PDF(Pubmed)
Abstract：
Eukaryotic translation initiation factor (eIF) 3 is a multi-subunit protein complex that binds both ribosomes and messenger RNAs (mRNAs) in order to drive a diverse set of mechanistic steps during translation. Despite its importance, a unifying framework explaining how eIF3 performs these numerous activities is lacking. Using single-molecule light scattering microscopy, we demonstrate that Saccharomyces cerevisiae eIF3 is an equilibrium mixture of the full complex, subcomplexes, and subunits. By extending our microscopy approach to an in vitro reconstituted eIF3 and complementing it with biochemical assays, we define the subspecies comprising this equilibrium and show that, rather than being driven by the full complex, mRNA binding by eIF3 is instead driven by the eIF3a subunit within eIF3a-containing subcomplexes. Our findings provide a mechanistic model for the role of eIF3 in the mRNA recruitment step of translation initiation and establish a mechanistic framework for explaining and investigating the other activities of eIF3.
摘要：
真核翻译起始因子（eIF）3是一种多亚基蛋白复合物，可结合核糖体和信使RNA（mRNA），以驱动翻译过程中的一系列机制步骤。尽管它很重要,缺乏一个统一的框架来解释eIF3如何执行这些众多活动。使用单分子光散射显微镜，我们证明酿酒酵母eIF3是完整复合物的平衡混合物，亚复合物，和子单位。通过将我们的显微镜方法扩展到体外重组的eIF3，并用生化测定来补充它，我们定义了构成这种平衡的亚种，并表明，而不是由完整的复杂驱动，eIF3的mRNA结合反而由含有eIF3a的亚复合物内的eIF3a亚基驱动。我们的发现为eIF3在翻译起始的mRNA募集步骤中的作用提供了机制模型，并建立了解释和研究eIF3其他活动的机制框架。
