Component of the mitochondrial ribosome large subunit (PubMed:25278503, PubMed:25838379, PubMed:28892042). Also involved in apoptosis and cell cycle (PubMed:16024796, PubMed:16256947). Enhances p53/TP53 stability, thereby contributing to p53/TP53-induced apoptosis in response to growth-inhibitory condition. Enhances p53/TP53 translocation to the mitochondria. Has the ability to arrest the cell cycle at the G1 phase, possibly by stabilizing the CDKN1A and CDKN1B (p27Kip1) proteins (PubMed:16024796).