Translating ribosomes that slow excessively incur collisions with trailing ribosomes. Persistent collisions are detected by ZNF598, a ubiquitin ligase that ubiquitinates sites on the ribosomal 40S subunit to initiate pathways of mRNA and protein quality control. The collided ribosome complex must be disassembled to initiate downstream quality control, but the mechanistic basis of disassembly is unclear. Here, we reconstitute the disassembly of a collided polysome in a mammalian cell-free system. The widely conserved ASC-1 complex (ASCC) containing the ASCC3 helicase disassembles the leading ribosome in an ATP-dependent reaction. Disassembly, but not ribosome association, requires 40S ubiquitination by ZNF598, but not GTP-dependent factors, including the Pelo-Hbs1L ribosome rescue complex. Trailing ribosomes can elongate once the roadblock has been removed and only become targets if they subsequently stall and incur collisions. These findings define the specific role of ASCC during ribosome-associated quality control and identify the molecular target of its activity.

翻译速度过慢的核糖体会与尾随的核糖体发生碰撞。ZNF598 检测持续碰撞，ZNF598 是一种泛素连接酶，泛素化核糖体 40S 亚基上的位点以启动 mRNA 和蛋白质质量控​​制途径。必须拆卸碰撞的核糖体复合物以启动下游质量控制，但拆卸的机械基础尚不清楚。在这里，我们重建了哺乳动物无细胞系统中碰撞的多核糖体的分解。包含 ASCC3 解旋酶的广泛保守的 ASC-1 复合体 (ASCC) 在 ATP 依赖性反应中分解主要核糖体。拆卸，但不是核糖体结合，需要 ZNF598 的 40S 泛素化，而不是 GTP 依赖性因素，包括 Pelo-Hbs1L 核糖体救援复合物。一旦路障被移除，尾随的核糖体就会伸长，只有在它们随后停滞并发生碰撞时才会成为目标。这些发现定义了 ASCC 在核糖体相关质量控制过程中的具体作用，并确定了其活性的分子靶点。