Exonuclease Xrn1 regulates TORC1 signaling in response to SAM availability

Autophagy is a conserved process of cellular self-digestion that promotes survival during nutrient stress. In yeast, methionine starvation is sufficient to induce autophagy. One pathway of autophagy induction is governed by the SEACIT complex, which regulates TORC1 activity in response to amino acids through the Rag GTPases Gtr1 and Gtr2 This work identifies an unexpected yet critical role for Xrn1 in nutrient sensing and growth control that extends beyond its canonical housekeeping function in RNA degradation and indicates an avenue for RNA metabolism to function in amino acid signaling into TORC1.细胞自噬（Autophagy）是一类保守的细胞自我吞噬过程，可在营养胁迫条件下促进细胞存活。在酵母中，甲硫氨酸饥饿足以诱导细胞自噬。一条细胞自噬诱导通路由SEACIT复合物（SEACIT complex）调控，该复合物通过Rag GTP酶（Rag GTPases）Gtr1与Gtr2响应氨基酸水平，以调控雷帕霉素靶蛋白复合物1（TORC1）的活性。本研究揭示了Xrn1在营养感知与生长调控中此前未被发现的关键作用，该功能超越了其在RNA降解中的经典持家功能，同时指出RNA代谢可通过参与向TORC1传递的氨基酸信号通路发挥功能的新方向。