The p53 tumor-suppressor gene integrates numerous signals that control cell life and death. Several novel molecules involved in p53 signaling, including p53R2, Chk2, p53AIP1, Noxa, PIDD, and PID/MTA2, were recently discovered. p53R2 is a p53 inducible gene that contains a p53 binding sequence and encodes a subunit of the enzyme ribonucleotide reductase. p53R2 is induced by the reagents, ultraviolet and -irradiation that cause DNA damages. The product of p53R2 gene is directly involved in the p53 checkpoint for repair of damaged DNA. The isoform of the p53 family member p73 also induces p53R2 expression. p53R2 is an important target of p53 for tumor suppression. Synonyms: Anti-Inducible Ribonucleotide Reductase Small Subunit 2-Like Protein.