Leishmaniavirus (taxid:39755)

VIRION

Non enveloped, icosahedral virion composed of a single capsid protein (CP), about 33 nm in diameter. The capsid has a T=2* icosahedral symmetry.

GENOME

Linear dsRNA genome of 5.3 kb. The genome has two large, overlapping ORFs on the positive strand respectively encoding CP and RdRp, and a small 5'-proximal potential ORF.

GENE EXPRESSION

The dsRNA genome is never completely uncoated, to prevent activation of antiviral state by the cell in response to dsRNA. The viral polymerase synthesizes a mRNA, which is translocated to the cell cytoplasm where it is translated.
Translation is initiated on a unique internal ribosome entry site (IRES) element situated at the 5'-UTR.
L-A virus seems to furnish its transcript with a cap structure derived from host mRNAs by cap snatching . m(7)Gp from the cap donor is transferred to the 5' end of the viral transcript, thus preserving the 5' α-and β-phosphates of the transcript in the triphosphate linkage of the final product. The plus-strand viral transcript directs the translation of the major CP (Gag) and the minor fusion protein CP-RdRP (Gag-Pol) via a -1 ribosomal frameshift.

ENZYMES

• RNA-dependent RNA polymerase [POL]
• Toti-type cap snatching [Capsid]

REPLICATION

CYTOPLASMIC

1. Virus remains intracellular.
2. 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.
3. (+)RNAs are encapsidated in a sub-viral particle, in which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
4. Mature virions may be transmitted to new cells during cell division.