School of Biomedical Engineering, Guangdong Medical University, Dongguan 523808, China.
Department of Urology, Huaihe Hospital of Henan University, Kaifeng 475000, Henan, China.
Phys Chem Chem Phys. 2024 Apr 3;26(14):10660-10672. doi: 10.1039/d3cp05736d.
The cap-dependent mRNA translation is dysregulated in many kinds of cancers. The interaction between eIF4E and eIF4G through a canonical eIF4E-binding motif (CEBM) determines the efficacy of the cap-dependent mRNA translation. eIF4E-binding proteins (4E-BPs) share the CEBM and compete with eIF4G for the same binding surface of eIF4E and then inhibit the mRNA translation. 4E-BPs function as tumor repressors in nature. Hyperphosphorylation of 4E-BPs regulates the structure folding and causes the dissociation of 4E-BPs from eIF4E. However, until now, there has been no structure of the full-length 4E-BPs in complex with eIF4E. The regulation mechanism of phosphorylation is still unclear. In this work, we first investigate the interactions of human eIF4E with the CEBM and an auxiliary eIF4E-binding motif (AEBM) in eIF4G and 4E-BPs. The results unravel that the structure and interactions of the CEBM are highly conserved between eIF4G and 4E-BPs. However, the extended CEBM (ECEBM) in 4E-BPs forms a longer helix than that in eIF4G. The residue R62 in the ECEBM of 4E-BP2 forms salt bridges with E32 and E70 of eIF4E. The residue R63 of 4E-BP2 forms two special hydrogen bonds with N77 of eIF4E. Both of these interactions are missing in eIF4G. The AEBM of 4E-BPs folds into a β-sheet conformation, which protects V81 inside a hydrophobic core in 4E-BP2. In eIF4G, the AEBM exists in a random coil state. The hydrophilic residues S637 and D638 of eIF4G open the hydrophobic core for solvents. The results show that the ECEBM and AEBM may be responsible for the competing advantage of 4E-BP2. Finally, based on our previous work (J. Zeng, F. Jiang and Y. D. Wu, , 2017, , 320), the human eIF4E:4E-BP2 complex (eIF4E:BP2) including all reported phosphorylation sites is predicted. The eIF4E:BP2 complex is different from the existing experimental eIF4E:eIF4G complex and provides an important structure for further studying the regulation mechanism of phosphorylation in 4E-BPs.
帽依赖性 mRNA 翻译在多种癌症中失调。eIF4E 和 eIF4G 之间通过典型的 eIF4E 结合基序 (CEBM) 的相互作用决定了帽依赖性 mRNA 翻译的效率。eIF4E 结合蛋白 (4E-BPs) 共享 CEBM，并与 eIF4G 竞争 eIF4E 的相同结合表面，从而抑制 mRNA 翻译。4E-BPs 在自然界中作为肿瘤抑制剂发挥作用。4E-BPs 的高度磷酸化调节结构折叠并导致 4E-BPs 从 eIF4E 上解离。然而，到目前为止，还没有全长 4E-BPs 与 eIF4E 复合物的结构。磷酸化的调节机制仍不清楚。在这项工作中，我们首先研究了人 eIF4E 与 eIF4G 和 4E-BPs 中 CEBM 和辅助 eIF4E 结合基序 (AEBM) 的相互作用。结果表明，CEBM 的结构和相互作用在 eIF4G 和 4E-BPs 之间高度保守。然而，4E-BPs 中的扩展 CEBM (ECEBM) 形成的螺旋比 eIF4G 长。4E-BP2 的 ECEBM 中的残基 R62 与 eIF4E 的 E32 和 E70 形成盐桥。4E-BP2 的残基 R63 与 eIF4E 的 N77 形成两个特殊氢键。这两种相互作用在 eIF4G 中均不存在。4E-BPs 的 AEBM 折叠成β-折叠构象，将 V81 保护在 4E-BP2 的疏水核心内。在 eIF4G 中，AEBM 处于无规卷曲状态。eIF4G 的亲水残基 S637 和 D638 打开疏水核心供溶剂进入。结果表明，ECEBM 和 AEBM 可能是 4E-BP2 竞争优势的原因。最后，基于我们之前的工作 (J. Zeng, F. Jiang and Y. D. Wu,, 2017,, 320)，预测了包括所有报道的磷酸化位点的人 eIF4E:4E-BP2 复合物 (eIF4E:BP2)。eIF4E:BP2 复合物与现有的实验 eIF4E:eIF4G 复合物不同，为进一步研究 4E-BPs 中磷酸化的调节机制提供了重要结构。
