Reverse transcribing virus
A reverse transcribing virus is any virus which replicates using reverse transcription, the formation of DNA from an RNA template. Both Group VI and Group VII viruses fall into this category. Group VI contains single-stranded RNA viruses which use a DNA intermediate to replicate, whereas Group VII contains double-stranded DNA viruses which use an RNA intermediate during genome replication.
All members of Group VI use virally encoded reverse transcriptase, an RNA-dependent DNA polymerase, to produce DNA from the initial virion RNA genome. This DNA is often integrated into the host genome, as in the case of retroviruses and pseudoviruses, where it is replicated and transcribed by the host.
Group VI includes:
Both families in Group VII have DNA genomes contained within the invading virus particles. The DNA genome is transcribed into both mRNA, for use as a transcript in protein synthesis, and pre-genomic RNA, for use as the template during genome replication. Virally encoded reverse transcriptase uses the pre-genomic RNA as a template for the creation of genomic DNA.
Group VII includes:
- Family Hepadnaviridae - e.g. Hepatitis B virus
- Family Caulimoviridae - e.g. Cauliflower mosaic virus