Velcrin-induced selective cleavage of tRNALeu(TAA) by SLFN12 causes cancer cell death [RNA-Seq]

Velcrin compounds kill cancer cells expressing high levels of phosphodiesterase 3A (PDE3A) and Schlafen family member 12 (SLFN12) by inducing complex formation between these two proteins, but the mechanism of cancer cell killing by the PDE3A–SLFN12 complex is not fully understood. Here, we report that the physiological substrate of SLFN12 RNase is tRNALeu(TAA). SLFN12 selectively digests tRNALeu(TAA), and velcrin treatment promotes the cleavage of tRNALeu(TAA) by inducing PDE3A–SLFN12 complex formation in vitro. We found that distinct sequences in the variable loop and acceptor stem of tRNALeu(TAA) are required for substrate digestion. Velcrin treatment of sensitive cells results in downregulation of tRNALeu(TAA), ribosome pausing at Leu-TTA codons and global inhibition of protein synthesis. Velcrin-induced cleavage of tRNALeu(TAA) by SLFN12 and the concomitant global inhibition of protein synthesis thus define a new mechanism of apoptosis initiation. Overall design: Ribosome profiling of Hela cells treated with DMSO control or DNMDP in duplicate

Velcrin类化合物可通过诱导磷酸二酯酶3A（phosphodiesterase 3A，PDE3A）与Schlafen家族成员12（Schlafen family member 12，SLFN12）形成复合物，从而杀死高表达这两种蛋白的癌细胞，但目前尚未完全阐明PDE3A–SLFN12复合物介导癌细胞杀伤的具体分子机制。本研究发现，SLFN12核糖核酸酶的生理底物为tRNALeu(TAA)。SLFN12可选择性降解tRNALeu(TAA)，而Velcrin处理可通过体外诱导PDE3A–SLFN12复合物形成，促进tRNALeu(TAA)的切割。本研究发现，tRNALeu(TAA)的可变环与受体茎区域的特定序列是底物降解所必需的。对敏感癌细胞施加Velcrin处理后，可导致tRNALeu(TAA)表达下调、核糖体在亮氨酸TTA密码子处发生暂停，以及全局蛋白质合成受到抑制。综上，Velcrin通过诱导SLFN12切割tRNALeu(TAA)，并伴随全局蛋白质合成抑制，从而揭示了一种全新的细胞凋亡启动机制。实验整体设计：对经二甲基亚砜（DMSO）对照处理或DNMDP处理的Hela细胞进行两次生物学重复的核糖体谱分析。