Molecular biology
VIRION
Non-enveloped, Rod shaped about 10-16nm in diameter and 70-280nm long.
GENOME
Circular, single-stranded DNA of 4.5 to 8kb encoding for 4 to 10 proteins. Replication occurs via dsDNA intermediate and rolling circle.
GENE EXPRESSION
Each gene is transcribed by host cellular machinery, via a specific promoter. Some genes ends by a transcription terminator.
REPLICATION
CYTOPLASMIC
- Virus particle attaches to target cell via g3p protein binding to F pilus. Pilus retraction pulls the virion to the host internal membrane.
- Injection of the viral DNA into the host cytoplasm.
- Host polymerase convert the (+)ssDNA viral genome into a covalently closed dsDNA called replicative form DNA RF.
- viral genes are transcribed by host RNA polymerase.
- Viral g2p protein nicks RF DNA strand at the origin of replication.
- (+)strand replication occurs by rolling circle.
- New (+)ssDNA genomes are converted into new RF molecules, and further transcription occurs.
- When enough g5p protein is synthesized, conversion into RF dsDNA is inhibited, as neo-synthesized genomic ssDNA is covered with g5p.
- g5p are replaced by g8p proteins to assemble the viral capsid.
- new virions bud out from host cell.
- Infected cell continue to divide and produces virion indefinitely.