Avsunviroidae

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1 Avsunviroidae
2 Replication
3 Structure
4 References

[edit] Avsunviroidae

The Avsunviroidae are a family of viroids. At present three members are known of. They consist of RNA genomes between 246-375 nucleotides in length. They are single stranded covalent circles and have intramolecular base pairing. All members lack a central conserved region.

[edit] Replication

Key features of replication include no helper virus required and no proteins are encoded for. Unlike the other family of viroids, Pospiviroidae, Avsunviroidae are thought to replicate via a symmetrical rolling mechanism. It is thought the positive RNA strand acts as a template to form negative strands with the help of an enzyme thought to be RNA polymerase II. The negative RNA strands are then cleaved by ribozyme activity and circularises. A second rolling circle mechanism forms a positive strand which is also cleaved by ribozyme activity and then ligated to become circular. The site of replication is unknown but it is thought to be in the cytoplasm.

[edit] Structure

Predictions of structure have suggested that they exist either as rod-shaped molecules with regions of base pairing causing formation of some hair pin loops or have branched configurations.

Family Avsunviroidae
- Genus Avsunviroid; type species: Avocado sunblotch viroid
- Genus Pelamoviroid; type species: Peach latent mosaic viroid
- Genus Elaviroid;