Parapoxvirus (taxid:10257)

VIRION

Enveloped, ovoid virion, 220-300nm long and 140-170nm wide. The surface membrane displays surface filaments. Two distinct infectious virus particles exists: the intracellular mature virus (IMV) and the extracellular enveloped virus (EEV).

GENOME

Linear, dsDNA genome of 130-150kb. The linear genome is flanked by inverted terminal repeat (ITR) sequences which are covalently-closed at their extremities.
_Bovine papular stomatitis virus strain BV-AR02_genome at Poxvirus Bioinformatics Ressource center

GENE EXPRESSION

ENZYMES

• DNA-directed DNA polymerase [OPG071]
• DNA-directed RNA polymerase [DdRp]
• Cell-type capping
  • RNA TPase [OPG113]
  • GTase [OPG113]
  • N7MTase [OPG113 + OPG124]
  • 2'O methylase [OPG102]
• Core protease (Peptidase C57) [OPG083]
• Metalloprotease (Peptidase M44) [Protease (OPG085)]

REPLICATION

CYTOPLASMIC

1. Attachement 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

Apoptosis modulation

The orf virus encodes a viral bcl-2 protein (v-Bcl2) that prevents host apoptosis .

NF-kappa-B modulation

Orf virus ORFV121 physically interacts with NF-kappaB-p65 in the cell cytoplasm and thereby inhibits host NF-kappaB signaling pathway .

Cell cycle modulation

The poxvirus anaphase promoting complex regulator (PACR) promotes viral replication by manipulating the anaphase promoting complex/cyclosome (APC/C), thus promoting the host differentiated G0 cells to enter G1 .