Glutamyl-prolyl-tRNA synthetase (EPRS1) is a bifunctional aminoacyl-tRNA-synthetase (aaRS) essential for decoding the genetic code. EPRS1 resides, with seven other aaRSs and three noncatalytic proteins, in the cytoplasmic multi-tRNA synthetase complex (MSC). Multiple MSC-resident aaRSs, including EPRS1, exhibit stimulus-dependent release from the MSC to perform noncanonical activities distinct from their primary function in protein synthesis. Here, we show EPRS1 is present in both cytoplasm and nucleus of breast cancer cells with constitutively low phosphatase and tensin homolog (PTEN) expression. EPRS1 is primarily cytosolic in PTEN-expressing cells, but chemical or genetic inhibition of PTEN, or chemical or stress-mediated activation of its target, AKT, induces EPRS1 nuclear localization. Likewise, preferential nuclear localization of EPRS1 was observed in invasive ductal carcinoma that were also P-Ser 473 -AKT + . EPRS1 nuclear transport requires a nuclear localization signal (NLS) within the linker region that joins the catalytic glutamyl-tRNA synthetase and prolyl-tRNA synthetase domains. Nuclear EPRS1 interacts with poly(ADP-ribose) polymerase 1 (PARP1), a DNA-damage sensor that directs poly(ADP-ribosyl)ation (PARylation) of proteins. EPRS1 is a critical regulator of PARP1 activity as shown by markedly reduced ADP-ribosylation in EPRS1 knockdown cells. Moreover, EPRS1 and PARP1 knockdown comparably alter the expression of multiple tumor-related genes, inhibit DNA-damage repair, reduce tumor cell survival, and diminish tumor sphere formation by breast cancer cells. EPRS1-mediated regulation of PARP1 activity provides a mechanistic link between PTEN loss in breast cancer cells, PARP1 activation, and cell survival and tumor growth. Targeting the noncanonical activity of EPRS1, without inhibiting canonical tRNA ligase activity, provides a therapeutic approach potentially supplementing existing PARP1 inhibitors.

中文翻译：

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EPRS1 的 AKT 依赖性核定位激活乳腺癌细胞中的 PARP1


谷氨酰-脯氨酰-tRNA 合成酶 (EPRS1) 是一种双功能氨酰基-tRNA 合成酶 (aaRS)，对于解码遗传密码至关重要。 EPRS1 与其他 7 个 aaRS 和 3 个非催化蛋白一起存在于细胞质多 tRNA 合成酶复合物 (MSC) 中。多个 MSC 驻留 aaRS，包括 EPRS1，表现出 MSC 的刺激依赖性释放，以执行与其在蛋白质合成中的主要功能不同的非规范活动。在这里，我们发现 EPRS1 存在于乳腺癌细胞的细胞质和细胞核中，磷酸酶和张力蛋白同源物 (PTEN) 的表达持续较低。 EPRS1 主要存在于表达 PTEN 的细胞中，但 PTEN 的化学或遗传抑制，或其靶标 AKT 的化学或应激介导的激活，会诱导 EPRS1 核定位。同样，在同样为 P-Ser 473 -AKT + 的浸润性导管癌中观察到 EPRS1 的优先核定位。 EPRS1 核转运需要连接区域内的核定位信号 (NLS)，该信号连接催化谷氨酰-tRNA 合成酶和脯氨酰-tRNA 合成酶结构域。核 EPRS1 与聚（ADP-核糖）聚合酶 1 (PARP1) 相互作用，聚（ADP-核糖）聚合酶 1 (PARP1) 是一种 DNA 损伤传感器，可指导蛋白质的聚（ADP-核糖）化（PARylation）。 EPRS1 是 PARP1 活性的关键调节因子，EPRS1 敲除细胞中 ADP 核糖基化显着降低即可证明。此外，EPRS1和PARP1敲除会改变多个肿瘤相关基因的表达，抑制DNA损伤修复，降低肿瘤细胞存活率，并减少乳腺癌细胞形成肿瘤球。 EPRS1 介导的 PARP1 活性调节提供了乳腺癌细胞中 PTEN 缺失、PARP1 激活以及细胞存活和肿瘤生长之间的机制联系。 靶向 EPRS1 的非经典活性，而不抑制经典 tRNA 连接酶活性，提供了一种可能补充现有 PARP1 抑制剂的治疗方法。