Inhibition of Ribosome Biogenesis in vivo Causes p53-Dependent Death and p53-Independent Dysfunction

Ribosomes are critical for cell function; their synthesis (known as ribosome biogenesis; "RiBi") is complex and energy-intensive. Surprisingly little is known about RiBi in differentiated cells in vivo in adult tissue. Here, we generated mice with conditional deletion of Nat10, an essential gene for RiBi and translation, to investigate effects of RiBi blockade in vivo. We focused on RiBi in a long-lived, ribosome-rich cell population, pancreatic acinar cells, during homeostasis and tumorigenesis. We observed a surprising latency of several weeks between Nat10 deletion and onset of structural and functional abnormalities and p53-dependent acinar cell death, which was associated with translocation of ribosomal proteins RPL5 and RPL11 into acinar cell nucleoplasm. Indeed, deletion of Trp53 could rescue acinar cells from apoptotic cell death; however, Nat10{Delta}/{Delta}; Trp53{Delta}/{Delta} acinar cells remained morphologically and functionally abnormal. Moreover, the deletion of Trp53 did not rescue the lethality of inducible, globally deleted Nat10 in adult mice nor did it rescue embryonic lethality of global Nat10 deletion, emphasizing p53-independent consequences of RiBi inhibition. Deletion of Nat10 in acinar cells blocked Kras-oncogene-driven pancreatic intraepithelial neoplasia and subsequent pancreatic ductal adenocarcinoma, regardless of Trp53 mutation status. Together, our results provide initial insights into how cells respond to defects in RiBi and translation in vivo.