Satellite virus: infection requires host cell to be co-infected with helper virus
VIRION
Enveloped, spherical about 22 nm in diameter. The virion is covered by helper virus membrane proteins.
GENOME
Circular, ssRNA(-) genome of 1,68 kb. Most of the genome displays complementary strands. Replication occurs by rolling circle, single genome being cleaved/ligated by ribozymes.
GENE EXPRESSION
Encodes for one protein. in Deltavirus, genome editing by host ADAR1 extends the S-HDAg ORF by 19 amino acids, inducing production of L-HDAg. Edited genome seems to be unable to replicate.
REPLICATION
NUCLEAR
- Virion attaches to host receptors though helper virus surface protein.
- Fusion of virus membrane with the vesicle membrane; the RNA genome is released in the cytoplasm and migrates to the nucleus.
- Transcription of the single viral gene, promoting viral transcription and replication
- Symmetrical rolling circle replication by host DNA-dependent RNA polymerase II
- later, genomic RNA can be edited by host ADAR1, inducing packaging of viral genome at the RE.
- Budding by helper viral proteins.