Nidovirales
Nidovirales | |
---|---|
Life cycle of nidoviruses | |
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Pisuviricota |
Class: | Pisoniviricetes |
Order: | Nidovirales |
Nidovirales is an order of
Member viruses have a viral envelope and a positive-sense, single-stranded RNA genome which is capped and polyadenylated.[3] Nidoviruses are named for the Latin nidus, meaning nest, as all viruses in this order produce a 3' co-terminal nested set of subgenomic mRNAs during infection.[4]
Virology
Structure
Nidoviruses have a viral envelope and a positive-sense, single-stranded RNA genome which is capped and polyadenylated.[3] The group expresses structural proteins separately from the nonstructural ones. The structural proteins are encoded at the 3' region of the genome and are expressed from a set of subgenomic mRNAs.[citation needed]
Member viruses encode one main
Genome
Nidoviruses can be distinguished from other RNA viruses by a constellation of seven conserved domains—5'-TM2-3CLpro-TM3-RdRp-Zm-HEL1-NendoU-3'—with the first three being encoded in
Most, but not all, nidovirus subgenomic RNAs contain a 5′ leader sequence derived from the 5′ end of the genomic RNA. The frameshift that generates ORF1b frameshift occurs at a UUUAAAC heptanucleotide 'slippery' sequence located upstream of the ORF1a stop codon and a putative RNA pseudoknot structure.[citation needed]
Many proteins have been identified on the genomes of Nidovirales, but their function has not yet been determined. Other enzymes that may be present in the genome include papain-like proteases, ADP-ribose/poly(ADP-ribose)-binding or ADP-ribose 1''-phosphate phosphatase activities and cyclic nucleotide phosphodiesterase.[citation needed]
Phylogenetics
The order Nidovirales can be divided into two clades depending on the size of the genome: those with large genomes (26.3–31.7 kilobases) which included the Coronaviridae and Roniviridae (the large nidoviruses) and those with small genomes (the small nidoviruses)—a clade that includes the distantly related Arteriviridae (12.7–15.7 kb).[citation needed]
The large nidoviruses encode both a 2'-O-methyltransferase and a 3'–5' exoribonuclease (ExoN)—the latter being very unusual for an RNA virus. They also encode a superfamily 1 helicase, uridylate-specific endonuclease (an enzyme unique to nidoviruses) and several proteases.[citation needed]
Nidoviruses as a group have the largest RNA genomes of viruses. Group member planarian secretory cell nidovirus (PSCNV) has the largest known nonsegmented RNA genome of 41.1kb.[6] Its host is the planarian flatworm.[7]
Taxonomy
The following suborders and families are recognized (-virineae denotes
- Abnidovirineae
- Abyssoviridae
- Arnidovirineae
- Cornidovirineae
- Mesnidovirineae
- Monidovirineae
- Mononiviridae
- Nanidovirinae
- Ronidovirineae
- Euroniviridae
- Roniviridae
- Tornidovirineae
See also
- Animal viruses
- Coronaviruses
- Serpentoviruses
References
- PMID 31440227.
- ^ "International Committee on Taxonomy of Viruses (ICTV)". talk.ictvonline.org. Retrieved 2020-06-08.
- ^ S2CID 218627729, retrieved 2020-06-08
- S2CID 85383257.
- PMID 33413979.
- ^ "Taxonomy browser (Planidovirus 1)". www.ncbi.nlm.nih.gov. Retrieved 2020-06-08.
- PMID 30383829.
- ^ "Virus Taxonomy: 2019 Release". talk.ictvonline.org. International Committee on Taxonomy of Viruses. Retrieved 30 April 2020.
- Ziebuhr, J; Snijder, EJ; Gorbalenya, AE (April 2000). "Virus-encoded proteinases and proteolytic processing in the Nidovirales". The Journal of General Virology. 81 (Pt 4): 853–79. PMID 10725411.
External links
- Nidovirales—ICTVdB—The Universal Virus Database, version 4.
- Nidovirales at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- NIH/MeSH
- "The Nidoviruses" ISBN 0306466341