美国斯坦福大学Joseph D. Puglisi等研究人员合作揭示真核生物翻译启动过程中的快速40S扫描及其由mRNA结构介导的调节。相关论文于2022年11月4日在线发表在《细胞》杂志上。

通过实时单分子荧光光谱学，研究人员直接追踪了酵母43S-mRNA的结合、扫描和60S亚单位的连接。43S与mRNA的结合是通过一个缓慢的、依赖ATP的过程，由包括eIF4A在内的多种启动因子驱动。一旦接合，43S的扫描就会以每秒100个核苷酸的速度迅速发生，与核糖体装载后RNA螺旋酶的多个ATP水解循环无关。

扫描核糖体可以通过RNA二级结构进行，但是靠近起始密码子的5′非翻译区（5′UTR）发夹序列驱动起始密码子的扫描核糖体向后5′方向移动，需要重新扫描才能再次到达起始密码子。对扫描核糖体的直接观察为5′UTR结构和上游近同源起始密码子的翻译调节提供了一个机制框架。

据介绍，真核生物43S预启动复合物是如何沿着被盖住的mRNA的5′UTR扫描来定位正确的起始密码子的，这个问题仍然难以捉摸。

附：英文原文

Title: Rapid 40S scanning and its regulation by mRNA structure during eukaryotic translation initiation

Author: Jinfan Wang, Byung-Sik Shin, Carlos Alvarado, Joo-Ran Kim, Jonathan Bohlen, Thomas E. Dever, Joseph D. Puglisi

Issue&Volume: 2022-11-04

Abstract: How the eukaryotic 43S preinitiation complex scans along the 5′ untranslated region(5′ UTR) of a capped mRNA to locate the correct start codon remains elusive. Here,we directly track yeast 43S-mRNA binding, scanning, and 60S subunit joining by real-timesingle-molecule fluorescence spectroscopy. 43S engagement with mRNA occurs througha slow, ATP-dependent process driven by multiple initiation factors including thehelicase eIF4A. Once engaged, 43S scanning occurs rapidly and directionally at ～100nucleotides per second, independent of multiple cycles of ATP hydrolysis by RNA helicasespost ribosomal loading. Scanning ribosomes can proceed through RNA secondary structures,but 5′ UTR hairpin sequences near start codons drive scanning ribosomes at start codonsbackward in the 5′ direction, requiring rescanning to arrive once more at a startcodon. Direct observation of scanning ribosomes provides a mechanistic framework fortranslational regulation by 5′ UTR structures and upstream near-cognate start codons.

DOI: 10.1016/j.cell.2022.10.005

Source: https://www.cell.com/cell/fulltext/S0092-8674(22)01320-4