Betaretrovirus

VIRION

Enveloped, spherical to pleomorphic in shape, 80-100 nm in diameter.

GENOME

Monopartite, linear, dimeric, ssRNA(+) genome of about 8-10 kb, with a 5'-cap and a 3’poly-A tail. There are two long terminal repeats (LTRs) of about 600nt long at the 5' and 3' ends. The LTRs contain the U3, R, and U5 regions. There are also a primer binding site (PBS) at the 5’end and a polypurine tract (PPT) at the 3’end.

GENE EXPRESSION

The integrated provirus utilizes the promoter elements in the 5’LTR to drive transcription. This gives rise to the unspliced full length mRNA that will serve as genomic RNA to be packaged into virions or used as a template for translation of gag, gag-pro (1 ribosomal frameshift), and gag-pro-pol (2 ribosomal frameshifts) polyproteins. The spliced mRNAs encode env that is cleaved into SU and TM envelope proteins and sag, a superantigen encoded at the 3’end of the MMTV genome.

REPLICATION

NUCLEAR

  1. Virus attaches to host receptors through the SU glycoprotein. TM glycoprotein mediates fusion with cell membrane.
  2. Internalization and partial uncoating.
  3. ssRNA(+) genome is copied into a linear dsDNA molecule by the reverse transcriptase.
  4. Nuclear entry of the viral dsDNA when the nuclear membrane is disassembled at mitosis.
  5. Viral dsDNA is covalently and randomly integrated into the cell’s genome by the viral integrase (=provirus).
  6. Transcription of provirus by Pol II produces viral spliced and unspliced RNAs.
  7. Nuclear export of the incompletely spliced RNAs.
  8. Translation of unspliced viral RNAs produces Env, Gag and Gag-Pol polyproteins.
  9. Assembly of the virion as intracytoplasmic particles.
  10. Intracytoplasmic particles relocate to the plasma membrane, become enveloped, and are released.
  11. Proteolytic processing of the precursors polyproteins by viral protease and maturation of the virions.

Host-virus interaction

Superantigen

Mouse Mammary Tumour virus expresses a superantigen to evade innate immune response

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Matching UniProtKB/Swiss-Prot entries

36 entries grouped by protein (browse by keywords)

All proteins are shown (view only 26 complete proteome entries)

9 entries

Envelope glycoprotein (Env polyprotein)

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ENV_MMTVC
Mouse mammary tumor virus (strain C3H) (MMTV) reference strain

Envelope glycoprotein gp70 (Env polyprotein)

ENV_JSRV
Sheep pulmonary adenomatosis virus (Jaagsiekte sheep retrovirus) (JSRV)
ENV_MMTVB
Mouse mammary tumor virus (strain BR6) (MMTV)

Envelope glycoprotein gp70 (Env polyprotein)

ENV_MMTVG
Mouse mammary tumor virus (strain GR) (MMTV)

Envelope glycoprotein gp70 (Env polyprotein)

ENV_MPMV
Mason-Pfizer monkey virus (MPMV) (Simian Mason-Pfizer virus)
ENV_SMRVH
Squirrel monkey retrovirus (SMRV-H) (SMRV-HLB)
ENV_SRV1
Simian retrovirus SRV-1
ENV_SRV2
Simian retrovirus SRV-2
ENV_SRV2R
Simian retrovirus SRV-2 (isolate 2R-18B1)

7 entries

Gag polyprotein (Core polyprotein)

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GAG_MMTVC
Mouse mammary tumor virus (strain C3H) (MMTV) reference strain

Gag polyprotein

GAG_JSRV
Sheep pulmonary adenomatosis virus (Jaagsiekte sheep retrovirus) (JSRV)

Gag polyprotein

GAG_MMTVB
Mouse mammary tumor virus (strain BR6) (MMTV)

Gag polyprotein

GAG_MPMV
Mason-Pfizer monkey virus (MPMV) (Simian Mason-Pfizer virus)
GAG_SMRVH
Squirrel monkey retrovirus (SMRV-H) (SMRV-HLB)

Gag polyprotein

GAG_SRV1
Simian retrovirus SRV-1
GAG_SRV2
Simian retrovirus SRV-2

7 entries

Pol polyprotein

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POL_MMTVC
Mouse mammary tumor virus (strain C3H) (MMTV) reference strain

Gag-Pro-Pol polyprotein

POL_JSRV
Sheep pulmonary adenomatosis virus (Jaagsiekte sheep retrovirus) (JSRV)
POL_MMTVB
Mouse mammary tumor virus (strain BR6) (MMTV)
POL_MPMV
Mason-Pfizer monkey virus (MPMV) (Simian Mason-Pfizer virus)
POL_SMRVH
Squirrel monkey retrovirus (SMRV-H) (SMRV-HLB)
POL_SRV1
Simian retrovirus SRV-1
POL_SRV2
Simian retrovirus SRV-2

3 entries

Protein PR73

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PR73_MMTVC
Mouse mammary tumor virus (strain C3H) (MMTV) reference strain

Protein PR73 (Superantigen) (Sag)

PR73_MMTVB
Mouse mammary tumor virus (strain BR6) (MMTV)
PR73_MMTVG
Mouse mammary tumor virus (strain GR) (MMTV)

1 entry

Protein PR73 5'-endogenous

PR7L_MMTVG
Mouse mammary tumor virus (strain GR) (MMTV)

1 entry

Protein PR73 3'-endogenous

PR7R_MMTVG
Mouse mammary tumor virus (strain GR) (MMTV)

1 entry

Gag-Pro polyprotein

PRO_MMTVC
Mouse mammary tumor virus (strain C3H) (MMTV) reference strain

6 entries

Protease (EC 3.4.23.-)

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VPRT_JSRV
Sheep pulmonary adenomatosis virus (Jaagsiekte sheep retrovirus) (JSRV)

Bifunctional protease/dUTPase

VPRT_MMTVB
Mouse mammary tumor virus (strain BR6) (MMTV)
VPRT_MPMV
Mason-Pfizer monkey virus (MPMV) (Simian Mason-Pfizer virus)
VPRT_SMRVH
Squirrel monkey retrovirus (SMRV-H) (SMRV-HLB)
VPRT_SRV1
Simian retrovirus SRV-1
VPRT_SRV2
Simian retrovirus SRV-2

1 entry

Protein Vpu (ORF-X protein)

VPU_JSRV
Sheep pulmonary adenomatosis virus (Jaagsiekte sheep retrovirus) (JSRV)