Department of Molecular Medicine, Sapienza University of Rome, Viale Regina Elena 291, 00161, Rome, Italy.
Department of Biochemical Sciences "A. Rossi Fanelli", Sapienza University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy.
Cell Death Dis. 2020 Dec 10;11(12):1045. doi: 10.1038/s41419-020-03174-6.
Eukaryotic Translation Initiation Factor 5A (EIF5A) is a translation factor regulated by hypusination, a unique posttranslational modification catalyzed by deoxyhypusine synthetase (DHPS) and deoxyhypusine hydroxylase (DOHH) starting from the polyamine spermidine. Emerging data are showing that hypusinated EIF5A regulates key cellular processes such as autophagy, senescence, polyamine homeostasis, energy metabolism, and plays a role in cancer. However, the effects of EIF5A inhibition in preclinical cancer models, the mechanism of action, and specific translational targets are still poorly understood. We show here that hypusinated EIF5A promotes growth of colorectal cancer (CRC) cells by directly regulating MYC biosynthesis at specific pausing motifs. Inhibition of EIF5A hypusination with the DHPS inhibitor GC7 or through lentiviral-mediated knockdown of DHPS or EIF5A reduces the growth of various CRC cells. Multiplex gene expression analysis reveals that inhibition of hypusination impairs the expression of transcripts regulated by MYC, suggesting the involvement of this oncogene in the observed effect. Indeed, we demonstrate that EIF5A regulates MYC elongation without affecting its mRNA content or protein stability, by alleviating ribosome stalling at five distinct pausing motifs in MYC CDS. Of note, we show that blockade of the hypusination axis elicits a remarkable growth inhibitory effect in preclinical models of CRC and significantly reduces the size of polyps in APC mice, a model of human familial adenomatous polyposis (FAP). Together, these data illustrate an unprecedented mechanism, whereby the tumor-promoting properties of hypusinated EIF5A are linked to its ability to regulate MYC elongation and provide a rationale for the use of DHPS/EIF5A inhibitors in CRC therapy.
真核翻译起始因子 5A（EIF5A）是一种翻译因子，受亚精胺调控，亚精胺由脱亚精氨酸合成酶（DHPS）和脱亚精氨酸羟化酶（DOHH）从多胺精脒开始催化的一种独特的翻译后修饰。新出现的数据表明，亚精胺化的 EIF5A 调节关键的细胞过程，如自噬、衰老、多胺稳态、能量代谢，并在癌症中发挥作用。然而，EIF5A 抑制在临床前癌症模型中的效果、作用机制和特定的翻译靶标仍知之甚少。我们在这里表明，亚精胺化的 EIF5A 通过直接调节特定暂停基序中的 MYC 生物合成来促进结直肠癌（CRC）细胞的生长。用 DHPS 抑制剂 GC7 或通过慢病毒介导的 DHPS 或 EIF5A 敲低抑制 EIF5A 的亚精胺化会降低各种 CRC 细胞的生长。多重基因表达分析显示，抑制亚精胺化会损害受 MYC 调控的转录本的表达，这表明该癌基因参与了观察到的效应。事实上，我们证明 EIF5A 通过在 MYC CDS 中的五个不同暂停基序上缓解核糖体停滞来调节 MYC 的延伸，而不影响其 mRNA 含量或蛋白质稳定性。值得注意的是，我们表明阻断亚精胺化轴在 CRC 的临床前模型中产生了显著的生长抑制作用，并显著减少了 APC 小鼠（人类家族性腺瘤性息肉病（FAP）的模型）中的息肉大小。总之，这些数据说明了一种前所未有的机制，即亚精胺化的 EIF5A 的促肿瘤特性与其调节 MYC 延伸的能力有关，并为在 CRC 治疗中使用 DHPS/EIF5A 抑制剂提供了依据。
