Coronavirus nsp10/nsp16 Methyltransferase Can Be Targeted by nsp10-Derived Peptide In Vitro and In Vivo To Reduce Replication and Pathogenesis

Abstract

The 5= cap structures of eukaryotic mRNAs are important for RNA stability and protein translation. T he 5= ends of eukaryotic cellular mRNAs and most viral mRNAs possess a cap structure, which plays important roles in mRNA splicing, intracellular RNA transport, RNA stability, and translation initiation (1). Host and viral RNA molecules lacking the 5= cap structure are rapidly degraded in the cytoplasm (2). The cap-0 structure of mRNA is cotranscriptionally formed through sequential enzymatic reactions, including RNA triphosphatase (TPase), RNA guanylyltransferase (GTase), and RNA (guanine-N7)-methyltransferase (N7-MTase) (1). In higher eukaryotes and some viruses, cap-0 structure m7GpppN-RNA is further methylated at the ribose 2=-O position of the nascent mRNA by a ribose 2=-O-methyltransferase (2=-O-MTase) to form a cap-1 structure (m7GpppNm) and cap-2 structure (m7GpppNmNm). Both N7-MTase and 2=-O-MTase can catalyze the transfer of the methyl group from the methyl donor S-adenosyl-L-methionine (SAM or AdoMet) to RNA substrate and generate S-adenosyl-L-homocysteine (SAH or AdoHcy) as a by-product. The functions of viral RNA cap structure include the following: (i) the guanosine cap core structure protects the 5=-triphosphate from activating the host innate immune response (3, 4); (ii) the N7 methylation is essential for viral replication through the enhancement of viral RNA translation (5); and (iii) the 2=-O methylation functions to

Identification of an infectious bronchitis coronavirus strain exhibiting a classical genotype but altered antigenicity, pathogenicity, and innate immunity profile

“…It has been shown that a natural recombinant strain containing partial nsp regions from a low pathogenic H120 strain in the frame of a nephropathogenic strain possesses attenuated pathogenicity, which suggests strong associations between nsps and IBV virulence39. Studies on other coronaviruses such as MHV and severe acute respiratory syndrome coronavirus (SARS-CoV) have also shown that nsps are associated with viral replication and evasion of host innate immune response via viral RNA modification4041, host mRNA degradation, and IFN antagonist competition42. Therefore, given the low sequence homology in the accessory proteins 3a, 3b, and 5b between IBV 3575/08 and 2575 WT, we conjecture that these accessary proteins contribute to the blockade of PRR expressions, delayed immune response, and enhanced virulence of IBV 3575/08 in the present study.…”

Identification and Characterization of a Ribose 2′- O -Methyltransferase Encoded by the Ronivirus Branch of Nidovirales

“…Generation of 2=-O-MTase-deficient viruses has been used as a strategy to develop effective live attenuated vaccines (9)(10)(11)(12). Chemical and polypeptide inhibitors targeting viral 2=-O-MTase have been shown to function as antivirals (13)(14)(15).…”

The Nonstructural Proteins Directing Coronavirus RNA Synthesis and Processing

“…Interestingly, the nsp10 residues involved in the nsp10/nsp16 interaction are quite conserved within the CoV family and it was recently demonstrated that nsp10 of different CoVs (FCoV, MHV, SARS-CoV, MERS-CoV) is functionally interchangeable in the stimulation of nsp16 2 0 -O-MTase activity . Thus, molecules or peptides blocking this interface may have broad-spectrum anti-CoV effects, a concept that was explored and supported using synthetic peptides that mimic the nsp10 interface and suppress nsp16 2 0 -O-MTase activity in vitro (Ke et al, 2012;Wang et al, 2015). The antiviral effect of the MHV TP29 peptide, for example, was first demonstrated in MHV-infected cells and was subsequently confirmed to limit MHV replication in mice and to enhance the type I interferon response .…”