Spumavirus

Enveloped. Spherical to pleomorphic, about 80-100 nm in diameter. About 20% of of released viral particles already contains dsDNA genomes. This is due to an unique feature of spumaviruses in which the onset of reverse transcription of genomic RNA occurs before release rather than after entry of the new host cell like in other retroviruses.

GENOME

Monopartite, linear, dimeric, ssRNA(+)/dsDNA (depending on the timing of reverse transcription) genome of about 12 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.

Spumaviruses are considered as promising vectors for the targeted delivery and expression of therapeutic genes or antigens.

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 protein, p3).
The spliced mRNAs encode (pro)pol (PR, RT, RnaseH, IN) and env (Leader peptide, SU, TM). Incompletely spliced mRNAs contain cis-acting sequences that directly bind cellular factors to allow export from the nucleus into the cytoplasm.
The spumaviruses genome contains up to three additional ORFs encoding Bel1, Bel2 and Bel3 that are expressed predominantly by the internal promoter (IP) localized in the env gene. The cytoplasmic Bet protein consists of bel1 and bel2 spliced sequences.

REPLICATION

  1. Virus attaches to host receptors through the SU glycoprotein. TM glycoprotein mediates fusion with cell membrane.
  2. Internalization and uncoating.
  3. ssRNA(+) or dsDNA genome enter the cell. ssRNA is copied into a linear dsDNA molecule by the reverse transcriptase.
  4. Nuclear entry of the viral dsDNA which is covalently and randomly integrated into the cell’s genome by the viral integrase (=provirus).
  5. Transcription of provirus to form viral RNAs and splicing.
  6. Translation of the RNAs to form precursor polyproteins.
  7. Late reverse transcription can occur.
  8. Assembly of the virion and packaging of the viral RNA genome.
  9. Budding predominantly into the endoplasmic reticulum (ER) and occasionally through the plasma membrane, most viral particles remain in the cell.
  10. Proteolytic processing of the precursors polyproteins by viral protease and maturation of the virions.

Matching UniProtKB/Swiss-Prot entries

22 entries grouped by protein (browse by keywords)

All proteins are shown (view only 21 complete proteome entries)

4 entries

Protein Bel-1 (Transactivator of spumavirus) (Tas) (Transcriptional transactivator)

Select_allDeselect_all
BEL1_FOAMV
Human spumaretrovirus (SFVcpz(hu)) (Human foamy virus) reference strain
BEL1_SFV1
Simian foamy virus type 1 (SFVmac) (SFV-1) reference strain
BEL1_SFVCP
Simian foamy virus (isolate chimpanzee) (SFVcpz) reference strain
BEL1_SFV3L
Simian foamy virus type 3 (strain LK3) (SFVagm) (SFV-3)

2 entries

Protein Bel-2

Select_allDeselect_all
BEL2_SFV1
Simian foamy virus type 1 (SFVmac) (SFV-1) reference strain
BEL2_SFV3L
Simian foamy virus type 3 (strain LK3) (SFVagm) (SFV-3)

1 entry

Protein Bel-3

BEL3_FOAMV
Human spumaretrovirus (SFVcpz(hu)) (Human foamy virus) reference strain

2 entries

Protein Bet

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BET_FOAMV
Human spumaretrovirus (SFVcpz(hu)) (Human foamy virus) reference strain
BET_SFVCP
Simian foamy virus (isolate chimpanzee) (SFVcpz) reference strain

4 entries

Envelope glycoprotein gp130 (Env polyprotein)

Select_allDeselect_all
ENV_FOAMV
Human spumaretrovirus (SFVcpz(hu)) (Human foamy virus) reference strain
ENV_SFV1
Simian foamy virus type 1 (SFVmac) (SFV-1) reference strain
ENV_SFVCP
Simian foamy virus (isolate chimpanzee) (SFVcpz) reference strain
ENV_SFV3L
Simian foamy virus type 3 (strain LK3) (SFVagm) (SFV-3)

4 entries

Gag polyprotein (Pr71Gag)

Select_allDeselect_all
GAG_FOAMV
Human spumaretrovirus (SFVcpz(hu)) (Human foamy virus) reference strain
GAG_SFV1
Simian foamy virus type 1 (SFVmac) (SFV-1) reference strain
GAG_SFVCP
Simian foamy virus (isolate chimpanzee) (SFVcpz) reference strain
GAG_SFV3L
Simian foamy virus type 3 (strain LK3) (SFVagm) (SFV-3)

4 entries

Pro-Pol polyprotein (Pr125Pol)

Select_allDeselect_all
POL_FOAMV
Human spumaretrovirus (SFVcpz(hu)) (Human foamy virus) reference strain
POL_SFV1
Simian foamy virus type 1 (SFVmac) (SFV-1) reference strain
POL_SFVCP
Simian foamy virus (isolate chimpanzee) (SFVcpz) reference strain
POL_SFV3L
Simian foamy virus type 3 (strain LK3) (SFVagm) (SFV-3)

1 entry

Putative uncharacterized protein S1

S1_FOAMV
Human spumaretrovirus (SFVcpz(hu)) (Human foamy virus)