Hijacking

Question 1

Which viruses encode dUTPases

Answer 1

Herpes

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Question 2

Which viruses encode TK?

Answer 2

Herpes and pox

Question 3

Which viruses encode ribonucleotide reductases

Answer 3

Herpes and pox viruses

Question 4

Which viruses encode UNG?

Answer 4

Herpes and pox

Question 5

Which viruses hijack cellular UNG?

Answer 5

HIV incorporates for latency

Question 6

What does APOBEC3G do?

Answer 6

Cytosine deaminase to uracil.

Question 7

How does APOBEC3G damage viruses?

Answer 7

C-U replicated as G-A on other strand so is misreplicated or UNG degraded by base excision

Question 8

How does HIV combat APOBEC3G?

Answer 8

Vif excludes from particles

Question 9

What does ADAR do?

Answer 9

A-I deamination then I-C base pair in replication immortalised as G. I-U in transcription.

Question 10

How do ADAR mutations affect the cell?

Answer 10

Mutation or removal and repair or translation

Question 11

The two main ways viruses change protein synthesis?

Answer 11

Decrease cellular translation

Increase viral translation

Question 12

What are the 3 methods to increase viral translation?

Answer 12

IRES target to ribosome directly
VpG cap analogues
Cap snatching

Question 13

What are the 6 methods to decrease cellular translation?

Answer 13

Cleave eIF4G
Bind eIF4G
Cleave PABP
Degrade host mRNA 
Cap snatching 
Prevent 4EBP release 
Prevent regeneration of eIF2 GTP

Question 14

Which viruses target eIF4G?

Answer 14

HIV proteases
Flu NS1 binds
Rotavirus nsp3 stops association with PABP

Question 15

Which viruses cleave PABP?

Answer 15

FMDV

lentiviruses

Question 16

Which virus degrades host mRNA?

Answer 16

Herpes vhs protein endonuclease binds eIF4A

Question 17

Which viruses use cap snatching?

Answer 17

Influenza

Vaccinia

Question 18

How does PABP dissociation or cleavage reduce translation?

Answer 18

No looping of ribosome back to start

Question 19

How does HSV inhibit translation?

Answer 19

Blocks TSC to prevent 4EBP PP to release eIF4E for mnk1 phosphorylation

Question 20

Which viruses prevent 4EBP to inhibit eIF4E phosphorylation?

Answer 20

HCV HIV - increase PI3K
HCMV HPV(E6) HSC - block TSC

Question 21

How is eIF2 GTP regeneration blocked?

Answer 21

PKR phosphorylates eIF2 alpha 51Ser. Results in sequestering of eIF2B GEF.

Question 22

How do viruses inhibit eIF2 regeneration?

Answer 22

Polio degrades PKR
Flu NS1 sequesters dsDNA
Flu NS1 directly binds PKR
HCV NS5a blocks dimerisation

Question 23

How does PERK control translation?

Answer 23

Phosphorylates eIF2

Question 24

What activity does the vhs protein of HSV have?

Answer 24

Endonuclease cleaves host mRNA for degradation

Cleaves eIF4G for cap snatching of C terminal

Question 25

How is 4EBP1 activated?

Answer 25

RTK- PI3K - Akt
Blocks TSC degradation of Rheb GTP to GDP
Rheb GTP activates mTORC1 
Diphos of 4EBP1 releases eIF4E 
Mnk1 phosphorylates

Question 26

How does an IRES cause translation?

Answer 26

Internal ribosome entry site directly binds ribosome with reduced requirement for initiation factors

Question 27

What is the IRES structure?

Answer 27

Stem loops with pseudoknots

Question 28

What type of viruses encode VpG?

Answer 28

+ssRNA viruses

e.g. Norovirus

Question 29

How does VpG work?

Answer 29

Binds eIF4G and eIF3 to recruit 43S ribosome

Translation starts 10nt from 5’ end with no scanning

Question 30

What are the 2 cap independent translation mechanisms?

Answer 30

VpG analogues

Bind via 3’ RNA without P(A)