Negative-sense single-stranded RNA virus

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

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Memo:

http://es.wikipedia.org/wiki/Virus_ARN_monocatenario_positivo http://es.wikipedia.org/wiki/Virus_ARN_monocatenario_negativo

http://en.wikipedia.org/wiki/Sense_(molecular_biology)#Positive-sense http://en.wikipedia.org/wiki/RNA_virus#Single-stranded_RNA_viruses_and_RNA_Sense

~500 words; translate + add info? Or translate both (~1k words)

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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 . 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.

Replication

Negative sense RNA virus use a RNA polymerase or transcriptase(?) to form a positive sense RNA. This signifies that the virus must support the RNA polymerase enzyme, which is dependent on the RNA. The 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 new virions, similar to capsid proteins and RNA replicase, which are in charge of the production of new negative sense RNA molecules.

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

Replication of the virus consists of the following steps:

1. Early transcription of negative sense RNA by RNA polymerase depends 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.

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

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.

Works Cited