Apoptosis-inducing protein that modulates the tumor suppressor function of CDKN2A/p14ARF. Enhances the stability of CDKN2A/p14ARF protein by protecting it from degradation. May act as a tumor suppressor (PubMed:22094112). Colocalizes with CDKN2A/p14ARF in the nucleolus. Widely expressed. Up-regulated after serum withdrawal.