Molecular biology
VIRION
Non-enveloped, round, icosahedral symmetry (T=1), about 20 nm in diameter. The capsid consists of 12 pentagonal trumpet-shaped pentomers.
GENOME
Monopartite, circular, single-stranded DNA of about 1.8 to 3.8 kb.
The genome is replicated through double-stranded intermediates. The replication (Rep) protein initiates rolling-circle replication.
GENE EXPRESSION
One or two mRNAs encode for the Rep, capsid, and possibly others proteins. Some mRNA can be spliced.
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 with the participation of cellular factors.
- viral mRNAs are transcribed and translated to produce viral proteins.
- Replication may be mediated by a Rep protein, and would occur by rolling circle producing ssDNA genomes
- These newly synthesized ssDNA can either
a) be converted to dsDNA and serve as a template for transcription/replication
b) be encapsidated by capsid protein and form virions released from the cell by budding