Abstract

In ribosomopathies, perturbed expression of ribosome components leads to tissue-specific phenotypes, such as limb and craniofacial defects as well as bone marrow failure. What accounts for such tissue-selective manifestations as a result of mutations in the ribosome, a ubiquitous cellular machine, has remained a mystery. Combining comprehensive mouse genetics and in vivo ribosome profiling, we observe limb patterning phenotypes in ribosomal protein (RP) haploinsufficient embryos and uncover corresponding selective translational changes of transcripts controlling limb development. Surprisingly, both loss of p53, which is activated by RP haploinsufficiency, and augmented protein synthesis rescue these phenotypes. These findings are reconciled by the unexpected identification that p53 functions as a master regulator of protein synthesis through transcriptional activation of 4E-BP1. 4E-BP1, a key regulator of translation, in turn, facilitates selective changes in the translatome downstream of p53 and thereby explains, at least in part, how RP haploinsufficiency elicits specificity to gene expression. These results provide an integrative model to explain how in vivo tissue-specific phenotypes emerge from a mutation in a ribosome component.