title: Tombusvirus polymerase: Structure and function.
abstract: Tombusviruses are small icosahedral viruses that possess plus-sense RNA genomes ∼4.8kb in length. The type member of the genus, tomato bushy stunt virus (TBSV), encodes a 92kDa (p92) RNA-dependent RNA polymerase (RdRp) that is responsible for viral genome replication and subgenomic (sg) mRNA transcription. Several functionally relevant regions in p92 have been identified and characterized, including transmembrane domains, RNA-binding segments, membrane targeting signals, and oligomerization domains. Moreover, conserved tombusvirus-specific motifs in the C-proximal region of the RdRp have been shown to modulate viral genome replication, sg mRNA transcription, and trans-replication of subviral replicons. Interestingly, p92 is initially non-functional, and requires an accessory viral protein, p33, as well as viral RNA, host proteins, and intracellular membranes to become active. These and other host factors, through a well-orchestrated process guided by the viral replication proteins, mediate the assembly of membrane-associated virus replicase complexes (VRCs). Here, we describe what is currently known about the structure and function of the tombusvirus RdRp and how it utilizes host components to build VRCs that synthesize viral RNAs.
authors.affiliation: Department of Biology, York University, Toronto, Ontario, M3J 1P3, Canada.
authors.forename: Chaminda D
authors.initials: CD
authors.lastname: Gunawardene
authors.affiliation: Department of Biology, York University, Toronto, Ontario, M3J 1P3, Canada.
authors.forename: Logan W
authors.initials: LW
authors.lastname: Donaldson
authors.affiliation: Department of Biology, York University, Toronto, Ontario, M3J 1P3, Canada. Electronic address: kawhite@yorku.ca.
authors.forename: K Andrew
authors.initials: KA
authors.lastname: White
mesh_terms: D002462:Cell Membrane / Q000201:enzymology / Q000821:virology; D008970:Molecular Weight; D011485:Protein Binding; D000072417:Protein Domains; D055503:Protein Multimerization; D012367:RNA, Viral / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry* / Q000378:metabolism*; D017864:Tombusvirus / Q000201:enzymology* / Q000502:physiology*; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase
keywords: RNA replication; RNA structure; RNA synthesis; RNA virus; RNA-dependent RNA polymerase (RdRp); Tomato bushy stunt virus (TBSV); Tombusvirus; Virus replication