Norovirus

VIRION

Non-enveloped, capsid of about 38-40 nm in diameter, with T=3 icosahedral symmetry. The capsid is composed of 180 VP1 proteins. Small empty virions are about 23nm in diameter, and would be of T=1 icosahedral symmetry, composed of 60 VP1 proteins.

GENOME

Monopartite, linear ssRNA(+) genome of 7.3 to 8.3 kb. The 5’-terminus is linked to a VPg protein and the 3’-terminus has a poly(A) tract.n (VPg)is covalently linked to genome, whereas 3’-terminus is polyadenylated.

GENE EXPRESSION

The virion RNA is infectious and serves as both genome and viral messenger RNA. Cleavage of ORF1 polyprotein by the virus-encoded 3C-like cysteine proteinase yields the mature nonstructural proteins. Subgenomic RNA encodes the capsid protein and VP2 minor structural protein which is expressed through RNA termination-reinitiation. Murine norovirus express an alternative ORF from the CP mRNA by leaky scanning.

REPLICATION

CYTOPLASMIC

  1. Attachement to host receptors mediates clathrin- and caveolin-independent endocytosis of the virus.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
  3. VPg is removed from the viral RNA, which is then translated into a processed ORF1 polyprotein to yield the replication proteins.
  4. Replication occurs in 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. Subgenomic RNA translation gives rise to the capsid protein and VP2.
  7. Assembly of new virus particles and release by cell lysis.

Host-virus interaction

Apoptosis modulation

Murine norovirus induces host cell apoptosis .

Host gene expression shutoff by virus

Noroviruses mediate host translation shutoff by cleaving PABP1 .

Matching UniProtKB/Swiss-Prot entries

9 entries grouped by strain (browse by keywords)

3 entries

Norwalk virus (strain GI/Human/United States/Norwalk/1968) (Hu/NV/NV/1968/US) reference strain

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CAPSD_NVN68Capsid protein VP1 (CP) (p59)
POLG_NVN68Genome polyprotein
VP2_NVN68Protein VP2 (Minor capsid protein)

3 entries

Lordsdale virus (strain GII/Human/United Kingdom/Lordsdale/1993) (Human enteric calicivirus) (Hu/NV/LD/1993/UK)

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CAPSD_LORDVCapsid protein (CP) (VP1)
POLG_LORDVGenome polyprotein
VP2_LORDVProtein VP2 (Minor capsid protein)

3 entries

Southampton virus (strain GI/Human/United Kingdom/Southampton/1991) (SHV) (Hu/NV/SHV/1991/UK)

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CAPSD_SOUV3Capsid protein VP1 (CP)
POLG_SOUV3Genome polyprotein
VP2_SOUV3Protein VP2 (Minor capsid protein)