RESUMEN
Novel findings and concepts in the field of virology particularly regarding virosphere and giruses--a group of large nuclear-cytoplasmic deoxyriboviruses are briefly summarized. In the context of novel understanding the major taxonomic features and virus pathogenicity including African swine plague are interpreted.
Asunto(s)
Virus de la Fiebre Porcina Africana/genética , ADN Viral/genética , Iridovirus/genética , Mimiviridae/genética , Picobirnavirus/genética , Fiebre Porcina Africana/virología , Virus de la Fiebre Porcina Africana/ultraestructura , Animales , Cápside/ultraestructura , Núcleo Celular/virología , Citoplasma/virología , ADN Viral/química , Iridovirus/ultraestructura , Mimiviridae/ultraestructura , Picobirnavirus/ultraestructura , PorcinosRESUMEN
Filamentous fungus Fusarium poae is a worldwide cause of the economically important disease Fusarium head blight of cereal grains. The fungus is itself commonly infected with a bisegmented dsRNA virus from the family Partitiviridae. For this study, we determined the structure of partitivirus Fusarium poae virus 1 (FpV1) to a resolution of 5.6Å or better by electron cryomicroscopy and three-dimensional image reconstruction. The main structural features of FpV1 are consistent with those of two other fungal partitiviruses for which high-resolution structures have been recently reported. These shared features include a 120-subunit T=1 capsid comprising 60 quasisymmetrical capsid protein dimers with both shell and protruding domains. Distinguishing features are evident throughout the FpV1 capsid, however, consistent with its more massive subunits and its greater phylogenetic divergence relative to the other two structurally characterized partitiviruses. These results broaden our understanding of conserved and variable elements of fungal partitivirus structure, as well as that of vertebrate picobirnavirus, and support the suggestion that a phylogenetic subcluster of partitiviruses closely related to FpV1 should constitute a separate taxonomic genus.
Asunto(s)
Picobirnavirus/ultraestructura , Cápside/ultraestructura , Microscopía por Crioelectrón , Imagenología Tridimensional , Picobirnavirus/clasificación , Virión/ultraestructuraRESUMEN
Double-stranded (ds) RNA virus particles are organized around a central icosahedral core capsid made of 120 identical subunits. This core capsid is unable to invade cells from outside, and animal dsRNA viruses have acquired surrounding capsid layers that are used to deliver a transcriptionally active core particle across the membrane during cell entry. In contrast, dsRNA viruses infecting primitive eukaryotes have only a simple core capsid, and as a consequence are transmitted only vertically. Here, we report the 3.4 A X-ray structure of a picobirnavirus--an animal dsRNA virus associated with diarrhoea and gastroenteritis in humans. The structure shows a simple core capsid with a distinctive icosahedral arrangement, displaying 60 two-fold symmetric dimers of a coat protein (CP) with a new 3D-fold. We show that, as many non-enveloped animal viruses, CP undergoes an autoproteolytic cleavage, releasing a post-translationally modified peptide that remains associated with nucleic acid within the capsid. Our data also show that picobirnavirus particles are capable of disrupting biological membranes in vitro, indicating that its simple 120-subunits capsid has evolved animal cell invasion properties.
Asunto(s)
Picobirnavirus/química , Picobirnavirus/ultraestructura , Proteínas Virales/química , Virión/química , Virión/ultraestructura , Secuencia de Aminoácidos , Animales , Cápside/química , Cápside/ultraestructura , Proteínas de la Cápside/química , Proteínas de la Cápside/metabolismo , Cristalografía por Rayos X , Dimerización , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Picobirnavirus/fisiología , Procesamiento Proteico-Postraduccional , Virión/fisiología , Internalización del VirusRESUMEN
The prevalence of picobirnaviruses (PBVs) in human stools was investigated by polyacrylamide gel electrophoresis (PAGE) analysis of 832 faecal specimens collected between 1982 and 1993 from patients in various clinical groups. Similar prevalences (9-13%) were detected in patients with or without gastroenteritis and throughout the age range of 3 to > 65 years. Two methods for the extraction of nucleic acid, a phenol/chloroform method and a guanidinium thiocynate (GTC)/silica method, were compared. Detection of PBVs by PAGE was three times more sensitive following RNA extraction by the GTC/silica method. Characterisation of three strains was carried out. Segment sizes ranged from 1.625 to 1.95 kilo base pairs (Kbp) and 2.2 to 2.5 Kbp for the fast and slow migrating bands, respectively. The nuclic acid was shown to be double-stranded RNA (dsRNA) by nuclease digestion. PBV-like particles were detected by electron microscopy in two PAGE-positive stools. Virion diameters ranged from 35 to 41 nm and a buoyant density of 1.38-1.4 g/ml in caesium chloride (CsCl) was demonstrated. These findings suggest that PBVs are widespread in humans in the United Kingdom. However, no disease association could be demonstrated.