Posttranscriptional modifications in transfer RNA (tRNA) are often critical for normal development because they adapt protein synthesis rates to a dynamically changing microenvironment. However, the precise cellular mechanisms linking the extrinsic stimulus to the intrinsic
RNA modification pathways remain largely unclear. Here, we identified the cytosine-5 RNA
methyltransferase NSUN2 as a sensor for external stress stimuli. Exposure to oxidative
stress efficiently repressed NSUN2, causing a reduction of methylation at specific tRNA
sites. Using metabolic profiling, we showed that loss of tRNA methylation captured cells in a
distinct catabolic state. Mechanistically, loss of NSUN2 altered the biogenesis of tRNAderived noncoding fragments (tRFs) in response to stress, leading to impaired regulation of
protein synthesis. The intracellular accumulation of a specific subset of tRFs correlated with
the dynamic repression of global protein synthesis. Finally, NSUN2-driven RNA methylation
was functionally required to adapt cell cycle progression to the early stress response. In
summary, we revealed that changes in tRNA methylation profiles were sufficient to specify
cellular metabolic states and efficiently adapt protein synthesis rates to cell stress.