Pseudouridylation of tRNA-derived fragments steers translation control in stem cells [Polysome-Seq]

Pseudouridylation (pseudouridine) is the most abundant and widespread type of RNA epigenetic modification in living organisms; however, the biological role of pseudouridine remains poorly understood. Here, we show that a pseudouridine-driven posttranscriptional program steers translation control to impact stem cell commitment during early embryogenesis. Mechanistically, the pseudouridine ‘writer’ PUS7 modifies and activates a network of tRNA-derived fragments (tRFs) targeting the translation initiation complex. PUS7 inactivation in embryonic stem cells impairs tRF-mediated translational regulation leading to high protein biosynthesis and abnormal germ layer specification. Dysregulation of PUS7 and tRFs in myeloid malignancies associates with altered translation rates, suggesting a role of pseudouridine in tumorigenesis. Our findings unveil a critical function of pseudouridine in directing translational control in stem cells with promisingly broad implications for human disease.