北京大学Ning Gao团队近期取得重要工作进展。他们进行了人类pre-60S核糖体颗粒核质成熟的可视化研究。相关研究成果2023年7月25日在线发表于《细胞—研究》杂志上。

据介绍，真核核糖体组装是一个高度协调的过程，涉及200多种蛋白质因子。在核仁中新生rRNA的早期组装事件之后，pre-60S颗粒在核质中经历连续的成熟步骤，并为核输出做准备。

研究人员报道了通过表位标记的GNL2从人类细胞中分离的核pre-60S颗粒的11个冷冻EM结构，分辨率为2.8–4.3 Å。这些高分辨率快照以虚拟的时间分辨率为几个主要的结构重塑事件提供了精细的细节。研究人员还发现了两种新的人类核因子L10K和C11orf98。比较结构分析表明，许多组装因子作为连续的占位符来控制因子关联/分离事件的时间。它们对不同结构域显示出多相结合特性，并产生复杂的结合相互依赖性，作为引导rRNA成熟过程走向成熟构象的一种手段。

总之，这一研究表明，人类pre-60S颗粒的核组装通常具有短分支通路的分级性，一些因素通过局部限制rRNA螺旋以促进其折叠而显示出作为rRNA伴侣的特定作用，例如SDAD1的C末端结构域。

附：英文原文

Title: Visualizing the nucleoplasmic maturation of human pre-60S ribosomal particles

Author: Zhang, Yunyang, Liang, Xiaomeng, Luo, Sha, Chen, Yan, Li, Yu, Ma, Chengying, Li, Ningning, Gao, Ning

Issue&Volume: 2023-07-25

Abstract: Eukaryotic ribosome assembly is a highly orchestrated process that involves over two hundred protein factors. After early assembly events on nascent rRNA in the nucleolus, pre-60S particles undergo continuous maturation steps in the nucleoplasm, and prepare for nuclear export. Here, we report eleven cryo-EM structures of the nuclear pre-60S particles isolated from human cells through epitope-tagged GNL2, at resolutions of 2.8–4.3. These high-resolution snapshots provide fine details for several major structural remodeling events at a virtual temporal resolution. Two new human nuclear factors, L10K and C11orf98, were also identified. Comparative structural analyses reveal that many assembly factors act as successive place holders to control the timing of factor association/dissociation events. They display multi-phasic binding properties for different domains and generate complex binding inter-dependencies as a means to guide the rRNA maturation process towards its mature conformation. Overall, our data reveal that nuclear assembly of human pre-60S particles is generally hierarchical with short branch pathways, and a few factors display specific roles as rRNA chaperones by confining rRNA helices locally to facilitate their folding, such as the C-terminal domain of SDAD1.

DOI: 10.1038/s41422-023-00853-9

Source: https://www.nature.com/articles/s41422-023-00853-9