A satellite is a
subviral agent
Virus classification is the process of naming viruses and placing them into a Alpha taxonomy, taxonomic system similar to the classification systems used for cell (biology), cellular organisms.
Viruses are classified by phenotypic characteristics, ...
that depends on the
coinfection
Coinfection is the simultaneous infection of a host by multiple pathogen species. In virology, coinfection includes simultaneous infection of a single cell by two or more virus particles. An example is the coinfection of liver cells with hepatiti ...
of a host cell with a
helper virus for its replication. Satellites can be divided into two major classes: satellite viruses and satellite nucleic acids.
Satellite
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsk ...
es, which are most commonly associated with plants, are also found in mammals, arthropods, and bacteria. They encode
structural protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respond ...
s to enclose their genetic material, which are therefore distinct from the structural proteins of their helper viruses.
Satellite
nucleic acids, in contrast, do not encode their own structural proteins, but instead are encapsulated by proteins encoded by their helper viruses.
The genomes of satellites range upward from 359 nucleotides in length for satellite tobacco ringspot virus RNA (STobRV).
Most viruses have the capability to use host enzymes or their own replication machinery to independently replicate their own viral RNA. Satellites, in contrast, are completely dependent on a
helper virus for replication. The symbiotic relationship between a satellite and a helper virus to catalyze the replication of a satellite genome is also dependent on the host to provide components like
replicases to carry out replication.
A satellite virus of
mamavirus
Mamavirus is a large and complex virus in the Group I family ''Mimiviridae''. The virus is exceptionally large, and larger than many bacteria. Mamavirus and other mimiviridae belong to nucleocytoplasmic large DNA virus (NCLDVs) family. Mamavirus ...
that inhibits the replication of its host has been termed a
virophage. However, the usage of this term remains controversial due to the lack of fundamental differences between virophages and classical satellite viruses.
History and discovery
The
tobacco necrosis virus was the virus that led to the discovery of the first satellite virus in 1962. Scientists discovered that the first satellite had the components to make its own protein shell. A few years later in 1969, scientists discovered another symbiotic relationship with the tobacco ringspot neopvirus (TobRV) and another satellite virus. The emergence of satellite RNA is said to have come from either the genome of the host or its co-infecting agents, and any vectors leading to transmission.
A satellite virus important to human health that demonstrates the need for co-infection to replicate and infect within a host is the virus that causes
hepatitis D
Hepatitis D is a type of viral hepatitis caused by the hepatitis delta virus (HDV). HDV is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a satellite (a type of subviral agent) because it can propagate only in ...
. Hepatitis D or delta virus (HDV) was discovered in 1977 by
Mario Rizzetto and is differentiated from hepatitis A, B, and C because it requires viral particles from
hepatitis B
Hepatitis B is an infectious disease caused by the '' Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection.
Many people have no symptoms during an initial infection. ...
virus (HBV) to replicate and infect liver cells. HBV provides a surface antigen,
HBsAg
HBsAg (also known as the Australia antigen) is the surface antigen of the hepatitis B virus (HBV). Its presence in blood indicates current hepatitis B infection.
Structure and function
The viral envelope of an enveloped virus has different sur ...
, which is utilized by HDV to create a super-infection resulting in liver failure.
HDV is found all over the globe but is most prevalent in Africa, the Middle East and southern Italy.
Satellite compared to a virus
Classification
The classification of subviral agents is ongoing. The following uses an outline for subviral agents in a 2011 ICTV report.
newer version; does not mention satellites
A lot of the taxa have since been assigned more formal names in 2019, so these are included when possible.
Satellite viruses
Some satellite viruses have been assigned a taxon. The following reflects the results of a 2015 proposal that has since been accepted (Taxoprop 2015.009a).
*Single-stranded
RNA satellite viruses
**(unassigned to a family)
***''
Albetovirus
''Albetovirus'' is a plant satellite virus genus. As a member of realm '' Riboviria'' without assigned family or order it contains just three species, ''Tobacco albetovirus 1'', ''2'', and ''3'' (alias Satellite tobacco necrosis virus 1, 2, resp ...
'' – ''
Tobacco necrosis satellite virus 1, 2, and C''
***''
Aumaivirus'' – ''
Maize white line mosaic satellite virus
Maize white line mosaic satellite virus (syn. Satellite maize white line mosaic virus, Satellite virus of maize white line mosaic virus, SMWLMV, SV-MWLMV) is a plant satellite virus. It is the only species in genus ''Aumaivirus'', which is a mem ...
''
***''
Papanivirus'' – ''
Panicum mosaic satellite virus''
***''
Virtovirus'' – ''
Tobacco mosaic satellite virus
''Tobacco virtovirus 1'', informally called Tobacco mosaic satellite virus, Satellite tobacco mosaic virus (STMV), or tobacco mosaic satellite virus, is a satellite virus first reported in ''Nicotiana glauca'' from southern California, U.S.. It ...
'', aka Tobacco necrosis satellite virus
**Family ''
Sarthroviridae''
*** ''
Macronovirus'' – ''
Macrobrachium satellite virus 1'' (extra small virus)
** (unnamed genus) – ''
Nilaparvata lugens commensal X virus
''Nilaparvata''Distant WL (1906) ''The fauna of British India, including Ceylon and Burma.'' 3: 503 pp. 47 is a genus of planthoppers in the subfamily Delphacinae and tribe Delphacini Leach, 1815.
Species are widely distributed in the Americas, ...
''
** (unnamed genus) – ''
Chronic bee-paralysis satellite virus
Chronic may refer to:
* Chronic (cannabis), a slang name for high quality marijuana
* Chronic condition, a condition or disease that is persistent or otherwise long-lasting in its effects
* Chronic toxicity, a substance with toxic effects after c ...
''
* Double-stranded
DNA satellite viruses
** Family ''
Lavidaviridae
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for t ...
'' – Virophages
*** ''
Sputnik virophage
''Mimivirus-dependent virus Sputnik'' (from Russian "satellite") is a subviral agent that reproduces in amoeba cells that are already infected by a certain helper virus; Sputnik uses the helper virus's machinery for reproduction and inhibits r ...
''
*** ''
Zamilon virophage
''Mimivirus-dependent virus Zamilon'', or Zamilon, is a virophage, a group of small DNA viruses that infect protists and require a helper virus to replicate; they are a type of satellite virus. Discovered in 2013 in Tunisia, infecting ''Acanthamo ...
''
*** ''
Mavirus virophage
''Mavirus'' is a genus of double stranded DNA virus that can infect the marine phagotrophic flagellate ''Cafeteria roenbergensis'', but only in the presence of the giant ''CroV'' virus (''Cafeteria roenbergensis''). The genus contains only one ...
''
*** ''
Organic Lake virophage''
*Single-stranded
DNA satellite viruses
** Genus ''
Dependoparvovirus
''Dependoparvovirus'' (formerly ''Dependovirus'' or Adeno-associated virus group) is a genus in the subfamily '' Parvovirinae'' of the virus family '' Parvoviridae''; they are Group II viruses according to the Baltimore classification. Some dep ...
'' –
Adeno-associated virus
Adeno-associated viruses (AAV) are small viruses that infect humans and some other primate species. They belong to the genus ''Dependoparvovirus'', which in turn belongs to the family ''Parvoviridae''. They are small (approximately 26 nm in di ...
group
Satellite nucleic acids
The following may not be comprehensive in its ICTV coverage. The nomenclature for satellite RNAs is to prefix the host virus name with "sat".
Satellite-like nucleic acids resemble satellite nucleic acids, in that they replicate with the aid of helper viruses. However they differ in that they can encode functions that can contribute to the success of their helper viruses; while they are sometimes considered to be genomic elements of their helper viruses, they are not always found within their helper viruses.
*Single-stranded satellite
DNAs
**Family
Alphasatellitidae (encoding a replication initiator protein)
**Family
Tolecusatellitidae[Taxoprop 2016.021a-kP]
*** Genus
Betasatellites (encoding a pathogenicity determinant βC1)
*** Genus
Deltasatellites (appears defective in βC1, but is their own group)
*Double-stranded satellite
RNAs
**''
Saccharomyces cerevisiae M virus satellite''
**''
Trichomonas vaginalis T1 virus satellite''
*Single-stranded satellite RNAs
**Large linear satellite RNAs
***''
Arabis mosaic virus large satellite RNA''
***''
Bamboo mosaic virus satellite RNA'' (satBaMV)
***''
Chicory yellow mottle virus large satellite RNA''
***''
Grapevine Bulgarian latent virus satellite RNA''
***''
Grapevine fanleaf virus satellite RNA''
***''
Myrobalan latent ringspot virus satellite RNA The common name myrobalan can refer to several unrelated fruit-bearing plant species:
* Myrobalan plum (''Prunus cerasifera''), also called cherry plum and myrobalan plum
* Emblic myrobalan (''Phyllanthus emblica''), also called Amla and Amalaki
...
''
***''
Tomato black ring virus satellite RNA''
***''
Beet ringspot virus satellite RNA''
***''
Beet necrotic yellow vein virus RNA5''
**Small linear satellite RNAs
***''
Cucumber mosaic virus satellite RNA''
***''
Cymbidium ringspot virus satellite RNA''
***''
Pea enation mosaic virus satellite RNA''
***''
Groundnut rosette virus satellite RNA''
***''
Panicum mosaic virus small satellite RNA''
***''
Peanut stunt virus satellite RNA''
***''
Turnip crinkle virus satellite RNA''
***''
Tomato bushy stunt virus satellite RNA, B10''
***''
Tomato bushy stunt virus satellite RNA, B1''
***''
Tobacco bushy top virus satellite RNA
Tobacco is the common name of several plants in the genus ''Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the chie ...
''
**Circular satellite RNAs or "
virusoids"
***''
Arabis mosaic virus small satellite RNA''
***''
Tobacco ringspot virus satellite RNA'' (satTRsV) above two forms a clade
***''
Chicory yellow mottle virus satellite RNA'' (satCYMoV)
***''
Solanum nodiflorum mottle virus satellite RNA''
***''
Subterranean clover mottle virus satellite RNA''
***''
Velvet tobacco mottle virus satellite RNA'' above four forms a clade
***''
Lucerne transient streak virus satellite RNA'' (satLTSV)
***''
Cereal yellow dwarf virus-RPV satellite RNA''
***''
Cherry small circular viroid-like RNA''
** Realm ''
Ribozyviria
''Ribozyviria'' is a realm of satellite nucleic acids. Established in ICTV TaxoProp 2020.012D, the realm is named after the presence of genomic and antigenomic ribozymes of the ''Deltavirus'' type. Additional common features include a rod-like s ...
'' / Family ''
Kolmioviridae'' – ''Deltavirus''-like satellite-like RNAs
*** Genus ''
Deltavirus
Hepatitis D is a type of viral hepatitis caused by the hepatitis delta virus (HDV). HDV is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a satellite (a type of subviral agent) because it can propagate only in ...
'' –
Hepadnavirus-associated satellite-like RNAs
**
Polerovirus-associated RNAs
See also
*
Virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsk ...
*
Virusoid
*
Viroid
Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms (flowering plants), and most cause diseases, whose respective economi ...
*
Virophage
*
WikiSpecies:Virus
References
External links
ICTV
{{DEFAULTSORT:Satellite (Biology)
Virology