Model of p21 translational regulation.

<p>Upon amino acid deprivation, GCN2 phosphorylates eIF2α, which delays translation initiation. This results in ribosomes bypassing 5’ uORFs in the p21 variant 2 transcript and beginning translation at the p21 ORF, resulting in p21 upregulation under stress. This pathway is distinct from p53-dependent transcriptional upregulation of p21. Induction of p21 upon nutrient deprivation leads to G_<b>1</b>/S arrest and promotes cell survival.