SLFN11-mediated tRNA regulation induces cell death by disrupting proteostasis in response to DNA-damaging agents

DNA-damaging agents (DDAs) have long been used in cancer therapy. However, the precise mechanisms by which DDAs induce cell death are not fully understood and drug resistance remains a major clinical challenge. Schlafen 11 (SLFN11) was identified as the gene most strongly correlated with the sensitivity to DDAs based on mRNA expression levels. SLFN11 sensitizes cancer cells to DDAs by cleaving and downregulating tRNA ^Leu (TAA). Elucidating the detailed mechanism by which SLFN11 induces cell death is expected to provide insights into overcoming drug resistance. Here, we show that, upon administration of DDAs, SLFN11 cleaves tRNA ^Leu (TAA), leading to ER stress and subsequent cell death regulated by inositol-requiring enzyme 1 alpha (IRE1α). These responses were significantly alleviated by SLFN11 knockout or transfection of tRNA ^Leu (TAA). Our proteomic analysis suggests that tRNA ^Leu (TAA) influences proteins essential for maintaining proteostasis, especially those involved in ubiquitin-dependent proteolysis. Additionally, we identified the cleavage sites of tRNA ^Leu (TAA) generated by SLFN11 in cells, and revealed that tRNA fragments contribute to ER stress and cell death. These findings suggest that SLFN11 plays a crucial role in proteostasis by regulating tRNAs, and thus determines cell fate under DDA treatment. Consequently, targeting SLFN11-mediated tRNA regulation could offer a novel approach to improve cancer therapy.