Notes on Genus: Circovirus


Type member: Porcine circovirus-1


General Description

The genus Circovirus (from the circular conformation of the DNA) is one of two genera in the family Circoviridae and contains viruses with genomes smaller than 2.2kb that are translated from ORFs in both directions.


Virions isometric (icosahedral), not enveloped, 12-21 nm in diameter.


Monopartite circular single-stranded DNA of 1.7-2.2 kb. The origin of replication contains a nonanucleotide sequence TAGTATTAC at the apex of a stem loop.

Genus Genomic Organization

There are two well-characterised ORFs in all the sequenced viruses. A replication protein (V1) of 33-36 kDa is encoded in the virion (positive sense) and a coat protein (C1) of 19-32 kDa in the negative sense. In most members, one or more additional hypothetical ORFs have been identified.

Type Member Genomic Organization

The two well-characterised ORFs are:
  • V1 (+ sense): 35.6 kDa, Replication protein
  • C1 (- sense): 23.7 kDa, Coat protein