Since cells do not produce double-stranded RNA during normal nucleic acid metabolism, natural selection has favored the evolution of enzymes that destroy dsRNA on contact. The best known class of this type of enzymes is Dicer. It is hoped that broad-spectrum anti-virals could be synthesized that take advantage of this vulnerability of double-stranded RNA viruses.
Anti-virals
Double-stranded RNA viruses
Double-stranded RNA viruses | Anti-virals
Dicer Since cells do not produce double-stranded RNA during normal nucleic acid metabolism, natural selection has favored the evolution of enzymes that destroy dsRNA on contact. The enzyme 'Dicer'. It is hoped that broad-spectrum anti-virals could be synthesized that take advantage of destruction of double-stranded RNA viruses by the use of Dicer.
rna consists of how many chains of subunits
user
Small RNAs mainly include 5.8S ribosomal RNA (rRNA), 5S rRNA, transfer RNA (tRNA), microRNA (miRNA), small interfering RNA (siRNA), small nucleolar RNA (snoRNAs), Piwi-interacting RNA (piRNA), tRNA-derived small RNA (tsRNA) and small rDNA-derived RNA (srRNA)
assistant
are they also double-stranded?
user
Yes, Double-stranded RNA is RNA with two complementary strands
assistant
how is it different from dna?
user
Analysis of mRNA, tRNA, rRNA, snRNAs, and other non-coding RNAs  has revealed that self-complementary sequences that allow parts of the RNA to fold and pair with itself to form double helices and they are highly structured. Unlike DNA, their structures do not consist of long double helices, but rather collections of short helices packed together into structures akin to proteins
assistant
what is the function of the non-coding ones?
user
Silencing of blocks of chromatin via recruitment of Polycomb complex so that messenger RNA could not be transcribed from them
assistant
who discovered it?
user
Friedrich Miescher
assistant
what is its role in alzheimer?
user
Sorry. I cannot find the answer based on the context.
assistant
what is its double-stranded virus classified into?
user
The phylum "Duplornaviricota" and the class "Duplopiviricetes", which is in the phylum "Pisuviricota"
assistant
what is anti-viral in it?
user
The class "Duplopiviricetes" is the second clade of dsRNA viruses and is in the phylum "Pisuviricota", which also contains positive-sense single-stranded RNA viruses. "Duplopiviricetes" mostly contains plant and fungal viruses and includes the following four families: "Amalgaviridae", "Hypoviridae", "Partitiviridae", and "Picobirnaviridae".
Double-stranded RNA viruses | "Duplopiviricetes"
Duplornaviricota is a phylum of RNA viruses, which contains all double-stranded RNA viruses, except for those in phylum "Pisuviricota." Characteristic of the group is a viral capsid composed of 60 homo- or heterodimers of capsid protein on a pseudo-T=2 lattice. Duplornaviruses infect both prokaryotes and eukaryotes. The name of the group derives from Italian "duplo" which means double (a reference to double-stranded), "rna" for the type of virus, and -"viricota" which is the suffix for a virus phylum.
Duplornaviricota | Introduction
"Duplornaviricota" contains most dsRNA viruses, including reoviruses, which infect a diverse range of eukaryotes, and cystoviruses, which are the only dsRNA viruses known to infect prokaryotes. Apart from RdRp, viruses in "Duplornaviricota" also share icosahedral capsids that contain 60 homo- or heterodimers of the capsid protein organized on a pseudo T=2 lattice. The phylum is divided into three classes: "Chrymotiviricetes", which primarily contains fungal and protozoan viruses, "Resentoviricetes", which contains reoviruses, and "Vidaverviricetes", which contains cystoviruses.
Double-stranded RNA viruses | "Duplornaviricota"
Double-stranded RNA viruses (dsRNA viruses) are a polyphyletic group of viruses that have double-stranded genomes made of ribonucleic acid. The double-stranded genome is used to transcribe a positive-strand RNA by the viral RNA-dependent RNA polymerase (RdRp). The positive-strand RNA may be used as messenger RNA (mRNA) which can be translated into viral proteins by the host cell's ribosomes. The positive-strand RNA can also be replicated by the RdRp to create a new double-stranded viral genome. Double-stranded RNA viruses are classified in two separate phyla "Duplornaviricota" and "Pisuviricota" (specifically class "Duplopiviricetes"), which are in the kingdom "Orthornavirae" and realm "Riboviria". The two groups do not share a common dsRNA virus ancestor.
Double-stranded RNA viruses | Introduction
Pisuviricota is a phylum of RNA viruses, which includes all positive-strand and double-stranded RNA viruses, which infect eukaryotes and are not members of the phylum "Kitrinoviricota," "Lenarviricota," or "Duplornaviricota." The name of the group is a portmanteau of “"pi"cornavirus "su"pergroup” and -"viricota" which is the suffix for a virus phylum. Phylogenetic analyses suggest that "Birnaviridae" and "Permutotetraviridae", both currently unassigned to a phylum in "Orthornavirae", also belong to this phylum and that both are sister groups.
Pisuviricota | Introduction
Durnavirales is an order of double-stranded RNA viruses which infect eukaryotes. The name of the group derives from Italian "duplo" which means double (a reference to double-stranded), "rna" for the type of virus, and -"virales" which is the suffix for a virus order.
Durnavirales | Introduction
Since cells do not produce double-stranded RNA during normal nucleic acid metabolism, natural selection has favored the evolution of enzymes that destroy dsRNA on contact. The best known class of this type of enzymes is Dicer. It is hoped that broad-spectrum anti-virals could be synthesized that take advantage of this vulnerability of double-stranded RNA viruses.
Double-stranded RNA viruses | Anti-virals
Two clades of dsRNA viruses exist: the phylum "Duplornaviricota" and the class "Duplopiviricetes", which is in the phylum "Pisuviricota". Both are included in the kingdom "Orthornavirae" in the realm "Riboviria". Based on phylogenetic analysis of RdRp, the two clades do not share a common dsRNA ancestor but are instead separately descended from different positive-sense, single-stranded RNA viruses. In the Baltimore classification system, which groups viruses together based on their manner of mRNA synthesis, dsRNA viruses are group III.
Double-stranded RNA viruses | Classification
Ghabrivirales is an order of double-stranded RNA viruses. It is the only order in the class Chrysmotiviricetes. The name of the order derives from Said "Ghabri"al, a pioneering researcher who studied viruses in this order, and -"virales" which is the suffix for a virus order. The name of the class is a portmanteau of member viruses ("chrys"ovirus, "m"egabirnavirus, and "toti"virus), and -"viricetes" which is the suffix for a virus class.
Ghabrivirales | Introduction
RHBV is a single stranded, negative-sense RNA virus of the genus "Tenuivirus", derived from the Latin ""tenui"", meaning thin or weak. This comes from the nature of "Tenuiviruses" to form thin, filamentous viral particles. Other viruses in the genus "Tenuivirus" include maize stripe virus (MSV), rice stripe virus (RSV), and rice grassy stunt virus (RGSV). While RHBV and other "Tenuiviruses" have single stranded RNA genomes, it is interesting to note that examination of non-denaturing gel electrophoresis performed with "Tenuiviruses" has yielded both single stranded and double stranded RNA. Because it is unlikely that both single stranded and double stranded RNA's are encapsidated within the viral ribonucleoprotein, it is theorized that the double stranded RNA sometimes present in gel electrophoresis results comes from the annealing in vitro of single stranded RNA's that possess opposite polarities.
Rice hoja blanca tenuivirus | Viral Classification
With the exception of the Hepatitis D virus, this group of viruses has been placed into a single phylum—Negarnaviricota. This phylum has been divided into two subphyla—Haploviricotina and Polyploviricotina. Within the subphylum Haploviricotina four classes are currently recognised: Chunqiuviricetes, Milneviricetes, Monjiviricetes and Yunchangviricetes. In the subphylum Polyploviricotina two classes are recognised: Ellioviricetes and Insthoviricetes. Six classes, seven orders and twenty four families are currently recognised in this group. A number of unassigned species and genera are yet to be classified.
RNA virus | Group V – negative-sense ssRNA viruses
Moreover, the structural and functional similarities with dsRNA viruses of mammals has made it useful to consider these entities as viruses.
Double-stranded RNA viruses | "Saccharomyces cerevisiae" virus L-A
The third phylum that contains +ssRNA viruses is "Pisuviricota", which has been informally called the "picornavirus supergroup". The phylum contains a large assemblage of eukaryotic viruses known to infect animals, plants, fungi, and protists. The phylum contains three classes, two of which contain only +ssRNA viruses: "Pisoniviricetes", which contains nidoviruses, picornaviruses, and sobeliviruses, and "Stelpaviricetes", which contains potyviruses and astroviruses. The third class is "Duplopiviricetes", whose members are double-stranded RNA viruses that are descended from +ssRNA viruses.
Positive-strand RNA virus | "Pisuviricota"
"Negarnaviricota" is divided into two subphyla: "Haploviricotina", whose members synthesize a cap structure on viral mRNA required for protein synthesis, and "Polyploviricotina", whose members instead obtain caps on mRNA via cap snatching.
Baltimore classification | Group V: negative sense single-stranded RNA viruses
The genome of viruses from this family is unsegmented, -RT, positive-sense, single-stranded RNA and is 4200–9700 nucleotides long. The genome encodes structural proteins and non-structural proteins which codes for an RNA-dependent DNA polymerase, replicase, and reverse transcriptase for the reverse transcription step during replication.
Pseudoviridae | Genome
This small group of viruses, exemplified by the Hepatitis B virus, have a double-stranded, gapped genome that is subsequently filled in to form a covalently closed circle (cccDNA) that serves as a template for production of viral mRNAs and a subgenomic RNA. The pregenome RNA serves as template for the viral reverse transcriptase and for production of the DNA genome.
Viral replication | Class 7: Double-stranded DNA viruses that replicate through a single-stranded RNA intermediate
The "Pithoviridae" have only two known representatives. These viruses infects amoebas and can survive in low temperatures. For years this virus was believed to be frozen, but due to climate change it has begun to show up again. This is a double stranded DNA virus with its size being 610 kilobases long. The genome is estimated to code for 476 open reading frames. The viron is rod shaped with a length of 1,100 nm long and 500 nm in diameter.
Nucleocytoviricota | "Pithoviridae"
"Negarnaviricota" takes the first part of its name from Latin "nega", meaning negative, the middle part "rna" refers to RNA, and the final part, -"viricota", is the suffix used for virus phyla. The subphylum "Haploviricotina" takes the first part of its name, "Haplo", from Ancient Greek ἁπλός, meaning simple, and -"viricotina" is the suffix used for virus subphyla. The subphylum "Polyploviricotina" follows the same pattern, "Polyplo" being taken from Ancient Greek πολύπλοκος, meaning complex.
Negative-strand RNA virus | Etymology
The viral RNA molecules of some members of this genus contain four hair-pin structures and a pseudoknot in the 3'UTR. These secondary structures have been found to be important in viral RNA replication.
Closterovirus | RNA pseudoknot
Stelpaviricetes is a class of non-enveloped, positive-strand RNA viruses which infect plants and animals. Characteristic of the group is a VPg protein attached to the 5'-end of the genome and a conserved 3C-like protease from the PA clan of proteases for processing the translated polyprotein. The name of the group is a portmanteau of member orders ""stel"lavirales, "pa"tatavirales" and -"viricetes" which is the suffix for a virus class.
Stelpaviricetes | Introduction
Pisoniviricetes is a class of positive-strand RNA viruses which infect eukaryotes. A characteristic of the group is a conserved 3C or 3C-like protease from the PA clan of proteases for processing the translated polyprotein. The name of the group is a portmanteau of member orders ""pi"cornavirales, "so"belivirales, "ni"dovirales" and -"viricetes" which is the suffix for a virus class.
Pisoniviricetes | Introduction
Revtraviricetes is a class of viruses that contains all viruses that encode a reverse transcriptase. The group includes all ssRNA-RT and dsDNA-RT viruses. It is the sole class in the phylum Artverviricota, which is the sole phylum in the kingdom Pararnavirae. The name of the group is a portmanteau of ""rev"erse "tra"nscriptase" and -"viricetes" which is the suffix for a virus class.
Revtraviricetes | Introduction
In the nucleus the single-stranded virus genome is converted to dsDNA by a cell DNA polymerase. The ends of the genome are double stranded as a result of base pairing, and at the 3' end the terminal nucleotides act as a primer to which the polymerase binds.
Parvoviridae | Single-stranded DNA to double-stranded DNA
An exception to this viewpoint is that encapsulins have also been identified in archaea of the phylum Crenarchaeota, which are not known to be infected by tailed bacteriophages, so the relation between encapsulins and "Duplodnaviria" remains unresolved. The ATPase subunit of "Duplodnaviria" terminases that generates energy for packaging viral DNA has the same general structural design of the P-loop fold as the packaging ATPases of double jelly roll viruses in the realm "Varidnaviria" but are otherwise not directly related to each other. While viruses in "Duplodnaviria" make use of the HK97 fold for their major capsid proteins, the major capsid proteins of viruses in "Varidnaviria" instead are marked by vertical single or double jelly roll folds.
Duplodnaviria | Phylogenetics
The "Phycodnaviridae" are icosahedral in shape with a double-stranded DNA molecule. Some members of this family can have a linear double stranded DNA while others have a circular double stranded DNA. The genome has been found to be up to 560 kilobases in length. Up to 50% of the DNA can be represented by guanine or cytosine. This virus is known to infect algae, which means it is found in the ocean.
Nucleocytoviricota | "Phycodnaviridae"
Like most viruses with RNA genomes, double-stranded RNA viruses do not rely on host polymerases for replication to the extent that viruses with DNA genomes do. Double-stranded RNA viruses are not as well-studied as other classes. This class includes two major families, the Reoviridae and Birnaviridae. Replication is monocistronic and includes individual, segmented genomes, meaning that each of the genes codes for only one protein, unlike other viruses, which exhibit more complex translation.
Viral replication | Class 3: Double-stranded RNA viruses
The third Baltimore group contains viruses that have a double-stranded RNA (dsRNA) genome. After entering a host cell, the dsRNA genome is transcribed to mRNA from the negative strand by the viral RNA-dependent RNA polymerase (RdRp). The mRNA may be used for translation or replication. Single-stranded mRNA is replicated to form the dsRNA genome. The 5'-end of the genome may be naked, capped, or covalently bound to a viral protein. dsRNA is not a molecule made by cells, so cellular life has evolved antiviral systems to detect and inactivate viral dsRNA. To counteract this, many dsRNA genomes are constructed inside of capsids, thereby avoiding detection inside of the host cell's cytoplasm.
Baltimore classification | Group III: double-stranded RNA viruses
Phenuiviridae is a virus family belonging to the order "Bunyavirales" established in 2016. Ruminants, camels, humans, and mosquitoes are the known hosts of members of this negative-sense single-stranded RNA virus family. Of the genera, "Phlebovirus" is the only genus that includes viruses that cause disease in humans (e.g. Rift Valley Fever Phlebovirus).
Phenuiviridae | Introduction
"Avian metaavulavirus 2" is a negative sense RNA virus with a monopartite genome. It belongs to of the Baltimore Classification System of viruses.
Avian metaavulavirus 2 | Viral classification
"Bacilloviridae" are a suggested family of double stranded DNA viruses that infect species belonging to the archaeal genera "Sulfolobus" and "Thermoproteus".
Bacilloviridae | Introduction
The hemagglutinin (H) and neuraminidase (N) proteins are targets for antiviral drugs. These proteins are also recognised by antibodies, i.e. they are antigens. The responses of antibodies to these proteins are used to classify the different serotypes of influenza A viruses, hence the "H" and "N" in "H5N1". The genome sequence has terminal repeated sequences; repeated at both ends. Terminal repeats at the 5′-end 12–13 nucleotides long. Nucleotide sequences of 3′-terminus identical; the same in genera of same family; most on RNA (segments), or on all RNA species. Terminal repeats at the 3′-end 9–11 nucleotides long. Encapsidated nucleic acid is solely genomic.
Orthomyxoviridae | Genome
Ligamenvirales is an order of linear viruses that infect archaea of the kingdom Crenarchaeota and have double-stranded DNA genomes. The order was proposed by David Prangishvili and Mart Krupovic in 2012 and subsequently created by the International Committee on Taxonomy of Viruses (ICTV). The name is derived from the Latin , meaning "string" or "thread".
Ligamenvirales | Introduction
"Negarnaviricota" belongs to the kingdom "Orthornavirae", which encompasses all RNA viruses that encode RdRp, and the realm "Riboviria", which includes "Orthornavirae" as well as all viruses that encode reverse transcriptase in the kingdom "Pararnavirae". "Negarnaviricota" contains two subphyla, which contain a combined six classes, five of which are monotypic down to lower taxa: Negative-strand RNA viruses are classified as Group V in the Baltimore classification system, which groups viruses together based on their manner of mRNA production and which is often used alongside standard virus taxonomy, which is based on evolutionary history. Therefore, Group V and "Negarnaviricota" are synonymous.
Negative-strand RNA virus | Classification
This analysis also suggests that the dsRNA viruses are not closely related to each other but instead belong to four additional classes—Birnaviridae, Cystoviridae, Partitiviridae, and Reoviridae—and one additional order (Totiviridae) of one of the classes of positive ssRNA viruses in the same subphylum as the positive-strand RNA viruses. One study has suggested that there are two large clades: One includes the families "Caliciviridae", "Flaviviridae", and "Picornaviridae" and a second that includes the families "Alphatetraviridae", "Birnaviridae", "Cystoviridae", Nodaviridae", and "Permutotretraviridae".
RNA virus | Double-stranded RNA viruses
Antiviral proteins are proteins that are induced by human or animal cells to interfere with viral replication. These proteins are isolated to inhibit the virus from replicating in a host's cells and stop it from spreading to other cells. The Pokeweed antiviral protein and the Zinc-Finger antiviral protein are two major antiviral proteins that have undergone several tests for viruses, including HIV and influenza.
Antiviral protein | Introduction
Chrysoviridae is a family of double-stranded RNA viruses. Members of the family are called chrysoviruses.
Chrysoviridae | Introduction
All viruses in "Negarnaviricota" are negative-sense, single-stranded RNA (-ssRNA) viruses. They have genomes made of RNA, which are single instead of double-stranded. Their genomes are negative sense, meaning that messenger RNA (mRNA) can be synthesized directly from the genome by the viral enzyme RNA-dependent RNA polymerase (RdRp), also called RNA replicase, which is encoded by all -ssRNA viruses. Excluding viruses in the genus "Tenuivirus" and some in the family "Chuviridae", all -ssRNA viruses have linear rather than circular genomes, and the genomes may be segmented or non-segmented. All -ssRNA genomes contain terminal inverted repeats, which are palindromic nucleotide sequences at each end of the genome.
Negative-strand RNA virus | Genome
Quadriviridae is a family of double-stranded RNA viruses with a single genus Quadrivirus. The fungi "Rosellinia necatrix" serves as a natural host. The name of the group derives from the "quadri"partite genome of its members where in Latin "quad" means four. There is currently only one species in this family: the type species "Rosellinia necatrix quadrivirus 1".
Quadriviridae | Introduction
Thus the sequence of scAAV is likely unwound by a virally encoded DNA helicase before being packaged into viral protein capsid.
Self-complementary adeno-associated virus | Viral packaging
"Pseudoviridae" is unofficially classified under group VI RNA Reverse Transcribing Viruses and infect fungi and invertebrates. "Pseudoviridae" comprises highly divergent members and most "Pseudoviridae" encode Gag and Pol on a single open reading frame. "Pseudoviridae" is included in the order "Ortervirales" along with families "Belpaoviridae", "Metaviridae", "Retroviridae", and "Caulimoviridae".
Pseudoviridae | Taxonomy
The host cell's RNA polymerase II then transcribes RNA in the nucleus from the proviral DNA. Some of this RNA may become mRNA whereas other strands will become copies of the viral genome for replication. ssRNA-RT viruses are all included in the class "Revtraviricetes", phylum "Arterviricota", kingdom "Pararnavirae" of the realm "Riboviria". Excluding "Caulimoviridae", which belongs to Group VII, all members of the "Revtraviricetes" order "Ortervirales" are ssRNA-RT viruses.
Baltimore classification | Group VI: single-stranded RNA viruses with a DNA intermediate
The majority of fungal viruses are double-stranded RNA viruses. A small number of positive-strand RNA viruses have been described. One report has suggested the possibility of a negative stranded virus.
RNA virus | Notes
Caulimoviridae is a family of viruses infecting plants. There are currently 85 species in this family, divided among 10 genera. Viruses belonging to the family "Caulimoviridae" are termed double-stranded DNA (dsDNA) reverse-transcribing viruses (or pararetroviruses) i.e. viruses that contain a reverse transcription stage in their replication cycle. This family contains all plant viruses with a dsDNA genome that have a reverse transcribing phase in its lifecycle.
Caulimoviridae | Introduction
Viruses in "Picovirinae" are non-enveloped, with icosahedral or prolate heads of about 50–55 nm in diameter, and short tails. Genomes are linear, double stranded DNA, and are relatively small (between 16–20 kbp)-hence the term pico-virinae. Picoviruses package linear, monomeric genomes with a terminal protein covalently attached to each end.
Picovirinae | Structure
Siphoviridae is a family of double-stranded DNA viruses in the order "Caudovirales". Bacteria and archaea serve as natural hosts. There are currently 783 species in this family, divided among 265 genera and 13 subfamilies. The characteristic structural features of this family are a nonenveloped head and noncontractile tail.
Siphoviridae | Introduction
mRNA is forced out from the capsid in order to be translated or to be translocated from a mature capsid to a progeny capsid. While dsRNA viruses typically have capsids, viruses in the families "Amalgaviridae" and "Endornaviridae" have not been observed to form virions and as such apparently lack capsids. Endornaviruses are also unusual in that unlike other RNA viruses, they possess a single, long open reading frame (ORF), or translatable portion, and a site-specific nick in the 5' region of the positive strand. dsRNA viruses are classified into two phyla within the kingdom "Orthornavirae" of the realm "Riboviria":
Baltimore classification | Group III: double-stranded RNA viruses
Ortervirales is an order that contains all accepted species of single-stranded RNA viruses that replicate through a DNA intermediate (Group VI) and all accepted species of double-stranded DNA viruses (except "Hepadnaviridae") that replicate through an RNA intermediate (Group VII). All reverse-transcribing viruses possess significant similarities to each other. Their reverse transcriptase proteins share a common origin. Moreover, belpaoviruses, metaviruses, pseudoviruses, and retroviruses have other features in common. Their polymerase proteins are similar in structure and include aspartic protease (retroviral aspartyl protease) and an integrase belonging to the DDE recombinase superfamily (see Recombination-activating gene [structure]). They also share similar capsid and nucleocapsid proteins/domains.
Ortervirales | Introduction
Alsuviricetes is a class of RNA viruses which infect eukaryotes. Member viruses have a positive-sense single-stranded RNA genome. The name of the group is a portmanteau of ""al"pha "su"pergroup" and -"viricetes" which is the suffix for a virus class.
Alsuviricetes | Introduction
The viruses in this family are non occluded, enveloped, rod-shaped virions measuring 500–1,000 nanometers (nm) in length and 50–80 nm in diameter . The virions contain a thin, dense central nucleocapsid that encases the DNA-protein core. The nucleocapsid core is surrounded by an amorphous proteinaceous tegument layer. The outer surface of the virions is studded with helical polymeric structure composed of virally-encoded and host-derived protein dimers. The virions contain at least 35 polypeptides which range in size from 10 to 200 kiloDaltons. The genome is a supercoiled, circular double stranded DNA (dsDNA) molecule ranging in size from 120 to 190 kilobases with 108-174 putative non-overlapping genes that are equally distributed over the genome in unidirectional clusters.
Hytrosaviridae | Description
This is the Poxvirus family, which comprises highly pathogenic viruses that infect vertebrates.
Viral replication | Class 1: Double-stranded DNA viruses
All viruses in this family possess a nonsegmented, polyadenylated, positive-sense, single-strand RNA genome around 7.5–8.5 kilobases in length, enclosed in an icosahedral capsid of 27–40 nanometers in diameter.
Caliciviridae | Virology
Some viruses replicate within archaea: these are double-stranded DNA viruses with unusual and sometimes unique shapes. These viruses have been studied in most detail in the thermophilic archaea, particularly the orders Sulfolobales and Thermoproteales. Defences against these viruses involve RNA interference from repetitive DNA sequences within archaean genomes that are related to the genes of the viruses. Most archaea have CRISPR–Cas systems as an adaptive defence against viruses. These enable archaea to retain sections of viral DNA, which are then used to target and eliminate subsequent infections by the virus using a process similar to RNA interference.
Virus | Archaeal viruses
Because EHDV is a double-stranded RNA virus, it needs to overcome a specific set of problems, the main one being the fact that double-stranded RNA is unable to be used as template strand during mRNA translation using host cell machinery. Therefore, EHDV must bring its own transcription enzymes into the cell, to survive and synthesize viral RNA and proteins. However, antiviral defense mechanisms are able to easily recognize and eliminate naked double-stranded RNA in the cell. The presence of the double-stranded RNA would trigger antiviral mechanisms such as apoptosis and interferon production. In order to bypass these host defenses, double-stranded RNA viruses such as EHDV “hide” their genome and other translation machinery within closed protein capsids.
Epizootic hemorrhagic disease virus | Replication and transmission
She also studies antivirals that work through mechanisms other than reverse transcriptase inhibition such as the HIV entry inhibitor maraviroc; she found that genetic variants of CYP3A genes could impact its clearance.
Namandjé Bumpus | Research
Viruses in Virgaviridae are non-enveloped, with rigid helical rod geometries, and helical symmetry. The diameter is around 20-25 nm, and virions have a central "canal." Genomes are linear, single-stranded, positive sense RNA with a 3'-tRNA like structure and no polyA tail. They may be in one, two, or three segments, depending on the genus. Coat proteins are about 19–24 kiloDaltons.
Virgaviridae | Structure
Adolfo García-Sastre, Palese's research showed that most negative-strand RNA viruses counteract antiviral responses in infected hosts, owing to proteins possessing interferon antagonist activity. His work on "fundamental questions concerning the genetic make-up and biology of viruses" and virus-host interactions "uses molecular biological techniques to understand how viruses replicate and how they interact with cells to cause disease in their hosts", with emphasis on "the study of RNA viruses, including influenza, paramyxo and corona (SARS) viruses". Recent achievements include the development of a highly successful new animal model (the guinea pig) for studying the transmission of influenza viruses.
Peter Palese | Biography
Caudovirales is an order of viruses known as the tailed bacteriophages ("cauda" is Latin for "tail"). Under the Baltimore classification scheme, the "Caudovirales" are group I viruses as they have double stranded DNA (dsDNA) genomes, which can be anywhere from 18,000 base pairs to 500,000 base pairs in length. The virus particles have a distinct shape; each virion has an icosahedral head that contains the viral genome, and is attached to a flexible tail by a connector protein. The order encompasses a wide range of viruses, many containing genes of similar nucleotide sequence and function. However, some tailed bacteriophage genomes can vary quite significantly in nucleotide sequence, even among the same genus.
Caudovirales | Introduction
After replication, the dsDNA genome may be packed or sent to the nucleus for further rounds of transcription. dsDNA-RT viruses are, like ssRNA-RT, all included in the class "Revtraviricetes". Two families of dsDNA-RT viruses are recognized: "Caulimoviridae", which belongs to the order "Ortervirales", and "Hepadnaviridae", which is the sole family in the order "Blubervirales".
Baltimore classification | Group VII: double-stranded DNA viruses with an RNA intermediate
The eleven dsRNA strands remain within the protection of the two protein shells and the viral RNA-dependent RNA polymerasecreates mRNA transcripts of the double-stranded viral genome. By remaining in the core, the viral RNA evades innate host immune responses called RNA interference that are triggered by the presence of double-stranded RNA.
Rotaviral gastroenteritis | Replication
All viruses that encode a reverse transcriptase (also known as RT or RNA-dependent DNA polymerase) are members of the class "Revtraviricetes", within the phylum "Arterviricota", kingdom "Pararnavirae", and realm "Riboviria". The class "Blubervirales" contains the single family "Hepadnaviridae" of DNA RT (reverse transcribing) viruses; all other RT viruses are members of the class Ortervirales.
Virus classification | Reverse transcribing viruses
Like other members of the "Reoviridae" family, viruses of the "Sedoreovirinae" subfamily are made of naked, icosahedral capsids containing 10-12 segments of linear double-stranded RNA (dsRNA). The Baltimore System of viral classification categorizes "Reoviridae" in Group III.
Sedoreovirinae | Characteristics
Viruses in the family "Totiviridae" are non-enveloped, double-stranded RNA viruses with icosahedral geometries, and T=2 symmetry. The virion consists of a single capsid protein and is about 40 nanometers in diameter.
Totiviridae | Structure
The negative-sense RNA viruses and indeed all genes defined as negative-sense cannot be directly accessed by host ribosomes to immediately form proteins. Instead, they must be transcribed by viral polymerases into the "readable" complementary positive-sense. These can also be divided into two groups: Examples in this class include the families Orthomyxoviridae, Paramyxoviridae, Bunyaviridae, Filoviridae, and Rhabdoviridae (which includes rabies).
Viral replication | Class 5: Single-stranded RNA viruses - negative-sense
Reverse-transcribing virus is a generic term, which may refer to any member of the families: Families "Retroviridae", "Metaviridae", "Belpaoviridae", "Pseudoviridae", and "Caulimoviridae" are included in the order "Ortervirales".
Reverse transcribing virus | Introduction
Dichorhavirus is a genus of negative sense, single-stranded RNA viruses of plants within the family "Rhabdoviridae". Dichorhaviruses have segmented genomes and their short bacilliform virions are not enveloped. Dichorhaviruses are transmitted by mites.
Dichorhavirus | Introduction
Viruses with a DNA genome, except for the DNA reverse transcribing viruses, are members of three of the four recognized viral realms: "Duplodnaviria", "Monodnaviria", and "Varidnaviria". But the "incertae sedis" order "Ligamenvirales", and many other "incertae sedis" families and genera, are also used to classify DNA viruses. The domains "Duplodnaviria" and "Varidnaviria" consist of double-stranded DNA viruses; other double-stranded DNA viruses are "incertae sedis". The domain "Monodnaviria" consists of single-stranded DNA viruses that generally encode a HUH endonuclease; other single-stranded DNA viruses are "incertae sedis".
Virus classification | DNA viruses
Most viruses produce long dsRNA helices during transcription and replication. In contrast, uninfected mammalian cells generally produce dsRNA helices of fewer than 24 base pairs during transcription. DRACO (double-stranded RNA activated caspase oligomerizer) is a group of experimental antiviral drugs initially developed at the Massachusetts Institute of Technology. In cell culture, DRACO was reported to have broad-spectrum efficacy against many infectious viruses, including dengue flavivirus, Amapari and Tacaribe arenavirus, Guama bunyavirus, H1N1 influenza and rhinovirus, and was additionally found effective against influenza "in vivo" in weanling mice. It was reported to induce rapid apoptosis selectively in virus-infected mammalian cells, while leaving uninfected cells unharmed.
Antiviral drug | Long dsRNA helix targeting
The "Iridoviridae" have linear double stranded DNA genomes up to 220 kilobases long and can code for about 211 proteins. The capsid of this virion is icosahedral shaped and can be up to 350 nm wide. The replication cycle of this virus begins in the nucleus of the host and end in the cytoplasm. Some viruses of this family are often found infecting amphibians while other are found in insect and crustaceans.
Nucleocytoviricota | "Iridoviridae"
Articulavirales is the only order of viruses in the monotypic class Insthoviricetes. The order name "Articulavirales" derives from Latin meaning "segmented" added to the suffix for virus orders "-virales". The class name "Insthoviricetes" is a portmanteau of member viruses ""in"fluenza, i"s"avirus, and "tho"gotovirus" added to the suffix "-viricetes" for virus classes.
Articulavirales | Introduction
Hepadnaviruses have very small genomes of partially double-stranded, partially single stranded circular DNA (pdsDNA). The genome consists of two strands, a longer negative-sense strand and a shorter and positive-sense strand of variable length. In the virion these strands are arranged such that the two ends of the long strand meet but are not covalently bonded together. The shorter strand overlaps this divide and is connected to the longer strand on either side of the split through a direct repeat (DR) segment that pairs the two strands together. In replication, the viral pdsDNA is converted in the host cell nucleus to covalently-closed-circular DNA (cccDNA) by the viral polymerase.
Hepadnaviridae | Genome
Once a virus genome becomes operational in a host cell, it then generates messenger RNA (mRNA) molecules that direct the synthesis of viral proteins. Production of mRNA is initiated by proteins known as transcription factors. Several antivirals are now being designed to block attachment of transcription factors to viral DNA.
Antiviral drug | Transcription
Most viruses in "Varidnaviria" contain a capsid that is made of major capsid proteins that contain vertical single (SJR) or double jelly roll (DJR) folds. The major capsid proteins are named so because they are the primary proteins that the capsid is made of. A jelly roll fold is a type of folded structure in a protein in which eight antiparallel beta strands are organized into four antiparallel beta sheets in a layout resembling a jelly roll, also called a Swiss roll. Each beta strand is a specific sequence of amino acids, and these strands bond to their antiparallel strands via hydrogen bonds.
Varidnaviria | MCP, mCP, and ATPase
Ambisense RNA viruses resemble negative-sense RNA viruses, except they also translate genes from the positive strand.
RNA virus | Single-stranded RNA viruses and RNA Sense
The genome consists of a bi-segmented linear, single-stranded negative sense RNA. The first segment is about 6350–7000 nucleotides in length; the second, about 5630–6500 nucleotides in length.
Varicosavirus | Genome
Viruses in "Dicistroviridae" are non-enveloped, with icosahedral geometries, and T=pseudo3 symmetry. The diameter is around 30 nm. Genomes are linear and non-segmented, around 8.5-10.2kb in length. The genome has 2 open reading frames.
Dicistroviridae | Structure
Abacavir is a nucleoside reverse transcriptase inhibitor that inhibits viral replication. It is a guanosine analogue that is phosphorylated to carbovir triphosphate (CBV-TP). CBV-TP competes with the viral molecules and is incorporated into the viral DNA. Once CBV-TP is integrated into the viral DNA, transcription and HIV reverse transcriptase is inhibited.
Abacavir | Mechanism of action
Although several models have been proposed to account for virus extinction by excess mutations, an extension of the violation of the error threshold stands as a likely mechanism. Interestingly, some antiviral agents licensed for human use, initially thought to act only as inhibitors of viral replication, may actually exert their antviral activity against some RNA viruses at least partially by lethal mutagenesis. This is the case of favipiravir (T-705; 6-fluoro-3-hydroxy-2-pirazinecarboxamide) and ribavirin (1-β-D-ribofuranosyl-1-H-1,2,4-triazole-3-carboxamide) that are currently being intensively investigated as lethal mutagens. Defense mechanisms based on genome modification of invading genetic parasites such as editing cellular activities that are recruited as part of the innate immune response (ADAR, APOBEC, RIP, etc.) represent a natural counterpart of the principle utilized by lethal mutagenesis.
Viral quasispecies | Lethal mutagenesis
The virally encoded RNA polymerase is also found in the interior. By mass, the virion is greater than 50% protein, 20–30% lipid and 2–7% carbohydrate. The density of the virions is 1.18 gram per cubic centimeter. These features are common to all members of the family "Hantaviridae".
Orthohantavirus | Structure
Viruses that fall under this category include ones that are not as well-studied, but still do pertain highly to vertebrates. Two examples include the Circoviridae and Parvoviridae. They replicate within the nucleus, and form a double-stranded DNA intermediate during replication. A human Anellovirus called TTV is included within this classification and is found in almost all humans, infecting them asymptomatically in nearly every major organ.
Viral replication | Class 2: Single-stranded DNA viruses
Kitrinoviricota is a phylum of RNA viruses, which includes all positive-strand RNA viruses, which infect eukaryotes and are not members of the phylum "Pisuviricota" or "Lenarviricota." The name of the group derives from Greek "κίτρινος" ("kítrinos") which means yellow (a reference to yellow fever virus) and -"viricota" which is the suffix for a virus phylum.
Kitrinoviricota | Introduction
The name ""Varidnaviria"" is a portmanteau of "vari"ous "DNA" viruses and the suffix -"viria", which is the suffix used for virus realms. Double-stranded DNA (dsDNA) viruses in the realm are often called non-tailed or tailless dsDNA viruses to distinguish them from the tailed dsDNA viruses of "Duplodnaviria".
Varidnaviria | Etymology
The "Poxviridae" have a linear double-stranded DNA molecule that can have a length of up to 230 kilobases. The replication of these viruses takes place in the cytoplasm. Smallpox, cowpox, and other pox viruses belong to this family.
Nucleocytoviricota | "Poxviridae"
The viruses of this genus have segmented, bipartite genomes that add up to 7,500–19,500 nucleotides in length. Their genomes also code for proteins that do not form part of the virion particles as well as structural proteins. The Universal Virus Database describes that their genome sequences near their 3'-ends are capable of hairpin-loop formation and also believe that their 5'-ends may have methylated caps. Each of the viral RNA molecules contains four hair-pin structures and a pseudoknot in the 3'UTR. The pseudoknot is unusual in that it contains a small stem-loop structure inside loop L1. In the related genus Closterovirus, these secondary structures have been found to be important in viral RNA replication.
Crinivirus | Genetics
It is approximately 7.2 kb in size and encodes a high-molecular-mass protein (L; 200 kDa) and an 11 kDa small polypeptide Z with unknown function and a ring finger motif. The viral RNA-dependent RNA polymerase is encoded by the L protein which contains conserved characteristic motifs throughout all the RNA-dependent, RNA-polymerases. The S strand is ambisense and approximately 3.4 kb in size. It encodes the two main structural proteins: nucleo-protein (63 kDa) and glycoprotein C (75kDa). The latter undergoes posttranslational cleavage and results in the synthesis of two mature virion glycoproteins, GP-1 (40 to 46 kDa) and GP-2 (35 kDa).
Lymphocytic choriomeningitis | Virus biology
The negative-sense, (non-coding) strand is complementary to the viral mRNA. The viral DNA is found in the nucleus soon after infection of the cell. The partially double-stranded DNA is rendered fully double-stranded by completion of the (+) sense strand by cellular DNA polymerases (viral DNA polymerase is used for a later stage) and removal of the viral polymerase protein (P) from the (-) sense strand and a short sequence of RNA from the (+) sense strand. Non-coding bases are removed from the ends of the (-)sense strand and the ends are rejoined. The viral genes are transcribed by the cellular RNA polymerase II in the cell nucleus from a covalently closed circular DNA (cccDNA) template.
Hepatitis B virus | Encoding
RDPV was classified as a separate species due to its unique patterns of restriction enzymes. Parapoxviruses belongs to the family of viruses named "Poxviridae", family of double-stranded DNA viruses. "Parapoxvirus" is classified into the subfamily of "Chordopoxvirinae".
Red deerpox virus | Viral classification
Iridoviridae is a family of viruses with double-stranded DNA genomes. Amphibians, fish, and invertebrates such as arthropods serve as natural hosts. There are currently 19 species in this family, divided among two subfamilies and six genera.
Iridoviridae | Introduction
Double-stranded RNA viruses evolved two separate times from positive-strand RNA viruses. In the Baltimore classification system, dsRNA viruses belong to Group III. Virus group members vary widely in host range (animals, plants, fungi, and bacteria), genome segment number (one to twelve), and virion organization (T-number, capsid layers, or turrets). Double-stranded RNA viruses include the rotaviruses, known globally as a common cause of gastroenteritis in young children, and bluetongue virus, an economically significant pathogen of cattle and sheep. The family "Reoviridae" is the largest and most diverse dsRNA virus family in terms of host range.
Double-stranded RNA viruses | Introduction
Negative-strand RNA viruses constitute the phylum Negarnaviricota, in the kingdom "Orthornavirae" and realm "Riboviria". They are descended from a common ancestor that was a double-stranded RNA (dsRNA) virus, and they are considered to be a sister clade of reoviruses, which are dsRNA viruses. Within the phylum, there are two major branches that form two subphyla: "Haploviricotina", whose members are mostly non-segmented and which encode an RdRp that synthesizes caps on mRNA, and "Polyploviricotina", whose members are segmented and which encode an RdRp that snatches caps from host mRNAs. A total of six classes in the phylum are recognized. Negative-strand RNA viruses are closely associated with arthropods and can be informally divided between those that are reliant on arthropods for transmission and those that are descended from arthropod viruses but can now replicate in vertebrates without the aid of arthropods.
Negative-strand RNA virus | Introduction
"Reoviridae" are currently classified into nine genera. The genomes of these viruses consist of 10 to 12 segments of dsRNA, each generally encoding one protein. The mature virions are non-enveloped. Their capsids, formed by multiple proteins, have icosahedral symmetry and are arranged generally in concentric layers. A distinguishing feature of the dsRNA viruses, irrespective of their family association, is their ability to carry out transcription of the dsRNA segments, under appropriate conditions, within the capsid. In all these viruses, the enzymes required for endogenous transcription are thus part of the virion structure.
Double-stranded RNA viruses | Reoviridae
RNA viruses typically do not encode that many proteins, but most positive-sense, single-stranded (+ssRNA) viruses and some double-stranded RNA (dsRNA) viruses encode a major capsid protein that has a single jelly roll fold, so named because the folded structure of the protein contains a structure that resembles a jelly roll. Many RNA viruses also encode an envelope, a type of lipid membrane that typically surrounds the capsid. In particular, the viral envelope is near-universal among negative-sense, single-stranded (-ssRNA) viruses.
Orthornavirae | Structure
RCN is a double-stranded DNA virus. It is an orthopoxvirus in the family Poxviridae and subfamily Chordopoxvirinae.
Raccoonpox virus | Viral classification
All "Paramyxovirus" virus particles are composed of a ribonucleoprotein core and a lipoprotein bilayer. Avian paramyxoviruses contain a viral envelope that encapsulates a spherical viral capsid containing the negative-sense RNA genome. The members of the "Paramyxoviridae" family, including "Avian metaavulavirus 2", follow the 'rule of six,' having a genome length that is a multiple of six. This allows for proper packing of the genome in the nucleocapsid. The structure of the envelope is characterized by the spike-like projections of two viral proteins, the fusion protein (F) and hemagglutinin-neuraminidase (Hn) protein. However, these protein projections may differ between the nine serotypes of avian paramyxoviruses.
Avian metaavulavirus 2 | Structure
For dsRNA viruses, RdRp transcribes mRNA by using the negative strand as a template. Positive strands may also be used as templates to synthesize negative strands for the construction of genomic dsRNA. dsRNA is not a molecule produced by cells, so cellular life has evolved mechanisms to detect and inactive viral dsRNA. To counter this, dsRNA viruses typically retain their genomes inside of viral capsid in order to evade the host's immune system.
Orthornavirae | Double-stranded RNA viruses
Totiviridae is a family of double-stranded RNA viruses. Giardia lamblia, leishmania, trichomonas vaginalis, and fungi serve as natural hosts. The name of the group derives from Latin "toti" which means undivided or whole. There are currently 28 species in this family, divided among 5 genera.
Totiviridae | Introduction
These viruses consist of two types, however both share the fact that replication is primarily in the cytoplasm, and that replication is not as dependent on the cell cycle as that of DNA viruses. This class of viruses is also one of the most-studied types of viruses, alongside the double-stranded DNA viruses.
Viral replication | Classes 4 & 5: Single-stranded RNA viruses
Viruses in Polydnaviridae are enveloped, with prolate ellipsoid and cylindrical geometries. Genomes are circular and segmented, composed of multiple segments of double-stranded, superhelical DNA packaged in capsid proteins. They are around 2.0–31kb in length.
Polydnavirus | Structure
The conversion from single-stranded to double-stranded form is carried out by the host's own DNA polymerase. The host's RNA polymerase binds to the viral genome and syntheses RNA. Some of this RNA is translated and the remainder is used to initiate DNA replication.
Plectrovirus | Conversion to double stranded form
"Lenarviricota" is the second +ssRNA phylum. It contains the family "Leviviridae", which infect prokaryotes, and the apparent descendants of leviviruses, which infect eukaryotes. The phylum is divided into four classes: "Allassoviricetes", which contains leviviruses and their relatives, "Amabiliviricetes", which contains narnaviruses and their relatives, "Howeltoviricetes", which contains mitoviruses and their relatives, and "Miaviricetes", which contains botourmiaviruses and their relatives. Based on phylogenetic analysis of RdRp, all other RNA viruses are considered to comprise a sister clade in relation to "Lenarviricota".
Positive-strand RNA virus | "Lenarviricota"
Arteriviridae is a family of viruses in the suborder "Arnidovirineae". Members of the family are known as arteriviruses. Positive strand RNA virus, virions are enveloped, spherical, and 45–60 nm in diameter.
Arteriviridae | Introduction