核糖体蛋白
核糖体
核糖体RNA
生物
5S核糖体RNA
泛素
细胞生物学
蛋白质生物合成
蛋白质降解
生物化学
基因
核糖核酸
作者
Donghong Ju,Li Li,Youming Xie
标识
DOI:10.1073/pnas.2306152120
摘要
Ribosomes are the workplace for protein biosynthesis. Protein production required for normal cell function is tightly linked to ribosome abundance. It is well known that ribosomal genes are actively transcribed and ribosomal messenger RNAs (mRNAs) are rapidly translated, and yet ribosomal proteins have relatively long half-lives. These observations raise questions as to how homeostasis of ribosomal proteins is controlled. Here, we show that ribosomal proteins, while posttranslationally stable, are subject to high-level cotranslational protein degradation (CTPD) except for those synthesized as ubiquitin (Ub) fusion precursors. The N-terminal Ub moiety protects fused ribosomal proteins from CTPD. We further demonstrate that cotranslational folding efficiency and expression level are two critical factors determining CTPD of ribosomal proteins. Different from canonical posttranslational degradation, we found that CTPD of all the ribosomal proteins tested in this study does not require prior ubiquitylation. This work provides insights into the regulation of ribosomal protein homeostasis and furthers our understanding of the mechanism and biological significance of CTPD.
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