Programmed ribosomal frameshifting is a key event during translation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA genome that allows synthesis of the viral RNA-dependent RNA polymerase and downstream proteins. Here, we present the cryo–electron microscopy structure of a translating mammalian ribosome primed for frameshifting on the viral RNA. The viral RNA adopts a pseudoknot structure that lodges at the entry to the ribosomal messenger RNA (mRNA) channel to generate tension in the mRNA and promote frameshifting, whereas the nascent viral polyprotein forms distinct interactions with the ribosomal tunnel. Biochemical experiments validate the structural observations and reveal mechanistic and regulatory features that influence frameshifting efficiency. Finally, we compare compounds previously shown to reduce frameshifting with respect to their ability to inhibit SARS-CoV-2 replication, establishing coronavirus frameshifting as a target for antiviral intervention.

程序化核糖体移码是严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) RNA 基因组翻译过程中的一个关键事件，它允许合成病毒 RNA 依赖性 RNA 聚合酶和下游蛋白质。在这里，我们展示了一种翻译哺乳动物核糖体的低温电子显微镜结构，该核糖体已准备好在病毒 RNA 上进行移码。病毒 RNA 采用假结结构，位于核糖体信使 RNA (mRNA) 通道的入口处，以在 mRNA 中产生张力并促进移码，而新生的病毒多蛋白与核糖体通道形成不同的相互作用。生化实验验证了结构观察并揭示了影响移码效率的机制和调节特征。最后，