''Pseudoviridae'' is a family of
virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...
es, which includes three genera.
Viruses of the family are actually
LTR retrotransposons of the Ty1-copia family. They replicate via structures called
virus-like particles (VLPs). VLPs are not infectious like normal virions, but they nevertheless make up an essential part of the pseudoviral lifecycle.
[
]
Taxonomy
''Pseudoviridae'' is unofficially classified under group VI RNA
Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
Reverse Transcribing Viruses
''Revtraviricetes'' is a class of viruses that contains all viruses that encode a reverse transcriptase. The group includes all ssRNA-RT viruses (including the retroviruses) and dsDNA-RT viruses. It is the sole class in the phylum ''Artverviric ...
and infect fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
and invertebrates
Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...
.
''Pseudoviridae'' comprises highly divergent members and most ''Pseudoviridae'' encode Gag and Pol on a single open reading frame
In molecular biology, reading frames are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames ...
.
''Pseudoviridae'' is included in the order ''Ortervirales'' along with families ''Belpaoviridae
''Semotivirus'' is the only genus of viruses in the family ''Belpaoviridae'' (formerly included in the family ''Metaviridae''). Species exist as retrotransposons in a Eukaryote, eukaryotic host's genome. BEL/pao transposons are only found in anim ...
'', ''Metaviridae
''Metaviridae'' is a family of viruses which exist as Ty3-gypsy LTR retrotransposons in a eukaryotic host's genome. They are closely related to retroviruses: members of the family ''Metaviridae'' share many genomic elements with retroviruses, i ...
'', ''Retroviridae
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase ...
'', and ''Caulimoviridae
''Caulimoviridae'' is a family of viruses infecting plants. The family contains 11 genera. Viruses belonging to the family ''Caulimoviridae'' are termed double-stranded DNA (dsDNA) reverse-transcribing viruses (or pararetroviruses) i.e. viruses ...
''.
The family includes the following genera:[NCBI]
Penicillium camemberti virus – GP1
(species)
* Phaseolus vulgaris Tpv2-6 virus
Genome
The genome
A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...
of viruses from this family is unsegmented, -RT, positive-sense, single-stranded RNA and is 4200–9700 nucleotides
Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...
long. The genome encodes structural proteins and non-structural proteins
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, re ...
which codes for an RNA-dependent DNA polymerase, replicase, and reverse transcriptase
A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, by retrotransposon mobi ...
for the reverse transcription
A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B virus, hepatitis B to replicate their genomes, by retrot ...
step during replication.
Structure
The viral capsid
A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or m ...
is unenveloped and looks roughly spherical. The capsid is round with icosahedral symmetry with triangulation number
A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or ma ...
(T) = 3 and 4. It is also isometric to quasi-isometric and has a diameter
In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...
of 30–50 nm. LTR-retrotransposons
Retrotransposons (also called Class I transposable elements) are transposable element, mobile elements which move in the host genome by converting their transcribed RNA into DNA through reverse transcription. Thus, they differ from Class II trans ...
are poorly characterized and lipids
Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins Vitamin A, A, Vitamin D, D, Vitamin E, E and Vitamin K, K), monoglycerides, diglycerides, phospholipids, and others. The fu ...
have not reported.
Replication
The genome integrates into the host genome and gets transcribed by host cell enzymes
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as pro ...
such as eukaryotic
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
nuclear RNA polymerase II
RNA polymerase II (RNAP II and Pol II) is a Protein complex, multiprotein complex that Transcription (biology), transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNA pol ...
. Genome replication takes place in the host cytoplasm
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
, or the nucleus and assembly can occur in the cytoplasm, or in the nucleus.
References
External links
ICTV Report: ''Pseudoviridae''Pseudoviridae
(Darwin Zoology)
{{Taxonbar, from=Q3772842
RNA reverse-transcribing viruses
Virus families
Ortervirales