title: Characterization of a nodavirus replicase revealed a de novo initiation mechanism of RNA synthesis and terminal nucleotidyltransferase activity.
abstract: Nodaviruses are a family of positive-stranded RNA viruses with a bipartite genome of RNAs. In nodaviruses, genomic RNA1 encodes protein A, which is recognized as an RNA-dependent RNA polymerase (RdRP) and functions as the sole viral replicase protein responsible for its RNA replication. Although nodaviral RNA replication has been studied in considerable detail, and nodaviruses are well recognized models for investigating viral RNA replication, the mechanism(s) governing the initiation of nodaviral RNA synthesis have not been determined. In this study, we characterized the RdRP activity of Wuhan nodavirus (WhNV) protein A in detail and determined that this nodaviral protein A initiates RNA synthesis via a de novo mechanism, and this RNA synthesis initiation could be independent of other viral or cellular factors. Moreover, we uncovered that WhNV protein A contains a terminal nucleotidyltransferase (TNTase) activity, which is the first time such an activity has been identified in nodaviruses. We subsequently found that the TNTase activity could function in vitro to repair the 3' initiation site, which may be digested by cellular exonucleases, to ensure the efficiency and accuracy of viral RNA synthesis initiation. Furthermore, we determined the cis-acting elements for RdRP or TNTase activity at the 3'-end of positive or negative strand RNA1. Taken together, our data establish the de novo synthesis initiation mechanism and the TNTase activity of WhNV protein A, and this work represents an important advance toward understanding the mechanism(s) of nodaviral RNA replication.
authors.affiliation: From the State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.
authors.forename: Zhaowei
authors.initials: Z
authors.lastname: Wang
authors.forename: Yang
authors.initials: Y
authors.lastname: Qiu
authors.forename: Yongxiang
authors.initials: Y
authors.lastname: Liu
authors.forename: Nan
authors.initials: N
authors.lastname: Qi
authors.forename: Jie
authors.initials: J
authors.lastname: Si
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Xia
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: Yuanyang
authors.initials: Y
authors.lastname: Hu
authors.forename: Xi
authors.initials: X
authors.lastname: Zhou
mesh_terms: D008954:Models, Biological; D030381:Nodaviridae / Q000502:physiology*; D012367:RNA, Viral / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication / Q000502:physiology*
chemical_list: D012367:RNA, Viral; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase
keywords: Nodavirus; Positive Strand RNA Viruses; RNA; RNA Viruses; RNA-dependent RNA Polymerase (RdRP); Terminal Nucleotidyltransferase (TNTase); Viral Polymerase; Viral RNA Replication; Viral Replication; de Novo Initiation
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