VIRION
Non enveloped, capsid with T=2* icosahedral symmetry, 35-40 nm in diameter 
.
The picobirnavirus crystal structure provides functional insights into virion assembly and cell entry
St?phane Duquerroy, Bruno Da Costa, C?line Henry, Armelle Vigouroux, Sonia Libersou, Jean Lepault, Jorge Navaza, Bernard Delmas, F?lix A. Rey
EMBO J. June 3, 2009; 28: 1655?1665
St?phane Duquerroy, Bruno Da Costa, C?line Henry, Armelle Vigouroux, Sonia Libersou, Jean Lepault, Jorge Navaza, Bernard Delmas, F?lix A. Rey
EMBO J. June 3, 2009; 28: 1655?1665
GENOME
Segmented linear dsRNA genome: 2 segments encode for a total of 3 to 4 proteins. Segments size range from 1.7 to 2.5 kb. Genome total size is about 4 kb.
GENE EXPRESSION
Genomic segment 1 encodes for a polyprotein (ORF1) that self-cleaves to yield the mature coat protein and a large peptide. Also encodes another protein (ORF2).
Genomic segment 2 encodes for the RNA-dependent RNA polymerase.
ENZYMES
- RNA-dependent RNA polymerase [RdRp]
- Self-cleavage, Virion maturation (Peptidase N5) [Capsid precursor]
REPLICATION
CYTOPLASMIC
- Virus penetrates into the cytoplasm.
- Transcription of the dsRNA genome by viral polymerase occurs inside the virion, so that dsRNA is never exposed to the cytoplasm. This plus-strand transcript is used as template for translation.
- (+)RNAs are encapsidated in virion particle, inside which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
- Mature virions are released by budding.