Molecular biology


Enveloped. Spherical to pleomorphic, about 80-100 nm in diameter.


Monopartite, linear, dimeric, ssRNA(+) genome of 8.4-9 kb, with a 5’-cap and a 3’poly-A tail. There are two long terminal repeats (LTRs) of about 550-750 nt 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.


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 singly spliced mRNA encodes env that is cleaved into SU and TM envelope proteins. Completely spliced mRNAs encode Rex and Tax. Rex escorts unspliced and singly spliced RNAs out of the nucleus of infected cells. Tax is a transcriptional activator that activates viral and cellular genes.



Lytic replication:

  1. Virus attaches to host receptors through the SU glycoprotein. TM glycoprotein mediates fusion with cell membrane.
  2. Internalization and 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. Translation of fully spliced viral RNAs produces tax and rex proteins.
  8. Rex mediates nuclear export of the incompletely spliced RNAs.
  9. Translation of unspliced viral RNAs produces Env, Gag, Gag-Pro and Gag-Pro-Pol polyproteins.
  10. Assembly of the virion at the host cellular membrane and packaging of the viral RNA genome.
  11. Budding through the plasma membrane and release of the virions.
  12. Proteolytic processing of the precursors polyproteins by viral protease and maturation of the virions.

Latent replication : replication as a provirus integrated in the host chromosome.

Matching UniProtKB/Swiss-Prot entries

61 entries grouped by strain (browse by keywords)

All proteins are shown (view only 36 complete proteome entries)

9 entries

Human T-cell leukemia virus 1 (isolate Caribbea HS-35 subtype A) (HTLV-1) reference strain

Select_all Deselect_all  
ENV_HTL1CEnvelope glycoprotein gp62 (Env polyprotein)
GAG_HTL1CGag polyprotein (Pr53Gag)
HBZ_HTL1CHTLV-1 basic zipper factor (HBZ)
P12I_HTL1CAccessory protein p12I
P30II_HTL1CAccessory protein p30II
POL_HTL1CGag-Pro-Pol polyprotein (Pr160Gag-Pro-Pol)
PRO_HTL1CGag-Pro polyprotein (Pr76Gag-Pro)
REX_HTL1CProtein Rex (Rev homolog) (Rex-1) (p27Rex)
TAX_HTL1CProtein Tax-1 (Protein X-LOR) (Protein PX) (Trans-activating transcriptional ...

6 entries

Human T-cell leukemia virus 2 (HTLV-2) reference strain

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ENV_HTLV2Envelope glycoprotein gp63 (Env polyprotein)
GAG_HTLV2Gag polyprotein (Pr53Gag)
POL_HTLV2Gag-Pro-Pol polyprotein (Pr160Gag-Pro-Pol)
PRO_HTLV2Gag-Pro polyprotein (Pr76Gag-Pro)
REX_HTLV2Protein Rex (Rev homolog) (Rex-2)
TAX_HTLV2Protein Tax-2 (Trans-activating transcriptional regulatory protein of HTLV-2)

6 entries

Human T-cell leukemia virus 3 (strain 2026ND) (HTLV-3) reference strain

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ENV_HTL32Envelope glycoprotein gp63 (Env polyprotein)
GAG_HTL32Gag polyprotein (Pr53Gag)
POL_HTL32Gag-Pro-Pol polyprotein (Pr160Gag-Pro-Pol)
PRO_HTL32Gag-Pro polyprotein (Pr76Gag-Pro)
REX_HTL32Protein Rex (Rev homolog) (Rex-3)
TAX_HTL32Protein Tax-3 (Trans-activating transcriptional regulatory protein of HTLV-3)

9 entries

Human T-cell leukemia virus 1 (strain Japan ATK-1 subtype A) (HTLV-1)

Select_all Deselect_all  
ENV_HTL1AEnvelope glycoprotein gp62 (Env polyprotein)
GAG_HTL1AGag polyprotein (Pr53Gag)
HBZ_HTL1AHTLV-1 basic zipper factor (HBZ)
P12I_HTL1AAccessory protein p12I
P30II_HTL1AAccessory protein p30II
POL_HTL1AGag-Pro-Pol polyprotein (Pr160Gag-Pro-Pol)
PRO_HTL1AGag-Pro polyprotein (Pr76Gag-Pro)
REX_HTL1AProtein Rex (Rev homolog) (Rex-1) (p27Rex)
TAX_HTL1AProtein Tax-1 (Protein X-LOR) (Protein PX) (Trans-activating transcriptional ...

7 entries

Human T-cell leukemia virus 1 (isolate Melanesia mel5 subtype C) (HTLV-1)

Select_all Deselect_all  
ENV_HTL1LEnvelope glycoprotein gp62 (Env polyprotein)
GAG_HTL1LGag polyprotein (Pr53Gag)
HBZ_HTL1LHTLV-1 basic zipper factor (HBZ)
POL_HTL1LGag-Pro-Pol polyprotein (Pr160Gag-Pro-Pol)
PRO_HTL1LGag-Pro polyprotein (Pr76Gag-Pro)
REX_HTL1LProtein Rex (Rev homolog) (Rex-1) (p27Rex)
TAX_HTL1LProtein Tax-1 (Protein X-LOR) (Trans-activating transcriptional regulatory ...

6 entries

Human T-cell leukemia virus 3 (strain Pyl43) (HTLV-3)

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ENV_HTL3PEnvelope glycoprotein gp63 (Env polyprotein)
GAG_HTL3PGag polyprotein (Pr53Gag)
POL_HTL3PGag-Pro-Pol polyprotein (Pr160Gag-Pro-Pol)
PRO_HTL3PGag-Pro polyprotein (Pr76Gag-Pro)
REX_HTL3PProtein Rex (Rev homolog) (Rex-3)
TAX_HTL3PProtein Tax-3 (Trans-activating transcriptional regulatory protein of HTLV-3)

4 entries

Bovine leukemia virus (isolate Japanese BLV-1) (BLV)

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ENV_BLVJEnvelope glycoprotein (Env polyprotein)
GAG_BLVJGag polyprotein
POL_BLVJPol polyprotein
VPRT_BLVJProtease (EC 3.4.23.-)

3 entries

Bovine leukemia virus (isolate Australian) (BLV)

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ENV_BLVAUEnvelope glycoprotein (Env polyprotein)
GAG_BLVAUGag polyprotein
POL_BLVAUPol polyprotein

3 entries

Human T-cell leukemia virus 1 (isolate Zaire EL subtype B) (HTLV-1)

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ENV_HTL1FEnvelope glycoprotein gp62 (Env polyprotein)
REX_HTL1FProtein Rex (Rev homolog) (Rex-1) (p27Rex)
TAX_HTL1FProtein Tax-1 (Protein X-LOR) (Trans-activating transcriptional regulatory ...

2 entries

Human T-cell leukemia virus 1 (strain Japan MT-2 subtype A) (HTLV-1)

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ENV_HTL1MEnvelope glycoprotein gp62 (Env polyprotein)
GAG_HTL1MGag polyprotein (Pr53Gag)

1 entry

Bovine leukemia virus (BLV)

ENV_BLVEnvelope glycoprotein (Env polyprotein)

1 entry

Bovine leukemia virus (isolate American FLK) (BLV)

ENV_BLVAFEnvelope glycoprotein (Env polyprotein)

1 entry

Bovine leukemia virus (isolate American VDM) (BLV)

ENV_BLVAVEnvelope glycoprotein (Env polyprotein)

1 entry

Bovine leukemia virus (isolate Belgium LB285) (BLV)

ENV_BLVB2Envelope glycoprotein (Env polyprotein)

1 entry

Bovine leukemia virus (isolate Belgium LB59) (BLV)

ENV_BLVB5Envelope glycoprotein (Env polyprotein)

1 entry

Human T-cell leukemia virus 1 (isolate Caribbea CH subtype A) (HTLV-1)

ENV_HTL1NEnvelope glycoprotein gp62 (Env polyprotein)