Poliovirus Flashcards
1
Q
Stages of the Infection Cycle
A
Attachment, Penetration, Uncoating
Gene Expression
Genome Replication
Assembly
Release
Maturation
2
Q
Family
A
Picornaviridae
3
Q
Genus
A
Enterovirus
4
Q
Attachment, Penetration, Uncoating
A
- receptor mediated attachment
- picornavirus particle attaches to host cell via canyon binding to specific host cell receptor
- attachment triggers conformational change in 5 fold vertex causing penetration/uncoating via direct ‘injection’ of (+)ssRNA into host cell cytoplasm
5
Q
Gene Expression
A
- translation
- ribosomes bind to ribosome landing pad
- single ORF encodes a polyprotein
- P1-2A translated. 2A protease co-translationally cleaves to release P1.
- P2-3ABC translated. 3C protease co-translationally cleaves to release P2.
- P3 translated. 3C protease post-translationally cleaves P1, P2, and P3
6
Q
Genome Replication
A
- P3 as 3D RNA polymerase
- takes place on cytoplasmic face of transport vesicles derived from ER membrane
- VPg used as a primer for RNA synthesis
- plus and minus strands synthesized asymmetrically- need more plus than minus strands
- P3 binds to 3’ end of viral RNA -
3D pol copies template and joins first nucleotide to VPg
- joins second nucleotide to first
- 3D pol stalls and must be cleaved in order to elongate
- 3C protease cleaves and 3D pol elongates
- when it reaches 5’ end of template it detaches and RNA synthesis terminates
7
Q
Assembly
A
- P1 folds up into nascent protomer
- protomers combine to form pentamer
- Pentamer binds to VPg-RNA and 11 more come to form provirion (nucleation mechanism)
8
Q
Maturation
A
VP0 cleaved to VP2 and VP4 to form infectious virion
9
Q
Release
A
cell lysis
10
Q
Reprogram Gene Expression
A
- translation of cellular mRNA blocked
- inactivation of cap binding protein by viral protease
- redirects ribosome to viral genome (RLP unaffected)
11
Q
Reprogram Genome Replication
A
- increase number of vesicles derived from ER
- vesicle fusion to cis Golgi inhibited by viral 2B and 3A proteins
- creates more area for replication complexes to bind.
