Sakharov P A, Sogorin E A, Agalarov S Ch, Kolb V A
Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow oblast, 142290 Russia.
Mol Biol (Mosk). 2020 May-Jun;54(3):480-486. doi: 10.31857/S0026898420030143.
The abundance of noncanonical mechanisms of eukaryotic initiation of translation indicates their involvement in the regulation of protein synthesis during key events in a cell life. One of the well-known examples of a noncanonical cap-independent process is the initiation of translation of mRNA with the 5'-untranslated (leader) region of the messenger encoding for the photoprotein obelin (the obelin leader). In the present work, mRNA with the obelin leader was modified by adding 45 deoxycytidyl nucleotides and a fluorescent label to its 5'end. Formation of the 48S ribosomal initiation complexes at the start codon of the modified mRNA was studied using primer extension inhibition (toeprinting). In contrast to mRNA with the intact obelin leader, translation initiation of which strictly requires the eIF4F factor, initiation on the modified mRNA can take place in the absence of this factor, although with less efficiency. The finding thus indicates the unknown function of the eIF4F factor in the first step(s) of mRNA recognition by ribosomal subunits.
真核生物翻译起始的非经典机制丰富多样，这表明它们参与了细胞生命关键事件中蛋白质合成的调控。非经典的不依赖帽子结构的过程中一个广为人知的例子是，信使核糖核酸（mRNA）利用编码发光蛋白奥贝林（obelin）的信使的5'-非翻译（前导）区域起始翻译（奥贝林前导序列）。在本研究中，带有奥贝林前导序列的mRNA在其5'端添加了45个脱氧胞苷核苷酸和一个荧光标记进行修饰。使用引物延伸抑制法（足迹法）研究了修饰后mRNA起始密码子处48S核糖体起始复合物的形成。与具有完整奥贝林前导序列的mRNA不同，其翻译起始严格需要eIF4F因子，而修饰后的mRNA在没有该因子的情况下也能起始翻译，尽管效率较低。这一发现因此揭示了eIF4F因子在核糖体亚基识别mRNA第一步中的未知功能。
