mTOR takes charge: Relaying uncharged tRNA levels by mTOR ubiquitination.

Nutrient availability is conveyed to the mechanistic target of rapamycin (mTOR), which couples metabolic processes with cell growth and proliferation. How mTOR itself is modulated by amino acid levels remains poorly understood. Ge and colleagues now demonstrate that broad sensing of uncharged tRNAs by GCN2/FBXO22 inactivates mTOR complex 1 (mTORC1) via mTOR ubiquitination.