Tomomatsu Shota, Matsuo Yoshitaka, Ohtake Fumiaki, Tomita Takuya, Saeki Yasushi, Inada Toshifumi
Division of RNA and Gene Regulation, Institute of Medical Science, The University of Tokyo, Minato-Ku, 108-8639, Japan.
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-Ku, Tokyo, Japan.
EMBO J. 2025 Sep 16. doi: 10.1038/s44318-025-00568-0.
In ribosome-associated quality control (RQC), K63-linked polyubiquitination of ribosomal protein uS10 on the stalled ribosome is crucial for recruiting the RQC-trigger (RQT) complex. However, the mechanisms governing the maintenance and recycling of polyubiquitin architecture on colliding ribosomes remain unclear. Here we demonstrate that two deubiquitinating enzymes (DUBs), Ubp2 and Ubp3, play key roles in editing and recycling polyubiquitin chains on yeast uS10, thereby contributing to the promotion of RQC activity. Specifically, Ubp2 eliminates K63-linked polyubiquitin chains from uS10 on the free 40S subunit for recycling, while Ubp3 predominantly cleaves K48-linked di-ubiquitin and K48/K63-mixed-linkage polyubiquitin chains from uS10 on the translating ribosomes. We further demonstrate that K48-linkage-containing ubiquitin chains on uS10 of the colliding ribosome act as a negative signal for the RQT-mediated ribosome dissociation process. Collectively, our findings provide insight into the ubiquitin code in RQC, and define positive functions of two DUBs in maintaining persistent RQC activity.
在核糖体相关质量控制（RQC）中，停滞核糖体上核糖体蛋白uS10的K63连接的多聚泛素化对于招募RQC触发因子（RQT）复合物至关重要。然而，关于碰撞核糖体上多聚泛素结构的维持和循环利用机制仍不清楚。在此，我们证明两种去泛素化酶（DUBs），Ubp2和Ubp3，在编辑和循环利用酵母uS10上的多聚泛素链中起关键作用，从而有助于促进RQC活性。具体而言，Ubp2从游离40S亚基上的uS10去除K63连接的多聚泛素链以供循环利用，而Ubp3主要从正在翻译的核糖体上的uS10切割K48连接的二聚泛素和K48/K63混合连接的多聚泛素链。我们进一步证明，碰撞核糖体uS10上含K48连接的泛素链作为RQT介导的核糖体解离过程的负信号。总之，我们的发现为RQC中的泛素密码提供了见解，并定义了两种DUBs在维持持续RQC活性中的积极作用。
