CSB351Y1 Lecture Notes - Lecture 37: Reoviridae, Open Reading Frame, Ependyma
26 May 2018
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Lecture 37: Reovirus
• Respiratory, enteric, orphan -
- Gives both sneezing and coughing illness, diarrhea and gastric problems, not much symptoms involved
• Double-shelled icosahedral capsids, Segmented dsRNA genomes, 60-80nm in diameter
• Mammalian reoviruses have 10 genomic segments and all share common complement fixing antigen
• All members of the family have dsRNA genomes consisting of 10,11 or 12 segments
Distinctive characteristics
• Virion – found outside the cell
• Infectious subvirial particle (ISVP) – virions that undergo partial degradation by cathepsins found in endosomes
- Disassembly viewed using cryoelectron microscopy
- Spike protein very much exposed
- Core – found when virus is replicating (No spike protein, RNA synthesis)
Virion structure
• σ3 (outer coat protein of virion)
• σ1 (receptor binding spike protein), Λ2 (role in replication), μ1 (inner capsid protein, virion shell)
- inner capsid T=2 and outer capsid T= 13 (for more complex)
• Have channels/pentameric turrets (channels) in the innermost capsids (channels with spike protein sticking out)
- Spike protein (σ1) sticks out of core at each 12 vertices of core icosahedron
• Virions are not enveloped – 2 layers, 1 layer lost later
Genome
• L (large) – encodes proteins designated Λ
• M (medium) – encodes proteins designated u
• S (small) – encodes proteins designated σ
• No polyA trat 3’ ut ethylated uleotide ap 5’ o positive strad egative strad have phosphorylated
terminus)
• 23.5kb, each having single open reading frame on RNA segments
Reovirus life cycle
1. Uncoat as virion enters into host
- Enter through endocytosis OR directly enter cell (ISVP)
- Lysosome remove outer capsid of virion (just core left)
- Spike protein has been removed
2. Primary transciprtion of dsRNA into mRNA (+sense)
- -sense used as template to make +sense
- Leave core virus particle and become capped, translated into proteins by cellular ribosomes
- Viral factory becomes produced (virus replication and assembly)
3. New core assembly (RNA sensitive)
- Loosely put together
4. Minus strand synthesis
- After capped transcripts enter into new core, +sense mRNAs synthesized to –sense dsRNA
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Document Summary
Lecture 37: reovirus: respiratory, enteric, orphan - Distinctive characteristics: virion found outside the cell. Infectious subvirial particle (isvp) virions that undergo partial degradation by cathepsins found in endosomes. Core found when virus is replicating (no spike protein, rna synthesis) Spike protein ( 1) sticks out of core at each 12 vertices of core icosahedron: virions are not enveloped 2 layers, 1 layer lost later. L (large) encodes proteins designated : m (medium) encodes proteins designated u, s (small) encodes proteins designated . No polya tra(cid:272)t (cid:894)3"(cid:895) (cid:271)ut (cid:373)ethylated (cid:374)u(cid:272)leotide (cid:272)ap (cid:894)5"(cid:895) o(cid:374) positive stra(cid:374)d (cid:894)(cid:374)egative stra(cid:374)d have phosphorylated terminus: 23. 5kb, each having single open reading frame on rna segments. Reovirus life cycle: uncoat as virion enters into host. Enter through endocytosis or directly enter cell (isvp) Lysosome remove outer capsid of virion (just core left) Spike protein has been removed: primary transciprtion of dsrna into mrna (+sense) Leave core virus particle and become capped, translated into proteins by cellular ribosomes.
