Structural and molecular basis of mismatch correction and ribavirin excision from coronavirus RNA.
Coronaviruses (CoVs) stand out among RNA viruses because of their unusually large genomes (∼30 kb) associated with low mutation rates. CoVs code for nsp14, a bifunctional enzyme carrying RNA cap guanine N7-methyltransferase (MTase) and 3'-5' exoribonuclease (ExoN) activities. ExoN excises nucleotide mismatches at the RNA 3'-end in vitro, and its inactivation in vivo jeopardizes viral genetic stability. Here, we demonstrate for severe acute respiratory syndrome (SARS)-CoV an RNA synthesis and proofreading pathway through association of nsp14 with the low-fidelity nsp12 viral RNA polymerase. Through this pathway, the antiviral compound ribavirin 5'-monophosphate is significantly incorporated but also readily excised from RNA, which may explain its limited efficacy in vivo. The crystal structure at 3.38 Å resolution of SARS-CoV nsp14 in complex with its cofactor nsp10 adds to the uniqueness of CoVs among RNA viruses: The MTase domain presents a new fold that differs sharply from the canonical Rossmann fold.
['Ferron|François|F|', 'Subissi|Lorenzo|L|', 'Silveira De Morais|Ana Theresa|AT|', 'Le|Nhung Thi Tuyet|NTT|', 'Sevajol|Marion|M|', 'Gluais|Laure|L|', 'Decroly|Etienne|E|', 'Vonrhein|Clemens|C|', 'Bricogne|Gérard|G|', 'Canard|Bruno|B|', 'Imbert|Isabelle|I|0000-0001-5630-9945']
D000998:Antiviral Agents D017934:Coronavirus D018360:Crystallography, X-Ray D005095:Exoribonucleases D006801:Humans D008780:Methyltransferases D008958:Models, Molecular D011485:Protein Binding D000072417:Protein Domains D012367:RNA, Viral D012254:Ribavirin D045169:Severe Acute Respiratory Syndrome D017361:Viral Nonstructural Proteins D014779:Virus Replication
ribavirin proofreading RNA virus fold evolution virus replication