GCN2 activation and eIF2alpha phosphorylation in the maturation of mouse oocytes.

GCN2 is one of the four mammalian kinases that phosphorylate the alpha subunit of the translation initiation factor 2 (eIF2alpha) in a variety of stress situations, resulting in protein synthesis inhibition. GCN2 is involved in regulating metabolism, feeding behavior and memory in rodents. We show here that, relative to other cells, the beta isoform of the GCN2 transcript and the GCN2 protein are highly abundant in unfertilized mouse eggs. In addition, GCN2 in these cells is active, resulting in elevated levels of phosphorylated eIF2alpha. After fertilization, eIF2alpha phosphorylation decreases drastically. These results suggest that GCN2 mediated translational control may contribute to regulatory mechanisms operating during oocyte maturation.