Chapter 13: Reoviruses and other dsRNA Flashcards
Reoviridae
Respiratory
Enteric
Orphan (“no” disease association)
Reoviridae Virion
- Spherical (icosahedral symmetry)
- 60-80 nm in diameter
- Genome: dsRNA, 10~20 segments, 18~32 kbp
- Usually naked
Rotavirus
“wheel” in Latin
Rotavirus Virion
Spherical, wheel like
Icosahedral symmetry
75 nm in diameter
Triple layer particle
Triple Layered Particle
Inner layer made of VP2
Middle layer made of VP6, contain “spokes” of the wheel
Outer layer made of VP7 (glycoprotein)
VP1
RNA polymerase
VP3
capping enzyme
Rotavirus Genome
11 dsRNA segments, 22 kbp
(+) strands are all capped
No poly A
12 gene products
Each segment in Rotavirus genome
Associated with VP1 and VP3
Has unique sequence for assembly
Has 1 ORF except that RNA 11 has 2 ORFs in different reading frames
Rotavirus Attachment
Many details unclear
Cleavage of Spike protein VP4
Spike proteins and capsid glycoprotein interact with cell surface proteins
Cleavage of VP4
Into VP8* and VP5* by trypsin
Rotavirus Entry
Direct penetration (mediate by hydrophobic VP5*) or endocytosis
Rotavirus Entry Events
Remove outer layer
Early transcription inside double-layered particle
Translation and modification
NSP2 and NSP5 assemble viroplasm
VP1, VP3 bind to (+) RNA, then to VP2 -> form core
(-) RNA synthesis inside core
VP6 attach core -> double layer particle
Viroplasm
viral protein accumulating region for viral replication/assembly
Rotavirus Late Events
Late transcription inside double-layered particles -> late mRNA not capped
Cell translation machinery changes
NSP4 and VP7 synthesized in rough ER
Virus controls the quantity of each of 12 viral proteins produced
NSP4 binds VP4 and double-layered particles
The complex buds through ER into a vesicle
VP7 cleaved from vesicle membrane -> build outer layer
VP4- form spikes
Virions released via cell lysis