RNA virus

(noun)

Any of many viruses that possess ribonucleic acid as their genetic material and do not replicate using DNA.

Related Terms

Examples of RNA virus in the following topics:

  • Positive-Strand RNA Viruses of Animals

    • As such, purified RNA of a positive-sense virus can directly cause infection though it may be less infectious than the whole virus particle.
    • Purified RNA of a negative-sense virus is not infectious by itself as it needs to be transcribed into positive-sense RNA; each virion can be transcribed to several positive-sense RNAs.
    • A picornavirus is a virus belonging to the family Picornaviridae.
    • The name is derived from pico, meaning small, and RNA, referring to the ribonucleic acid genome, so "picornavirus" literally means small RNA virus.
    • Foot and Mouth Disease is caused by the Aphthovirus virus which positive-strand RNA virus, of the Picornaviridae family of animal viruses.

  • Viral Genomes

    • The viral genome is the complete genetic complement contained in a DNA or RNA molecule in a virus.
    • A virus has either DNA or RNA genes and is called a DNA virus or a RNA virus, respectively.
    • The vast majority of viruses have RNA genomes.
    • However, all segments are not required to be in the same virion for the virus to be infectious, as demonstrated by the brome mosaic virus and several other plant viruses.
    • The virus particles of some virus families, such as those belonging to the Hepadnaviridae, contain a genome that is partially double-stranded and partially single-stranded.

  • Viral Replication and Gene Expression

    • Viruses that replicate via RNA intermediates need an RNA-dependent RNA-polymerase to replicate their RNA, but animal cells do not seem to possess a suitable enzyme.
    • Therefore, this type of animal RNA virus needs to code for an RNA-dependent RNA polymerase.
    • No viral proteins can be made until viral messenger RNA is available; thus, the nature of the RNA in the virion affects the strategy of the virus: In plus-stranded RNA viruses, the virion (genomic) RNA is the same sense as mRNA and so functions as mRNA.
    • One of these includes RNA-dependent RNA polymerase (RNA replicase), which copies the viral RNA to form a double-stranded replicative form, in turn this directs the formation of new virions.
    • Uncoating of the viral RNA is mediated by receptor-dependent destabilization of the virus capsid (2).

  • Defective Viruses

    • The hepatitis delta virus of humans has an RNA genome similar to viroids, but has a protein coat derived from hepatitis B virus and cannot produce one of its own.
    • Therefore, it is a defective virus and cannot replicate without the help of hepatitis B virus.
    • The hepatitis delta virus of humans has an RNA genome similar to viroids, but has a protein coat derived from hepatitis B virus and cannot produce one of its own.
    • Therefore, it is a defective virus and cannot replicate without the help of hepatitis B virus.
    • Hepatitis D, also referred to as hepatitis D virus (HDV) and classified as Hepatitis delta virus, is a disease caused by a small circular enveloped RNA virus.

  • RNA Oncogenic Viruses

    • Specifically, RNA viruses have RNA as their genetic material and can be either single-stranded RNA (ssRNA) or double-stranded (dsRNA).
    • Since RNA makes up the genome of the mature virus particle, it must be copied to DNA prior to integration into the host cell chromosome.
    • There are two molecules of genomic RNA per virus particle with a 5' cap and a 3' poly A sequence.
    • Thus, the virus is diploid.
    • The RNA is plus sense (same sense as mRNA).

  • Double-Stranded RNA Viruses: Retroviruses

    • A retrovirus is an RNA virus that is duplicated in a host cell using the reverse transcriptase enzyme to produce DNA from its RNA genome.
    • The virus thereafter replicates as part of the host cell's DNA.
    • The virus itself stores its nucleic acid in the form of an mRNA genome and serves as a means of delivering that genome into cells it targets as an obligate parasite (a parasite that cannot live without its host).
    • In most viruses, DNA is transcribed into RNA, and then RNA is translated into protein.
    • A notable retrovirus is Human immunodeficiency virus (HIV), the virus responsible for acquired immunodeficiency syndrome (AIDS).

  • Virus Classification

    • The most commonly-used classification method today is called the Baltimore classification scheme which is based on how messenger RNA (mRNA) is generated in each particular type of virus.
    • The virus core contains the genome or total genetic content of the virus.
    • Viruses can contain double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), double-stranded RNA (dsRNA), single-stranded RNA with a positive polarity (ssRNA), ssRNA with a negative polarity, diploid (two copies) ssRNA, and partial dsDNA genomes.
    • (a) Rabies virus has a single-stranded RNA (ssRNA) core and an enveloped helical capsid, whereas (b) variola virus, the causative agent of smallpox, has a double-stranded DNA (dsDNA) core and a complex capsid.
    • The scheme groups viruses according to how the mRNA is produced during the replicative cycle of the virus, in addition to the differences in morphology and genetics.

  • Viral Identification

    • The genetic material within virus particles varies considerably between different types of viruses.
    • Pararetroviruses do not, although integrated genome copies, usually of plant pararetroviruses, can give rise to infectious virus.
    • Examples of the second type are the Hepadnaviridae, which includes Hepatitis B virus.
    • The Baltimore classification developed by David Baltimore is a virus classification system that groups viruses into families, depending on their type of genome (DNA, RNA, single-stranded (ss), double-stranded (ds), etc.) and their method of replication.
    • An example of Baltimore Virus classification I: dsDNA virusesII: ssDNA virusesIII: dsRNA virusesIV: (+)ssRNA virusesV: (−)ssRNA virusesVI: ssRNA-RT virusesVII: dsDNA-RT viruses

  • Negative-Strand RNA Viruses of Animals

    • Animal RNA viruses can be classified according to the sense or polarity of their RNA into negative-sense, positive-sense, or ambisense RNA viruses.
    • The RNA found in a negative-sense virus is not infectious by itself, as it needs to be transcribed into positive-sense RNA.
    • This RNA negative-strand to positive-strand copying is carried out by an RNA-dependent RNA-polymerase.
    • This virus family includes pathogens—the rabies virus, vesicular stomatitis virus, potato yellow dwarf virus, etc.
    • Paramyxoviruses cause a range of diseases in animal species: canine distemper virus (dogs), phocine distemper virus (seals), cetacean morbillivirus (dolphins and porpoises), Newcastle disease virus (birds), and rinderpest virus (cattle).

  • Replicative Cycle of Influenza A

    • Influenza A follows the typical life cycle of most influenza virus: infection and replication are a multi-step process.
    • After the hemagglutinin is cleaved by a protease, the cell imports the virus by endocytosis.
    • The M2 ion channel allows protons to move through the viral envelope and acidify the core of the virus, which causes the core to dissemble and release the viral RNA and core proteins.
    • The viral RNA (vRNA) molecules, accessory proteins, and RNA-dependent RNA polymerase are then released into the cytoplasm (Step 2 in figure).
    • Host invasion and replication cycle of an influenza virus.