| RPL11 is a basic ribosomal protein of the L5P family that forms part of the 60S large ribosomal subunit, where it associates with 5S rRNA within the 5S ribonucleoprotein particle and contributes to large subunit assembly, rRNA maturation, and the structural integrity required for peptidyl transferase activity during translation. The protein adopts an RNA‑binding fold that enables high‑affinity interaction with 5S rRNA and integration into the 5S RNP, and this preassembled 5S RNP containing RPL11, RPL5, and 5S rRNA is incorporated into pre‑60S particles in the nucleus, a step that is essential for proper large subunit formation and export. Beyond its structural role in the ribosome, RPL11 functions as a central sensor in the “ribosomal stress” or “nucleolar stress” pathway; when large subunit biogenesis is perturbed, the 5S RNP accumulates in the nucleoplasm, where RPL11 directly binds the E3 ubiquitin ligase MDM2 and inhibits its activity toward p53, leading to stabilization and activation of p53 and induction of downstream cell‑cycle arrest and apoptosis programs. This interaction requires specific basic residues on RPL11 that engage MDM2, and the RPL11–MDM2–p53 axis couples defects in ribosome production to a transcriptional stress response, coordinating cell proliferation with ribosome assembly capacity. RPL11 also influences nucleolar architecture and PML localization, consistent with a broader role of the 5S RNP in organizing nucleolar and nucleoplasmic structures under conditions of disturbed ribosome biogenesis. Germline loss‑of‑function variants in RPL11 cause a subset of Diamond–Blackfan anemia, where reduced RPL11 levels impair 60S subunit production and 5S RNP formation, leading to defective erythroid differentiation and anemia, likely through combined effects on translational capacity and heightened p53 activation in hematopoietic progenitors. Somatic alterations or dysregulated expression of RPL11 and other 5S RNP components have been reported in cancer, where attenuation of the RPL11–MDM2 checkpoint can weaken p53 activation in response to ribosomal stress, whereas heightened RPL11 activity can enhance p53 responses to drugs that target ribosome biogenesis. |
