Significance SARS-CoV-2 is the causative agent of the COVID-19 pandemic. A molecular framework for how the virus manipulates host cellular machinery to facilitate infection is needed. Here, we integrate biochemical and single-molecule strategies to reveal molecular insight into how NSP1 from SARS-CoV-2 inhibits translation initiation. NSP1 directly binds to the small (40S) subunit of the human ribosome, which is modulated by human initiation factors. Further, NSP1 and mRNA compete with each other to bind the ribosome. Our findings suggest that the presence of NSP1 on the small ribosomal subunit prevents proper accommodation of the mRNA. How this competition disrupts the many steps of translation initiation is an important target for future studies. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a beta-CoV that recently emerged as a human pathogen and is the causative agent of the COVID-19 pandemic. A molecular framework of how the virus manipulates host cellular machinery to facilitate infection remains unclear. Here, we focus on SARS-CoV-2 NSP1, which is proposed to be a virulence factor that inhibits protein synthesis by directly binding the human ribosome. We demonstrate biochemically that NSP1 inhibits translation of model human and SARS-CoV-2 messenger RNAs (mRNAs). NSP1 specifically binds to the small (40S) ribosomal subunit, which is required for translation inhibition. Using single-molecule fluorescence assays to monitor NSP1–40S subunit binding in real time, we determine that eukaryotic translation initiation factors (eIFs) allosterically modulate the interaction of NSP1 with ribosomal preinitiation complexes in the absence of mRNA. We further elucidate that NSP1 competes with RNA segments downstream of the start codon to bind the 40S subunit and that the protein is unable to associate rapidly with 80S ribosomes assembled on an mRNA. Collectively, our findings support a model where NSP1 proteins from viruses in at least two subgenera of beta-CoVs associate with the open head conformation of the 40S subunit to inhibit an early step of translation, by preventing accommodation of mRNA within the entry channel.
【저자키워드】 SARS-CoV-2, nsp1, human ribosome, eukaryotic translation initiation, single-molecule fluorescence, 【초록키워드】 severe acute respiratory syndrome coronavirus 2, viruses, coronavirus, translation, COVID-19 pandemic, Infection, severe acute respiratory syndrome Coronavirus, virus, RNA, Protein, mRNA, Factors, nsp1, molecular, respiratory, virulence, binding, ribosome, cellular, Interaction, mRNAs, protein synthesis, real time, open, focus, causative agent, virulence factor, initiation factors, Support, Messenger RNA, acute respiratory syndrome, Factor, biochemical, subunit, acute respiratory syndrome coronavirus, human pathogen, MONITOR, downstream, accommodation, beta-CoVs, ribosomal subunit, SARS-CoV-2 NSP1, start codon, translation initiation, Host, Prevent, bind, inhibit, required, facilitate, determine, absence, modulate, biochemically, complexes, eukaryotic translation, disrupt, 40S, modulated, beta-CoV, Significance, 【제목키워드】 dynamic, inhibit,