Murine polyomavirus

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Mus musculus polyomavirus 1
A rendering of an icosahedral viral capsid comprising 72 pentamers of VP1, colored such that areas of the surface closer to the interior center appear blue and areas further away appear red.
The
capsid structure comprising 72 pentamers, colored by distance from the interior center. From PDB: 1SIE​.[1]
Virus classification Edit this classification
(unranked): Virus
Realm: Monodnaviria
Kingdom: Shotokuvirae
Phylum: Cossaviricota
Class: Papovaviricetes
Order: Sepolyvirales
Family: Polyomaviridae
Genus: Alphapolyomavirus
Species:
Mus musculus polyomavirus 1

Murine polyomavirus (also known as mouse polyomavirus, Polyomavirus muris, or Mus musculus polyomavirus 1, and in older literature as SE polyoma or parotid tumor virus; abbreviated MPyV) is an unenveloped

tumors, particularly in the parotid gland, in newborn mice was reported by Ludwik Gross in 1953[4] and identified as a virus by Sarah Stewart and Bernice Eddy at the National Cancer Institute, after whom it was once called "SE polyoma".[5][6][7] Stewart and Eddy would go on to study related polyomaviruses such as SV40 that infect primates, including humans. These discoveries were widely reported at the time and formed the early stages of understanding of oncoviruses.[8][9]

Pathology

MPyV is primarily spread among mice via the

maternal antibodies have been shown to be critical in protecting neonates.[3][10][11] It has been described as rare in modern laboratory mouse research colonies.[7]

MPyV is also capable of infecting and causing tumors in other rodent species, including guinea pigs, hamsters, and rats, though the diversity of tissue types giving rise to tumors is reduced in these species.[10]: 107–9  MPyV does not infect humans and is not associated with human cancers.[12]

Structure

3D printed
model of a polyomavirus capsid.

Like other members of the polyomavirus family, MPyV has an unenveloped

sequence similarity to each other, with VP3 truncated at the N-terminus relative to VP2. VP2 and VP3 assemble inside the capsid in contact with VP1.[3][13]

A rendered capsid image with the symmetry-related VP1 monomers shown in different colors and centered on a strict pentamer, producing a radial symmetry effect.
A capsid structure colored to illustrate the assembly of the icosahedral architecture from VP1 pentamers. Each symmetry-related VP1 monomer is shown in a different color. From PDB: 1SIE​.

VP1 is capable of self-assembly into

disulfide bonds.[15]

Genome

MPyV has a closed,

noncoding DNA containing the origin of replication and promoter and enhancer elements.[16]: 786–7  Expression of a microRNA from a region overlapping one of the LT exons has also been identified and is thought to be involved in downregulating expression of the tumor antigens.[17]

Replication

Cellular entry

Viruses lacking a

Unlike many viruses that enter the cell through endocytosis, polyomaviruses penetrate the cell membrane and enter the

protein disulfide isomerase family, has been shown to disrupt the conformation of VP1.[24] It is not known whether entry into the cytosol is obligatory for MPyV infection or whether the particle could enter the cell nucleus directly from the ER. Even a single viral particle entering the nucleus can be sufficient for infection.[21]

Virion assembly

virus factories in which new virions are produced. Red indicators point to tubular structures (arrow: empty tubule; arrowhead: filled tubule) and blue indicators point to virions (arrow: empty virion; arrowhead: filled virion). The dense center of the filled structures likely indicates the presence of virus genomic DNA.[25]

New MPyV

polymerized VP1 have been observed in the nuclei of infected cells as intermediates in the assembly process from which mature virions are produced.[25][27]

Tumorigenesis

MPyV contains three proteins extensively studied for their ability to induce

models for cancer progression and metastasis, particularly of breast cancer.[31][32][33]

Taxonomy

In the 2015 taxonomic update to the polyomavirus group, the

genus Alphapolyomavirus under its new official name Mus musculus polyomavirus 1.[34]

References

Media related to MPyV-infected nuclei and MPyV virus factories at Wikimedia Commons