Leporipoxvirus (taxid:10270)

VIRION

Enveloped, brick-shaped 300x250x200nm. The surface membrane displays surface tubules or surface filaments. Two distinct infectious virus particles exists: the intracellular mature virus (IMV) and the extracellular enveloped virus (EEV).

GENOME

Linear, dsDNA genome of 160kb. The linear genome is flanked by inverted terminal repeat (ITR) sequences which are covalently-closed at their extremities.
Myxoma virus strain Lausanne genome at Poxvirus Bioinformatics Ressource center

GENE EXPRESSION

ENZYMES

• DNA dependent DNA polymerase
• DNA dependent RNA polymerase
• Cell-type capping
  • RNA TPase
  • GTase
  • N7MTase
  • 2'O methylase
• Core protease (Peptidase C57)
• Metalloprotease (Peptidase M44)

REPLICATION

CYTOPLASMIC

1. Attachment of the viral proteins to host glycosaminoglycans (GAGs) mediates endocytosis of the virus into the host cell.
2. Fusion with the plasma membrane to release the core into the host cytoplasm.
3. Early phase: early genes are transcribed in the cytoplasm by viral RNA polymerase. Early expression begins at 30 minutes post-infection.
4. Core is completely uncoated as early expression ends, viral genome is now free in the cytoplasm.
5. Intermediate phase: Intermediate genes are expressed, triggering genomic DNA replication at approximately 100 minutes post-infection.
6. Late phase: Late genes are expressed from 140 min to 48 hours post-infection, producing all structural proteins.
7. Assembly of progeny virions starts in cytoplasmic viral factories, producing an spherical immature particle. This virus particle matures into brick-shaped intracellular mature virion (IMV).
8. IMV virion can be released upon cell lysis, or can acquire a second double membrane from trans-Golgi and bud as external enveloped virion (EEV).

Host-virus interaction

Adaptive immune response inhibition

The poxviral E3 ubiquitin-protein ligase LAP promotes ubiquitination and subsequent degradation of host MHC-I and CD4 molecules .

Apoptosis modulation

Myxoma virus M11L inhibits host apoptosis by preventing the conformational activation of host Bax at the mitochondria .

Cell-cycle modulation

The myxomavirus Ankyrin repeat domain-containing protein M-T5 is an adapter of SKP1-containing E3 ubiquitin-protein ligases which mediate the ubiquitination and subsequent proteasomal degradation of host target proteins including CDKN1B. Disappearance of host CDKN1B correlates with cell cycle progression through the G0/G1 checkpoint .