Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Toronto, Canada.
Elife. 2019 Jun 20;8:e49117. doi: 10.7554/eLife.49117.
Translation of problematic sequences in mRNAs leads to ribosome collisions that trigger a series of quality control events including ribosome rescue, degradation of the stalled nascent polypeptide, and targeting of the mRNA for decay (No Go Decay or NGD). Using a reverse genetic screen in yeast, we identify Cue2 as the conserved endonuclease that is recruited to stalled ribosomes to promote NGD. Ribosome profiling and biochemistry provide strong evidence that Cue2 cleaves mRNA within the A site of the colliding ribosome. We demonstrate that NGD primarily proceeds via Xrn1-mediated exonucleolytic decay and Cue2-mediated endonucleolytic decay normally constitutes a secondary decay pathway. Finally, we show that the Cue2-dependent pathway becomes a major contributor to NGD in cells depleted of factors required for the resolution of stalled ribosome complexes. Together these results provide insights into how multiple decay processes converge to process problematic mRNAs in eukaryotic cells..
mRNA 中问题序列的翻译会导致核糖体碰撞，从而引发一系列质量控制事件，包括核糖体救援、停滞新生多肽的降解以及 mRNA 的衰变（无义衰变或 NGD）。我们在酵母中使用反向遗传筛选，鉴定出 Cue2 是一种保守的内切核酸酶，它被招募到停滞的核糖体上，以促进 NGD。核糖体分析和生物化学提供了强有力的证据表明，Cue2 在碰撞核糖体的 A 位切割 mRNA。我们证明，NGD 主要通过 Xrn1 介导的核酸外切酶降解进行，而 Cue2 介导的内切酶降解通常构成次要的降解途径。最后，我们表明，在耗尽了用于解决停滞核糖体复合物的因子的细胞中，Cue2 依赖性途径成为 NGD 的主要贡献者。这些结果提供了对多种降解过程如何在真核细胞中集中处理有问题的 mRNA 的深入了解。
