The Development And Mechanism Of A Novel Broad Spectrum Anti-coronavirus Inhibitor

Coronaviruses(CoVs)are enveloped single-stranded positive-sense RNA viruses in the family Coronaviridae,which own the largest known genome approximately 27～31.5 kb in length among all the RNA viruses.The Coronaviridae subfamily has been divided into four genera named Alphacoronvirus(αCoV),Betacoronavirus(βCoV),Gammacoronavirus(yCoV)and Deltacoronavirus(δCoV)based on phylogeny.TGEV,HCoV-229E,FCoV and HCoV-NL63 belong to αCoVs,and pCoVs include HCoV-OC43,MHV,SARS-CoV,HCoV-HKU1 and MERS-CoV,but IBV is aγCoV.Like eukaryotic cellular and many other viral mRNAs,the 5’ end of coronaviral RNAs also possess a cap structure which plays vital roles in RNA stability,translation initiation and evading host antiviral response.The RNA cap of coronavirus is made of an N7-methylated guanine nucleotide connected through a 5’-5’ triphosphate bridge to the first nucleotide,and this cap-0 structure(7Me GpppA...)is converted into a cap-1 structure(7MeGpppA2’-O-Me…)through 2’-O methylation of the latter.It has been demonstrated that nsp16 has S-adenosyl-L-methionine-dependent 2’-O methyltransferase(2’-OMTase)activity only interacting with nsp10 among all the CoVs except FCoV,but nsp10/16 complex activity of FCoV is much stronger than nsp16 alone.So nsp10/16 complex is a great potential broad-spectrum antiviral drug target.In this study,we design 8 peptides derived from the region of MERS-CoV nsp10 interacting with nspl6 to inhibit its 2’-O MTase activity by competitively binding nsp16 with wild-type nsp10.We find that only P21 or TCP21(the N terminus of P21 fused with a truncated HIV Tat)can inhibit nsp10/16 complex activity of ten Co Vs mentioned above in vitro and the replications of Co Vs in vivo respectively,suggesting that it may be developed a great potential broad-spectrum peptide inhibitor to treat a wide range of CoVs infection.