A second, non-canonical RNA-dependent RNA polymerase in SARS coronavirus.
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Imbert I, Guillemot JC, Bourhis JM, Bussetta C, Coutard B, Egloff MP, Ferron F, Gorbalenya AE, Canard B
A second, non-canonical RNA-dependent RNA polymerase in SARS coronavirus.
EMBO J. 2006 Oct 18;25(20):4933-42. Epub 2006 Oct 5.
- PubMed ID
- 17024178 [ View in PubMed]
- Abstract
In (+) RNA coronaviruses, replication and transcription of the giant approximately 30 kb genome to produce genome- and subgenome-size RNAs of both polarities are mediated by a cognate membrane-bound enzymatic complex. Its RNA-dependent RNA polymerase (RdRp) activity appears to be supplied by non-structural protein 12 (nsp12) that includes an RdRp domain conserved in all RNA viruses. Using SARS coronavirus, we now show that coronaviruses uniquely encode a second RdRp residing in nsp8. This protein strongly prefers the internal 5'-(G/U)CC-3' trinucleotides on RNA templates to initiate the synthesis of complementary oligonucleotides of <6 residues in a reaction whose fidelity is relatively low. Distant structural homology between the C-terminal domain of nsp8 and the catalytic palm subdomain of RdRps of RNA viruses suggests a common origin of the two coronavirus RdRps, which however may have evolved different sets of catalytic residues. A parallel between the nsp8 RdRp and cellular DNA-dependent RNA primases is drawn to propose that the nsp8 RdRp produces primers utilized by the primer-dependent nsp12 RdRp.