Mononegavirales

Mononegavirales is an order of negative-strand RNA viruses which have nonsegmented genomes. Some members that cause human disease in this order include Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah virus, and rabies virus. Important pathogens of nonhuman animals and plants are also in the group. The order includes eleven virus families: Artoviridae, Bornaviridae, Filoviridae, Lispiviridae, Mymonaviridae, Nyamiviridae, Paramyxoviridae, Pneumoviridae, Rhabdoviridae, Sunviridae, and Xinmoviridae.<ref name=":0" />

Use of term

The order Mononegavirales (pronounced: Template:IPAc-en Template:Respell) <ref group=note>According to the rules for taxon naming established by the International Committee on Taxonomy of Viruses (ICTV), the name Mononegavirales is always to be capitalized, italicized, and never abbreviated. The names of the order's physical members ("mononegaviruses" or "mononegavirads") are to be written in lower case, are not italicized, and used without articles.</ref><ref name=King2011/><ref name=KuhnArch/> is a virological taxon that was created in 1991<ref name=Pringle1991>Template:Cite journal</ref><ref>Template:Cite book</ref> and amended in 1995,<ref>Template:Cite book</ref> 1997,<ref name=Pringle1997>Template:Cite journal</ref> 2000,<ref>Template:Cite book</ref> 2005,<ref name=Fauquet2005>Template:Cite book</ref> 2011,<ref name=King2011>Template:Cite book</ref> 2016,<ref>Template:Cite journal</ref> 2017,<ref>Template:Cite journal</ref> and 2018.<ref name=":0">Template:Cite journal</ref> The name Mononegavirales is derived from the Ancient Greek adjective μóνος monos (alluding to the monopartite and single-stranded genomes of most mononegaviruses), the Latin verb negare (alluding to the negative polarity of these genomes), and the taxonomic suffix -virales (denoting a viral order).<ref name="KuhnArch">Template:Cite journal</ref>

Order inclusion criteria

The genome organization and RNA synthesis of order Mononegavirales

A virus is a member of the order Mononegavirales if<ref name="King2011" /><ref name="KuhnArch" />

• its genome is a linear, typically (but not always) nonsegmented, single-stranded, non-infectious RNA of negative polarity; possesses inverse-complementary 3' and 5' termini; and is not covalently linked to a protein;
• its genome has the characteristic gene order 3'-UTR–core protein genes–envelope protein genes–RNA-dependent RNA polymerase gene–5'-UTR (3'-N-P-M-G-L-5') (there are, however, some exceptions);
• it produces 5–10 distinct mRNAs from its genome via polar sequential transcription from a single promoter located at the 3' end of the genome; mRNAs are 5' capped and polyadenylated;
• it replicates by synthesizing complete antigenomes;
• it forms infectious helical ribonucleocapsids as the templates for the synthesis of mRNAs, antigenomes, and genomes;
• it encodes an RNA-dependent RNA polymerase (RdRp, L) that is highly homologous to those of other mononegaviruses; and/or
• it typically (but not always) produces enveloped virions with a molecular mass of 300–1,000Template:E; an S_20W of 550–>1,045; and a buoyant density in CsCl of 1.18–1.22 g/cm³.

Life cycle

Life cycle of vesiculoviruses

The mononegavirus life cycle begins with virion attachment to specific cell-surface receptors, followed by fusion of the virion envelope with cellular membranes and the concomitant release of the virus nucleocapsid into the cytosol. The virus RdRp partially uncoats the nucleocapsid and transcribes the genes into positive-stranded mRNAs, which are then translated into structural and nonstructural proteins.<ref name="Fauquet2005" />

Mononegavirus RdRps bind to a single promoter located at the 3' end of the genome. Transcription either terminates after a gene or continues to the next gene downstream. This means that genes close to the 3' end of the genome are transcribed in the greatest abundance, whereas those toward the 5' end are least likely to be transcribed. The gene order is therefore a simple but effective form of transcriptional regulation. The most abundant protein produced is the nucleoprotein, whose concentration in the cell determines when the RdRp switches from gene transcription to genome replication.<ref name="Fauquet2005" />

Replication results in full-length, positive-stranded antigenomes that are in turn transcribed into negative-stranded virus progeny genome copies. Newly synthesized structural proteins and genomes self-assemble and accumulate near the inside of the cell membrane. Virions bud off from the cell, gaining their envelopes from the cellular membrane they bud from. The mature progeny particles then infect other cells to repeat the cycle.<ref name="Fauquet2005" />

Paleovirology

Mononegavirales phylogenetic tree

Mononegaviruses have a history that dates back several tens of millions of years. Mononegavirus "fossils" have been discovered in the form of mononegavirus genes or gene fragments integrated into mammalian genomes. For instance, bornavirus gene "fossils" have been detected in the genomes of bats, fish, hyraxes, marsupials, primates, rodents, ruminants, and elephants.<ref name="Horie2010">Template:Cite journal</ref><ref name="Belyi2010">Template:Cite journal</ref><ref name="Katzourakis2010">Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Filovirus gene "fossils" have been detected in the genomes of bats, rodents, shrews, tenrecs, and marsupials.<ref name="Belyi2010" /><ref name="Katzourakis2010" /><ref name="Taylor2010">Template:Cite journal</ref><ref>Template:Cite journal</ref> A Midway virus "fossil" was found in the genome of zebrafish.<ref name="Belyi2010" /> Finally, rhabdovirus "fossils" were found in the genomes of crustaceans, mosquitoes, ticks, and plants.<ref>Template:Cite journal</ref><ref name="Katzourakis2010" /><ref name="Chiba2011">Template:Cite journal</ref><ref name="Ford2012">Template:Cite journal</ref>

Taxonomy

The order contains the following eleven families:<ref>Template:Cite web</ref> Template:Div col

• Artoviridae
• Bornaviridae
• Filoviridae
• Lispiviridae
• Mymonaviridae
• Nyamiviridae
• Paramyxoviridae
• Pneumoviridae
• Rhabdoviridae
• Sunviridae
• Xinmoviridae

External links

• International Committee on Taxonomy of Viruses (ICTV)