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

1. Virus particle attaches to target cell via g3p protein binding to F pilus. Pilus retraction pulls the virion to the host internal membrane.
2. Injection of the viral DNA into the host cytoplasm.
3. Host polymerase convert the (+)ssDNA viral genome into a covalently closed dsDNA called replicative form DNA RF.
4. viral genes are transcribed by host RNA polymerase.
5. Viral g2p protein nicks RF DNA strand at the origin of replication.
6. (+)strand replication occurs by rolling circle.
7. New (+)ssDNA genomes are converted into new RF molecules, and further transcription occurs.
8. When enough g5p protein is synthesized, conversion into RF dsDNA is inhibited, as neo-synthesized genomic ssDNA is covered with g5p.
9. g5p are replaced by g8p proteins to assemble the viral capsid.
10. new virions bud out from host cell.
11. Infected cell continue to divide and produces virion indefinitely.