Molecular biology
VIRION
Non-enveloped, round, icosahedral symmetry (T=1), 21-22 nm in diameter. The capsid consists of 60 copies of CP protein.
GENOME
Linear, single-stranded DNA of about 4kb in size, with long inverted terminal repeats. both positive and negative strand are encapsidated, but majority is of negative polarity (85%).
The genome is replicated through rolling-hairpin mechanism.
GENE EXPRESSION
Host proteins transcribe the genomes into mRNAs.
REPLICATION
NUCLEAR
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic ssDNA into the nucleus.
- The ssDNA is converted into dsDNA by cellular proteins.
- viral mRNAs are transcribed when host cell enters S phase and translated to produce viral proteins.
- Replication occurs through rolling-hairpin mechanism, with NS1 nickase binding covalently to the 5’ genomic end.
- Individual ssDNA genomes are excised from replication concatemers by a process called junction resolution.
- These newly synthesized ssDNA can either
a) be converted to dsDNA and serve as a template for transcription/replication
b) be encapsidated to form new virions that can bud out of the host cell.