You are currently reviewing an older revision of this page.
Cyclovirus genomes contain two major ORFs encoding the Rep and Cp. In contrast to members of the genus Circovirus, cycloviruses have the putative ori on the Cp-encoding strand [{Rosario et al., 2012:22760663RJOHTXRosario et al., 2012, A field guide to eukaryotic circular single-stranded DNA viruses: insights gained from metagenomics, Archives of Virology, 157, 10, 1851-71}]. In addition, cyclovirus genomes have an IR between the 5' end of major ORFs; however, the IR between the 3' ends of these ORFs is smaller than that of genomes representing the genus Circovirus or may be absent [{Li et al., 2010:20007276RJOHTXLi et al., 2010, Multiple diverse circoviruses infect farm animals and are commonly found in human and chimpanzee ***, Journal of Virology, 84, 4, 1674-82RJOMREFDelwart and Li 2012:22155583RJOHTXDelwart and Li 2012, Rapidly expanding genetic diversity and host range of the Circoviridae viral family and other Rep encoding small circular ssDNA genomes, Virus Research, 164, 1-2, 114-21}]. Introns have been identified within the ORFs of several cyclovirus genomes, while none have been reported for circoviruses.
Unknown.
Cycloviruses exhibit small, circular ssDNA genomes ranging approximately from 1.7 to 1.9 kb.
Cyclovirus genomes contain two major ORFs encoding the Rep and Cp [{Rosario et al., 2017:28155197RJOHTXRosario et al., 2017, Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus, Archives of Virology, 162, 5, 1447-63}]. Although the virion strand has not be experimentally demonstrated for cycloviruses, knowledge from other eukaryotic Rep-encoding ssDNA viruses suggests that the strand containing the nonanucleotide motif is encapsidated [{Rosario et al., 2012:22760663RJOHTXRosario et al., 2012, A field guide to eukaryotic circular single-stranded DNA viruses: insights gained from metagenomics, Archives of Virology, 157, 10, 1851-71}]. Since the putative cyclovirus ori and predicted Rep share conserved features with members of the genus Circovirus, cycloviruses are also thought to replicate through RCR. Similar to circoviruses, the putative cyclovirus ori contains the canonical nonanucleotide motif ‘NAGTATTAC’ located at the apex of a potential stem-loop structure found between the 5’ ends of major ORFs. In addition, the Rep contains endonuclease and helicase domains with RCR and SF3 motifs similar to those identified in circovirus Reps. These conserved motifs include RCR motifs I [FT(L/W)NN], II [(P/x)HLQG] and III [Y(C/l)(S/x)K] and SF3 helicase motifs Walker-A [G(P/x)(P/t)(G/x)xGKS], Walker-B [uuDDF], and motif C [uTS(N/e)], where ‘‘x’’ represents any type of residue and ‘‘u’’ represents a hydrophobic amino acid (i.e., F, I, L, V, M). Moreover, putative Rep-binding domains characterized by iterative sequences near the stem-loop structure have been identified for some cyclovirus genomes [{Dayaram et al., 2013:23596268RJOHTXDayaram et al., 2013, High global diversity of cycloviruses amongst dragonflies, Journal of General Virology, 94, Pt 8, 1827-40}].
Cyclovirus genomes were originally discovered in primate stool samples and meat products from diverse animals (camels, chickens, cows, goats, sheep) [{Li et al., 2010:20007276RJOHTXLi et al., 2010, Multiple diverse circoviruses infect farm animals and are commonly found in human and chimpanzee ***, Journal of Virology, 84, 4, 1674-82RJOMREFDelwart and Li 2012:22155583RJOHTXDelwart and Li 2012, Rapidly expanding genetic diversity and host range of the Circoviridae viral family and other Rep encoding small circular ssDNA genomes, Virus Research, 164, 1-2, 114-21}]. However, cyclovirus genomes have now been reported from various types of human samples other than faeces, including cerebrospinal fluid, blood serum, and respiratory secretions [{Smits et al., 2013:23968557RJOHTXSmits et al., 2013, Novel cyclovirus in human cerebrospinal fluid, Malawi, 2010-2011, Emerging Infectious Diseases, 19, 9RJOMREFTan le et al., 2013:23781068RJOHTXTan le et al., 2013, Identification of a new cyclovirus in cerebrospinal fluid of patients with acute central nervous system infections, MBio, 4, 3, e00231-13RJOMREFPhan et al., 2014:24421114RJOHTXPhan et al., 2014, Cyclovirus in nasopharyngeal aspirates of Chilean children with respiratory infections, Journal of General Virology, 95, Pt 4, 922-7RJOMREFPhan et al., 2015:25839169RJOHTXPhan et al., 2015, Small circular single stranded DNA viral genomes in unexplained cases of human encephalitis, diarrhea, and in untreated sewage, Virology, 482, 98-104}]. Additionally, cycloviruses have been detected in sampled from a wide range of mammalian and insect species [{Rosario et al., 2017:28155197RJOHTXRosario et al., 2017, Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus, Archives of Virology, 162, 5, 1447-63}]. Since genomes belonging to the genus Cyclovirus have only been identified through sequence-based analyses (i.e., degenerate PCR and metagenomic sequencing), definitive hosts and biology are largely unknown.
The species demarcation threshold is 80% genome-wide nucleotide sequence identity based on pairwise identity distribution analysis (Figure 3.Circovirus) [{Rosario et al., 2017:28155197RJOHTXRosario et al., 2017, Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus, Archives of Virology, 162, 5, 1447-63}].
Cyclo: indicates circle or ring in Greek.