National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Mol Cell. 2020 Aug 20;79(4):588-602.e6. doi: 10.1016/j.molcel.2020.06.010. Epub 2020 Jul 1.
The ribosome-associated protein quality control (RQC) system that resolves stalled translation events is activated when ribosomes collide and form disome, trisome, or higher-order complexes. However, it is unclear whether this system distinguishes collision complexes formed on defective mRNAs from those with functional roles on endogenous transcripts. Here, we performed disome and trisome footprint profiling in yeast and found collisions were enriched on diverse sequence motifs known to slow translation. When 60S recycling was inhibited, disomes accumulated at stop codons and could move into the 3' UTR to reinitiate translation. The ubiquitin ligase and RQC factor Hel2/ZNF598 generally recognized collisions but did not induce degradation of endogenous transcripts. However, loss of Hel2 triggered the integrated stress response, via phosphorylation of eIF2α, thus linking these pathways. Our results suggest that Hel2 has a role in sensing ribosome collisions on endogenous mRNAs, and such events may be important for cellular homeostasis.
核糖体相关的蛋白质量控制系统（RQC）能够解决翻译暂停事件，当核糖体碰撞并形成二联体、三联体或更高阶复合物时，该系统就会被激活。然而，目前尚不清楚该系统是否能够区分在有缺陷的 mRNA 上形成的碰撞复合物与在内源性转录本上具有功能作用的复合物。在这里，我们在酵母中进行了二联体和三联体足迹分析，发现碰撞在已知能减缓翻译的各种序列基序上富集。当 60S 循环被抑制时，二联体在终止密码子处积累，并可以进入 3'UTR 重新起始翻译。泛素连接酶和 RQC 因子 Hel2/ZNF598 通常识别碰撞，但不会诱导内源性转录本的降解。然而，Hel2 的缺失会通过磷酸化 eIF2α 触发整合应激反应，从而将这些途径联系起来。我们的研究结果表明，Hel2 在识别内源性 mRNA 上的核糖体碰撞方面具有作用，而这些事件可能对内源性 mRNAs 的细胞内稳态很重要。
