Polyomaviridae. Polyomaviridae

Description of Polyomaviridae adapted from ICTVdb Virion Properties Morphology Virions consist of a capsid. Virus capsid is not enveloped, round with icosahedral symmetry (T=7). The capsid is isometric and has a diameter of 40-55 nm. Capsids appear round. The capsomer arrangement is clearly visible. The capsid consists of 72 capsomers (, each of which is composed of five copies of VP1 in skew arrangement). Surface projections are small and surface appears rough. Capsids can be penetrated by stain and some appear dark in the center. Morphologically aberrant forms are observed. They are filamentous or tubular in form as result of aberrant maturation. Physicochemical and Physical Properties Virions have a buoyant density in CsCl of 1.34 g cm-3. Nucleic Acid The Mr of the genome constitutes 10-13% of the virion by weight. The genome is not segmented and contains a single molecule of circular; supercoiled, double-stranded DNA ; that forms a covalently closed circle. The complete genome is 5300-8000 nucleotides long. The genome has a guanine + cytosine content of 40-50 %. Proteins The viral genome encodes structural proteins located in the capsid. Lipids Lipids are absent.