Hepeviridae (taxid:3079366)

VIRION

Quasi-enveloped, spherical, about 32-34 nm in diameter. The RNA genome is enclosed within a capsid that is composed of 180 capsid proteins, assembled into a T=3 icosahedral particle . The HEV particles present in feces and bile are non-enveloped, while those in circulating blood and culture supernatants are covered with a cellular membrane, similar to enveloped viruses.

GENOME

Monopartite, linear, ssRNA(+) genome of 7.2 kb. The 5' end is capped and the 3' terminus is polyadenylated. Their is no VPg at the 5'-terminus of the genome. The genome consists of three partially overlapping ORFs.

GENE EXPRESSION

The virion RNA is infectious and serves as both the genome and viral messenger RNA. ORF 1 encodes the nonstructural proteins, it is not clear whether this polyprotein is cleaved or not; ORF 2 encodes the capsid protein; ORF 3 encodes a small immunogenic protein. ORF2 is translated by leaky scanning from the bicistronic ORF3-2 subgenomic RNA.

ENZYMES

• RNA-dependent RNA polymerase [Q81862]
• Polyprotein major protease [Q81862]
• Alpha-type capping [Q81862]

REPLICATION

1. Attachement of the virus to host receptors mediates internalization into the host cell by clathrin-mediated endocytosis.
2. RNA genome is released into the cytoplasm.
3. The positive-sense genomic ssRNA is translated into a processed ORF1 polyprotein to yield the mature non-structural proteins involved in RNA transcription.
4. Replication takes place in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
6. Expression of two other messenger RNAs, a 3.7 kb subgenomic one and a 2.0 kb coterminal one.
7. Virus assembly and release.

Host-virus interaction

Innate immune response inhibition

HEV ORF3 protein suppresses host interferon-α signaling by inhibiting STAT1 phosphorylation .