The fission yeast Schizosaccharomyces pombe has two tRNase Z^L genes (trz1 and trz2) involved in nuclear and mitochondrial tRNA 3′-end processing, respectively. Overexpression of trz2 but not trz1 is toxic to cells. In the present work, we showed that trz2 overexpression led to apoptotic cell death, as revealed by DAPI and Annexin V-FITC staining. Overexpression of trz2 also caused a loss of mitochondrial membrane potential and an increased reactive oxygen species (ROS) formation. These effects required mitochondrial localization but not its catalytic activity. RNA sequencing (RNA-seq) analysis revealed increased expression levels of genes involved in iron uptake and/or iron homeostasis, suggesting an elevated level of intracellular iron in the trz2-overexpressing cells. Indeed, we showed that overexpressing trz2 increased the level of intracellular iron by ∼2-fold. We further showed that the iron chelator, bathophenanthroline disulfonic acid (BPS) nearly restored the viability of trz2-overexpression cells and reduced ROS levels in the cells. These results suggest that trz2 overexpression may cause mitochondrial dysfunction, which is likely to lead to perturbation of iron homeostasis, ROS accumulation and induction of apoptotic cell death in S. pombe.

裂变酵母粟酒裂殖酵母具有两个分别参与核和线粒体tRNA 3'末端加工的tRNase Z ^L基因（trz1和trz2）。trz2的过度表达但对trz1的过度表达对细胞有毒。在目前的工作中，我们证明了trz2如DAPI和Annexin V-FITC染色所揭示的，过表达导致凋亡性细胞死亡。trz2的过表达还导致线粒体膜电位的丧失和活性氧（ROS）形成的增加。这些作用需要线粒体定位，而不是其催化活性。RNA测序（RNA-seq）分析显示，参与铁摄取和/或铁稳态的基因表达水平增加，表明过表达trz2的细胞内细胞内铁水平升高。确实，我们表明过表达trz2使细胞内铁水平增加了约2倍。我们进一步表明，铁螯合剂，邻菲咯啉二磺酸（BPS）几乎恢复了trz2的生存能力-过表达细胞并降低细胞中的ROS水平。这些结果表明trz2的过表达可能导致线粒体功能障碍，这可能导致铁稳态的扰动，ROS的积累和诱导粟酒裂殖酵母的凋亡细胞死亡。