Regulation of the MDM2-P53 pathway and tumor growth by PICT1 via nucleolar RPL11

This report identifies PICT1 as a new regulator of p53. PICT1 binds the ribosomal protein RPL11 and prevents its release from the nucleolus, precluding RPL11 from inhibiting MDM2 activity. Loss of PICT1 increases p53 abundance and protects from tumorigenesis in mice. PICT1 is also a prognostic marker in human cancers. This p53-dependent protumorigenic function is in contrast with previous reports suggesting a tumor-suppressor role for PICT1.