Notes on Family: Alphasatellites

no particles of their own
no particles of their own

Contents

General Description

Satellites are sub-viral agents composed of nucleic acid molecules that depend for their replication on co-infection of a host cell with a specific helper virus. Nucleotide sequences are substantially distinct from those of the genomes of the helper virus and of the host. Replication of the helper virus is often decreased and virus symptoms may be modified.

Satellite nucleic acids consist of those satellites that do not encode their own coat protein (unlike satellite viruses) but are encapsidated in that of the helper virus. Particles containing satellite nucleic acid are therefore antigenically identical to those of the helper virus but can sometimes be distinguished by physical features such as sedimentation rates.

All known single stranded satellite DNAs are associated with plant viruses. Alphasatellites were first discovered in association with begomoviruses (where they were initially described as DNA-1 molecules). They encode a rolling-circle replication initiator protein (Rep) and are capable of self-replication in an appropriate host but depend upon the helper virus for encapsidation and movement between plants. They are related to the Rep proteins of nanoviruses, the genomes of which often have additional satellite like DNAs that are also grouped here as alphasatellites.

Morphology

There are no distinctive virions because they are encapsidated in the coat protein of their helper virus.

Genomen

Monopartite, circular, ssDNA of 1000-1400nt.

Genera in the Family

Satellites are not formally classified into families, genera and species but logically group as follows: