This peptide, amino acids 140 to 147 fragment of p21, is phosphorylated on Thr145. Pim-1 can efficiently phosphorylate p21 on Thr145 in vitro. Pim-1 is a serine/threonine kinase involved in the transduction of cytokine-triggered mitogenic signals. When p21 is phosphorylated on Thr145, it localizes to the nucleus and causes the disruption of the association between proliferating cell nuclear antigen and p21. Phosphorylation of Thr145 promotes stabilization of p21.