The evolutionarily conserved Ski2-Ski3-Ski8 (Ski) complex containing the 3'→5' RNA helicase Ski2 binds to 80S ribosomes near the mRNA entrance and facilitates 3'→5' exosomal degradation of mRNA during ribosome-associated mRNA surveillance pathways. Here, we assayed Ski's activity using an in vitro reconstituted translation system and report that this complex efficiently extracts mRNA from 80S ribosomes in the 3'→5' direction in a nucleotide-by-nucleotide manner. The process is ATP dependent and can occur on pre- and post-translocation ribosomal complexes. The Ski complex can engage productively with mRNA and extract it from 80S complexes containing as few as 19 (but not 13) 3'-terminal mRNA nucleotides starting from the P site. The mRNA-extracting activity of the Ski complex suggests that its role in mRNA quality control pathways is not limited to acceleration of exosomal degradation and could include clearance of stalled ribosomes from mRNA, poising mRNA for degradation and rendering stalled ribosomes recyclable by Pelota/Hbs1/ABCE1.

中文翻译：

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滑雪复杂从失速核糖体中提取mRNA。

包含3'→5'RNA解旋酶Ski2的进化保守的Ski2-Ski3-Ski8（Ski）复合物与mRNA入口附近的80S核糖体结合，并在与核糖体相关的mRNA监测途径中促进mRNA的3'→5'外泌体降解。在这里，我们使用体外重组翻译系统分析了Ski的活性，并报告了该复合物以核苷酸-核苷酸方式从3'→5'方向有效地从80S核糖体中提取了mRNA。该过程是ATP依赖性的，可发生在易位前和后易位核糖体复合物上。Ski复合物可以有效地与mRNA结合，并从80S复合物中提取出来，该复合物包含从P位点开始只有19个（但不是13个）3'端mRNA核苷酸。