Dual regulation of p53 by the ribosome maturation factor SBDS

The Shwachman-Bodian Diamond syndrome (SBDS)-associated gene, SBDS, is involved in rRNA synthesis and ribosome maturation, but the role of SBDS in cancer is largely elusive. In this study, we found that SBDS is often overexpressed or amplified in human cancers, and high level of endogenous SBDS is significantly associated with unfavorable prognosis. Conversely, knockdown of SBDS leads to p53 stabilization and activation through the ribosomal stress-RPL5/RPL11-MDM2 pathway, resulting in the repression of cancer cell proliferation and invasion. Interestingly, ectopic SBDS in the nucleoplasm also suppresses tumor cell growth and proliferation in vitro and in vivo. Mechanistically, ectopically expressed SBDS triggered by, for example, ribosomal stress binds to the transactivation domain of p53 and perturbs the MDM2–p53 interaction, consequently leading to impaired p53 ubiquitination and proteasomal degradation. Altogether, our finding for the first time demonstrates the dual functions of SBDS in cancer development by coordinating ribosome biogenesis and p53 activity.