Negative-sense single-stranded RNA virus

Negative ssRNA Virus
	Ebola Virus
Virus classification
Group:	Group V ((−)ssRNA)
Order, family y genus
	Order Mononegavirales Family Bornaviridae; Family Filoviridae; Family Paramyxoviridae; Family Rhabdoviridae; ; Unassigned families: Family Arenaviridae; Family Bunyaviridae; Family Orthomyxoviridae; ; Unassigned genera: Genus Deltavirus; Genus Ophiovirus; Genus Tenuivirus; Genus Varicosavirus; ;

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This article is currently under construction. Please do not move until April 21, 2015.

Memo:

I wanted to use this assignment as an opportunity to practice my Spanish, so I decided to search for an article to translate. The wiki page containing science articles that need translating from Spanish Wikipedia only has topics relating to trees and flowers, which is far from my topic of interest. Instead, I used this tool to look for articles that are in Spanish but has no interwiki link to English. I came upon the page for (-)ssRNA virus and tried to find the English equivalent article. Currently, there is no page for (-)ssRNA virus but there are small sections about the topic on the pages RNA virus and Sense (molecular biology). However, there is no substantial information on this topic on these pages. Even the section on (+)ssRNA virus has more information. This is why I think this is a good topic to have its own separate page, where the information from other articles are compiled in one place. Currently, this page is a straight up translation and I will add in information from the other pages after asking on the respective Talk sections. I may add in extra text from the links below.

Extra (-)ssRNA virus stuff:

http://www.pnas.org/content/110/45/E4238.abstract

http://www.worldscientific.com/worldscibooks/10.1142/7832#t=aboutBook

http://jvi.asm.org/content/88/7/3766.abstract

Negative-Sense Single Strand RNA Viruses

A negative single strand RNA virus (or ss(-)RNA virus) is a virus with negative sense RNA as genetic material and does not replicate with a DNA intermediate. These viruses belong to Group V on the Baltimore Classification ^[1]. It is part of the single stranded RNA virus class, which are classifiable as negative or positive depending on the sense or polarity of the RNA. The negative viral RNA is complementary to the mRNA and must be converted to a positive RNA by RNA polymerase before transcription. The purified RNA of a negative sense virus is not infectious by itself, as it needs to be converted to a positive sense RNA.

Taxonomy?

There is one order and eight families recognised in this group. There are also a number of unassigned species and genera.

Order Mononegavirales
- Family Bornaviridae—Borna disease virus
- Family Filoviridae—includes Ebola virus, Marburg virus
- Family Paramyxoviridae—includes Measles virus, Mumps virus, Nipah virus, Hendra virus, RSV and NDV
- Family Rhabdoviridae—includes Rabies virus
- Family Nyamiviridae—includes Nyavirus

Unassigned families:
- Family Arenaviridae—includes Lassa virus
- Family Bunyaviridae—includes Hantavirus, Crimean-Congo hemorrhagic fever
- Family Ophioviridae
- Family Orthomyxoviridae—includes Influenza viruses

Unassigned genera:
- Genus Deltavirus—includes Hepatitis D virus
- Genus Dichorhavirus
- Genus Emaravirus
- Genus Nyavirus^[2]—includes Nyamanini and Midway viruses
- Genus Tenuivirus
- Genus Varicosavirus

Unassigned species:
- Taastrup virus
- Sclerotinia sclerotiorum negative-stranded RNA virus 1

^[3]

Replication

When a virion enters the host cell, it uncoats to release the negative RNA strand in cytoplasm. RNA polymerase makes template strands through complementary base pairings. These template strands are translated into capsomere proteins. These proteins are used to assemble new virals capsids. New negative RNA strands are also produced from these template strands, which combine with the capsids to make new negative stranded RNA virions [1].

The virion brings its own RNA replicase, which is a RNA-dependent RNA polymerase (RdRp) to the cell. Viral RdRp makes positive-sense single strands of RNA from the negative-sense RNA. The positive-sense strand is used as mRNA to make structural proteins (capsid) and more viral RdRp. The new RdRp makes a replicative complex and more positive-sense RNA. The positive sense RNA either acts as mRNA for proteins or used as template for more negative sense RNA. The negative RNA, viral RdRp, and structural proteins join to form virions. These virions exit cell by budding or lysis. [2]

Negative sense RNA virus use a RNA polymerase or transcriptase to form a positive sense RNA. The virus must contain the RNA polymerase enzyme. The formed positive sense RNA molecule then acts as a viral mRNA, which is translated into proteins by the hosts' ribosomes. The resulting proteins are directly used for the production of materials to make new virions, such as capsid proteins and RNA replicase. These virions will further produce new negative sense RNA molecules.

Replication of the virus consists of the following steps:^[4]

1. Early transcription of negative sense RNA by RNA polymerase. This is dependent on the RNA inside the virion, principal production of subgenomic mRNA, and the positive single strand RNA. This step occurs in the cytoplasm and gives way to the formation of the replication complex.

2. Translation of mRNA, production and accumulation of early regulatory proteins.

3. Regulatory proteins interact with the replication complex, promoting the positive single strand RNA production and thus, the genomic negative single strand RNA.

4. Late transcription of the negative single strand RNA.

5. Late translation of the negative single strand RNA, production and accumulation of late structural proteins.

6. Assembly and maturation of the nucleocapsid. Budding of nucleocapsid through cell membrane from viral envelope.

Protein synthesis:	(-)ssRNA → mRNA → proteins
Gene Replication:	(-)ssRNA → (+)ssRNA → (-)ssRNA
Enzyme:	RNA polimerases provided or coded by the virus: (-)ssRNA → mRNA, (-)ssRNA → (+)ssRNA, (+)ssRNA → (-)ssRNA

The genome could be unsegmented by various open reading frames (Filoviridae, Paramyxoviridae, and Rhabdoviridae), two ambisense segments (Arenavirus), three segments, occasionally ambisense (Bunyaviridae and Tenuivirus), or six to eight segments (Orthomyxoviridae). The genome size is between 10 to 30kb. Therefore, two subgroups of virus can be distinguished:

-Viruses with unsegmented genomes where the first step of replication is the transcription of the negative strand by RNA polymerase that depends on the viral RNA to form various monocistronic mRNA strands that code individual viral proteins. A positive sense single strand copy is therefore formed to serve as template for the the production of the negative genome. This replication takes place in the cytoplasm.

-Viruses with segmented genomes where replication occurs in the nucleus and RNA polymerase depends on the viral RNA to produce a monocistronic mRNA strand from each segment of the genome. The principal difference between the two types is the location of replication.

Note: Negative sense RNA virus replicate outside the nucleus, in the cytoplasm, except for Orthomyxoviridae.

Species/Infections of other animals

These viruses are able to infect vertebrates (Arenaviridae, Prthomyxoviridae, and Paramyxoviridae), vertebrates and arthropods (Bunyaviridae and Rhabdoviridae), arthopods and plants (Bunyaviridae and Rhabdoviridae), or plants (Tenuivirus). Viruses from this group that are able to infect humans include Marburgo virus, Ebola, measles, mumps, rabies, and influenza.