-C, cultured for 3 h, and the amounts of eIF2α phosphorylation were measured by immunoblot. (F) S/S and A/A MEF cells were exposed to 30 J/m² UV-C irradiation, and after between 0.5 and 6 h incubation as indicated, phosphorylated eIF2α and total eIF2α levels were measured by immunoblot. Immunoblots in each panel are representative of three independent experiments.