The Journal of biological chemistry
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Coronaviruses are enveloped, single-stranded RNA viruses that are distributed worldwide. They include transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), and the human coronaviruses severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), many of which seriously endanger human health and well-being. Only alphacoronaviruses and betacoronaviruses harbor nonstructural protein 1 (nsp1), which performs multiple functions in inhibiting antiviral host responses. ⋯ Solving the crystal structure of full-length TGEV at 1.85-Å resolution and conducting several biochemical analyses, we observed that a specific motif (amino acids 91-95) of alphacoronavirus nsp1 is a conserved region that inhibits host protein synthesis. Using a reverse-genetics system based on CRISPR/Cas9 technology to construct a recombinant TGEV in which this specific nsp1 motif was altered, we found that this mutation does not affect virus replication in cell culture but significantly reduces TGEV pathogenicity in pigs. Taken together, our findings suggest that alphacoronavirus nsp1 is an essential virulence determinant, providing a potential paradigm for the development of a new attenuated vaccine based on modified nsp1.