Aged hematopoietic stem cells (HSCs) exhibit compromised reconstitution capacity and differentiation bias toward myeloid lineages. However, the molecular mechanism behind HSC aging remains largely unknown. In this study, we observed that RNA N¹-methyladenosine-generating methyltransferase TRMT6–TRMT61A complex is increased in aged murine HSCs due to aging-declined CRL4^DCAF1-mediated ubiquitination degradation signaling. Unexpectedly, no difference of tRNA N¹-methyladenosine methylome is observed between young and aged hematopoietic stem and progenitor cells, suggesting a noncanonical role of the TRMT6–TRMT61A complex in the HSC aging process. Further investigation revealed that enforced TRMT6–TRMT61A impairs HSCs through 3′-tiRNA-Leu-CAG and subsequent RIPK1–RIPK3–MLKL-mediated necroptosis cascade. Deficiency of necroptosis ameliorates the self-renewal capacity of HSCs and counters the physiologically deleterious effect of enforced TRMT6–TRMT61A on HSCs. Together, our work uncovers a nonclassical role for the TRMT6–TRMT61A complex in HSC aging and highlights a therapeutic target.

衰老的造血干细胞（HSC）表现出受损的重建能力和向骨髓谱系的分化倾向。然而，HSC 衰老背后的分子机制仍然很大程度上未知。在这项研究中，我们观察到，由于衰老下降的 CRL4 ^DCAF1介导的泛素化降解信号，老年小鼠 HSC 中 RNA N ^{1 -}甲基腺苷生成甲基转移酶 TRMT6-TRMT61A 复合物增加。出乎意料的是，在年轻和老年造血干细胞和祖细胞之间没有观察到tRNA N ^{1 -}甲基腺苷甲基化组的差异，这表明TRMT6-TRMT61A复合物在HSC衰老过程中具有非典型作用。进一步的研究表明，强制 TRMT6-TRMT61A 通过 3'-tiRNA-Leu-CAG 和随后的 RIPK1-RIPK3-MLKL 介导的坏死性凋亡级联损害 HSC。坏死性凋亡的缺陷改善了 HSC 的自我更新能力，并抵消了强制 TRMT6-TRMT61A 对 HSC 的生理有害影响。我们的工作共同揭示了 TRMT6-TRMT61A 复合物在 HSC 衰老中的非经典作用，并强调了治疗靶点。