The translational landscape of SARS-CoV-2 and infected cells

SARS-CoV-2, a betacoronavirus with a positive-sense RNA genome, has caused the ongoing COVID-19 pandemic. Although a large number of transcriptional profiling studies have been conducted in SARS-CoV-2 infected cells, little is known regarding the translational landscape of host and viral proteins. Here, using ribosome profiling in SARS-CoV-2-infected cells, we identify structural elements that regulate viral gene expression, alternative translation initiation events, as well as host responses regulated by mRNA translation. We found that the ribosome density was low within the SARS-CoV-2 frameshifting element but high immediately downstream, which suggests the utilization of a highly efficient ribosomal frameshifting strategy. In SARS-CoV-2-infected cells, although many chemokine, cytokine and interferon stimulated genes were upregulated at the mRNA level, they were not translated efficiently, suggesting a translational block that disarms host innate host responses. Together, these data reveal the key role of mRNA translation in SARS-CoV-2 replication and highlight unique mechanisms for therapeutic development.