Ministry of Education Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, 310058 Hangzhou, China.
State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, 100850 Beijing, China.
Proc Natl Acad Sci U S A. 2019 Apr 16;116(16):7857-7866. doi: 10.1073/pnas.1813026116. Epub 2019 Apr 2.
Protein synthesis is essential for cell growth, proliferation, and survival. Protein synthesis is a tightly regulated process that involves multiple mechanisms. Deregulation of protein synthesis is considered as a key factor in the development and progression of a number of diseases, such as cancer. Here we show that the dynamic modification of proteins by O-linked β--acetyl-glucosamine (O-GlcNAcylation) regulates translation initiation by modifying core initiation factors eIF4A and eIF4G, respectively. Mechanistically, site-specific O-GlcNAcylation of eIF4A on Ser322/323 disrupts the formation of the translation initiation complex by perturbing its interaction with eIF4G. In addition, O-GlcNAcylation inhibits the duplex unwinding activity of eIF4A, leading to impaired protein synthesis, and decreased cell proliferation. In contrast, site-specific O-GlcNAcylation of eIF4G on Ser61 promotes its interaction with poly(A)-binding protein (PABP) and poly(A) mRNA. Depletion of eIF4G O-GlcNAcylation results in inhibition of protein synthesis, cell proliferation, and soft agar colony formation. The differential glycosylation of eIF4A and eIF4G appears to be regulated in the initiation complex to fine-tune protein synthesis. Our study thus expands the current understanding of protein synthesis, and adds another dimension of complexity to translational control of cellular proteins.
蛋白质合成对于细胞的生长、增殖和存活至关重要。蛋白质合成是一个受到严格调控的过程，涉及多个机制。蛋白质合成的失调被认为是许多疾病（如癌症）的发展和进展的关键因素。在这里，我们显示蛋白质的 O-连接 β-N-乙酰葡萄糖胺（O-GlcNAcylation）动态修饰通过分别修饰核心起始因子 eIF4A 和 eIF4G 来调节翻译起始。从机制上讲，eIF4A 上 Ser322/323 位点的特异性 O-GlcNAcylation 通过干扰其与 eIF4G 的相互作用，破坏翻译起始复合物的形成。此外，O-GlcNAcylation 抑制 eIF4A 的双链解旋活性，导致蛋白质合成受损和细胞增殖减少。相比之下，eIF4G 上 Ser61 位点的特异性 O-GlcNAcylation 促进其与 poly(A)-结合蛋白 (PABP) 和 poly(A) mRNA 的相互作用。eIF4G O-GlcNAcylation 的缺失导致蛋白质合成、细胞增殖和软琼脂集落形成的抑制。eIF4A 和 eIF4G 的差异糖基化似乎在起始复合物中受到调节，以微调蛋白质合成。因此，我们的研究扩展了对蛋白质合成的现有理解，并为细胞蛋白质的翻译调控增加了另一个复杂性维度。
