MYC Drives mRNA Pseudouridylation to Mitigate Proliferation-Induced Cellular Stress during Cancer Development.

Pseudouridylation is a common RNA modification that is catalyzed by the family of pseudouridine synthases (PUS). Pseudouridylation can increase RNA stability and rigidity, thereby impacting RNA splicing, processing, and translation. Given that RNA metabolism is frequently altered in cancer, pseudouridylation may be a functionally important process in tumor biology. Here, we showed that the MYC family of oncoproteins transcriptionally upregulates PUS7 expression during cancer development. PUS7 was essential for the growth and survival of MYC-driven cancer cells and xenografts by promoting adaptive stress responses and amino acid biosynthesis and import. ATF4, a master regulator of stress responses and cellular metabolism, was identified as a key downstream mediator of PUS7 functional activity. Induction of ATF4 by MYC oncoproteins and cellular stress required PUS7, and ATF4 overexpression overcame the growth inhibition caused by PUS7 deficiency. Mechanistically, PUS7 induced pseudouridylation of MCTS1 mRNA, which enhanced its translation. MCTS1, a noncanonical translation initiation factor, drove stress-induced ATF4 protein expression. A PUS7 consensus pseudouridylation site in the 3' untranslated region of ATF4 mRNA was crucial for the induction of ATF4 by cellular stress. These findings unveil a MYC-activated mRNA pseudouridylation program that mitigates cellular stress induced by MYC stimulation of proliferation and biomass production, suggesting that targeting PUS7 could be therapeutic strategy selectively against MYC-driven cancers.