Poliovirus

Question 1

Poliovirus

Answer 1

+ssRNA virus from picornavirus family

Question 2

Baltimore system

Answer 2

virus classification system based on genome structure

Question 3

Polio route of infection

Answer 3

oral-faecal/respiratory

Question 4

Difference between virus and virion

Answer 4

Virus is nucleoprotein particle whereas virion is active extracellular vector of virus

Question 5

Polio virion

Answer 5

30nm diameter
+ssRNA

Question 6

VPg protein

Answer 6

Covalently attached to 5’UTR of RNA
Act as primer for RNA synthsis or tag
Protein 3B

Question 7

P1 protein

Answer 7

Capsid structure

Question 8

Capsid functions

Answer 8

Packaging (RNA protection)
Cell entry (1. receptor binding, entry mechanism
Immune evasion

Question 9

Capsid proteins

Answer 9

VP0, VP3, VP1

Question 10

VP0

Answer 10

VP2 + VP4 after cleavage of VP0 for maturation
VP4 myrostylated at N terminus to penetrate cell membrane

Question 11

Myristylation

Answer 11

14-carbon unsaturated fatty acid, myristic acid, added to the N-terminal glycine of a subset of proteins

Question 12

Poliovirus pocket factor

Answer 12

lipid base center of capsid proteins - capsid falls apart without it

Question 13

1 pentamer (polio)

Answer 13

Made up of 5 protomers

Question 14

1 Capsid (polio)

Answer 14

12 pentamers

Question 15

Poliovirus receptor and where are they located?

Answer 15

CD155
3 ig-like domains
located on motor neurons, lymph nodes and ileum wall cells

Question 16

What happens when PV binds to receptor?

Answer 16

Structual change of VP1 induced
Pocket factor released
Destabilisation of capsid

Question 17

How is PV delivered into the cytoplasm?

Answer 17

VP1 n terminus externalised and forms pore in host cell membrane
RNA delivered through pore by dynamin dependent caveolar endocytosis

Question 18

Poliovirus A particle

Answer 18

Capsid destabilised and VP4 disassociated from protomers

Question 19

Internal ribosome entry site structure and function

Answer 19

dsRNA in 5’ UTR of PV genome
6 dsRNA structures with first being cloverleaf involved in translation initiation
binds directly to 40S rsubunit
cap not needed
uses eIF4G fragment
AUG placed in correct position for initiation

Question 20

eIF4G

Answer 20

part of F cap binding complex
strongly associates with E
cleaved by viral proteases

Question 21

Why translation of PV ssRNA before replication

Answer 21

To synthesise P2 and P3 proteins needed for replication

Question 22

PV replication initiation complex (1st)

Answer 22

3CD + polyC binding protein + polyA binding protein
located on 5’ cloverleaf structure
lowers translation efficiency

Question 23

PolyC binding protein

Answer 23

Required for replication
translational silencing
when 3CDpro binds this increases affinity for PCbp binding

Question 24

PolyA binding protein

Answer 24

Binds to cloverleaf structure and circularises RNA

Question 25

CRE (PV) (2nd complex) steps

Answer 25

cis acting replication element
3Dpol + VPg + 3CD
formed on circularised RNA

Question 26

Replicative form (PV)

Answer 26

positive and negative RNA strands associated together w VPg at 5’ ends

Question 27

Protein 2C

Answer 27

Helicase of replicative form

Question 28

Steps in poliovirus replication

Answer 28

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