FIGURE 2.

Both PERK and GCN2 contribute to UVB-induced phosphorylation of eIF2α. HaCaT cells were transiently transfected with either PERK or GCN2 siRNA (10 nm). A scrambled siRNA (10 nm) was also transfected into HaCaT cells as control. A, the transfected cells were metabolically labeled with [³⁵S]Met/Cys and immunoprecipitated using anti-PERK or anti-GCN2 antibodies. The immunoprecipitates were resolved on SDS-PAGE. The newly synthesized PERK and GCN2 were visualized by autoradiograph. B, the transfected cells were treated or not treated with UVB (50 mJ/cm²). The amounts of total eIF2α, phosphorylated eIF2α, and β-actin were measured by Western blot analysis. The levels of phosphorylated eIF2α were normalized by the levels of β-actin and expressed as a percentage of phosphorylated eIF2α.