Cyclin-dependent kinase inhibitor 2A (P14ARF) is capable of inducing cell cycle arrest in G1 and G2 phases. P14ARF acts as a tumor suppressor. P14ARF binds to MDM2 and blocks its nucleocytoplasmic shuttling by sequestering it in the nucleolus. This inhibits the oncogenic action of MDM2 by blocking MDM2-induced degradation of p53 and enhancing p53-dependent transactivation and apoptosis. P14ARF also induces G2 arrest and apoptosis in a p53-independent manner by preventing the activation of cyclin B1/CDC2 complexes.