Regulator that plays a central role in regulation of apoptosis via its interaction with p53/TP53 (PubMed:11684014, PubMed:12524540). Regulates TP53 by enhancing the DNA binding and transactivation function of TP53 on the promoters of proapoptotic genes in vivo. . This is the function of Ensembl gene identifier ENSG00000088808 (PPP1R13B, protein phosphatase 1 regulatory subunit 13B).