Mouse Mammary Tumor Viruses (MMTVs) are B-type retroviral inductors of mammary carcinogenesis and lymphoma in the T-cells of mice. This kind of retroviruses can be either exogenous (transmitted through milk) or endogenous (Bittner 1936; Callahan et al. 1982; Moore et al. 1987). MMTVs belong to the genus Betaretrovirus, which is comprised of both B- and D-type retroviruses. Interestingly, D-type betaretroviruses present a common surface receptor also used by the baboon and cat endogenous C-type gammaretroviruses (BaEVM, RD114), cellular infection by any of them can interfere with other D-type members, and also with BaEVM and RD114 (Chatterjee and Hunter 1980; Sommerfelt and Weiss 1990). This evidence seems to be related with the high similarity displayed between env polyproteins encoded by gammaretroviruses and D-type betaretroviruses, indicating that betaretroviruses and gammaretroviruses may have been involved in an ancient recombinatorial event (Sonigo et al. 1986; Fauquet et al. 2005) or that they share a common ancestor (see env tree in section "phylogenies").

The genomic structure of a typical MMTV is 8.8-9.9 Kb in size including pro-5´LTR of 135 nt and a long pro-3´LTR of 1.4 Kb. The internal region displays a Primer Binding Site (PBS) complementary to a tRNALys-3, Open Reading Frames (ORFs) for gag, dut/pro, pol, and env genes, an ORF for an accessory gene sag that encompasses the U3 3´LTR and env regions and codify for a 37-kDa type-II transmembrane glycoprotein known as superantigen (Sag), and a Polypurine Tract (PPT) adjacent to the 3´LTR (Moore et al. 1987; Acha-Orbea and Macdonald. 1995; Brandt-carlson and Butel 1991; Choi, Kappler and Marrack 1991; Choi, Marrack and Kappler 1992; Krummenacher and Diggelmann 1993; Yazdanbakhsh et al. 1993; Wrona et al. 1998; Elder et al. 1992; Payne and Elder 2001). We also have found that MMTV also presents a putative accessory gene Orf-x that is common among many other betaretroviruses, and that was originally described in JSRV betaretroviruses (Bai et al. 1999; Rosati et al. 2000).



Figure not to scale. If present, long terminal repeats (LTRs) have been highlighted in blue. Amino acid motifs noted with lines indicate the conserved residues in each protein domain, abbreviations below mean:

MA=matrix PR=protease DU or DUT=dUTPase TM=transmembrane TAV or IBMP=transactivator/viroplasmin or inclusion body matrix protein
CA=capsid RT=reverse transcriptase INT=Integrase CHR=chromodomain
NC=nucleocapsid RH=RNaseH SU=surface MOV=movement protein
PPT=polypurine tract PBS=primer binding site ATF=aphid transmission factor VAP=virion associated protein

Related literature

Genbank accession: AF033807
Clade: Undetermined
Cluster or genus: Betaretrovirus
Branch or class: Class 2
Family: Retroviridae
System: LTR retroelements
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Welcome to the Gypsy Database (GyDB) an open editable database about the evolutionary relationship of viruses, mobile genetic elements (MGEs) and the genomic repeats where we invite all authors to contribute with their knowledge to improve and expand the topics.
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Llorens, C., Futami, R., Covelli, L., Dominguez-Escriba, L., Viu, J.M., Tamarit, D., Aguilar-Rodriguez, J. Vicente-Ripolles, M., Fuster, G., Bernet, G.P., Maumus, F., Munoz-Pomer, A., Sempere, J.M., LaTorre, A., Moya, A. (2011) The Gypsy Database (GyDB) of Mobile Genetic Elements: Release 2.0 Nucleic Acids Research (NARESE) 39 (suppl 1): D70-D74 doi: 10.1093/nar/gkq1061

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