Mouse mammary tumor virus
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| Mouse mammary tumor virus | |
|---|---|
Virus classification  | |
| (unranked): | Virus |
| Realm: | Riboviria |
| Kingdom: | Pararnavirae |
| Phylum: | Artverviricota |
| Class: | Revtraviricetes |
| Order: | Ortervirales |
| Family: | Retroviridae |
| Genus: | Betaretrovirus |
| Species: | Betaretrovirus murmamtum |
Mouse mammary tumor is a milk-transmitted retrovirus (MMTV), similar to BLV, HI, and HTL viruses. It is a member of the betaretrovirus genus.
When John Joseph Bittner was employed at the Jackson Laboratory in Bar Harbor, Maine, in 1936, he proved the extra-chromosomal vertical transmission of murine breast cancer through adoptive nursing. This process was known as the "milk factor" or Bittner virus. Bittner developed the hypothesis that a virus in the mother's milk may spread a carcinogenic agent, or "milk factor," from malignant mothers to young mice. The mouse mammary tumor virus is the primary cause of most mammary cancers in mice.
The virus is vertically transferred from mother to pup by milk, but it is also endogenously carried by a number of mouse strains. It is present in milk lymphocytes as a DNA provirus that is integrated into their DNA. The viruses go to the Peyer's patches via the gastrointestinal system, where they infect the macrophages and subsequently the lymphocytes of the new host.
It was previously thought that the mouse mammary tumor virus was a simple retrovirus. However, it has recently been determined that MMTV is the first complex murine retrovirus to be identified because it encodes an additional self-regulatory mRNA export protein, Rem, that is similar to the HIV Rev protein. Rem seems to go back and forth between the cytoplasm and the nucleus. The HIV-1 Rev protein promotes the cytoplasmic accumulation of both unspliced and singly-spliced mRNAs, as opposed to Rem, which exports only unspliced gag/pol mRNA.