Subfamily: Spumaretrovirinae
Family: Retroviridae
Subfamily: Spumaretrovirinae
Viruses in this genus are most similar to viruses in the genus Gammaretrovirus, but can be distinguished based on RT-based phylogenetic clustering, by the presence of the regulatory genes tax and rex, and in some viruses, the unusual presence of an hbz gene on the antisense strand.
Virions can have “B-type” or “D-type” morphology, depending on the species. Genomes typically contain an additional regulatory gene that overlaps with the env gene and is encoded by a multiply-spliced mRNA – examples include the rem gene of MMTV and the rej gene of JSRV.
Virus particles assemble at the plasma membrane and exhibit a “C-type” morphology. Viruses in the genus have an envelope TM protein with an internal fusion peptide flanked by two cysteines, whereas viruses in the other genera typically have an N-terminal fusion peptide. Many oncogene-containing members of the genus have been isolated.
A summary of this ICTV Report chapter has been published as an ICTV Virus Taxonomy Profile article in the Journal of General Virology, and should be cited when referencing this online chapter as follows:
Coffin et al., 2021, ICTV Virus Taxonomy Profile: Retroviridae 2021, Journal of General Virology, 2021;102:001712.
Aiewsakun, P. and A. Katzourakis (2015). Endogenous viruses: Connecting recent and ancient viral evolution. Virology 479-480: 26-37. [PubMed]