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MICR2222 - Medical Virology > L1/2 - Influenza > Flashcards

L1/2 - Influenza Flashcards

(49 cards)

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1
Q

Which influenza viruses have 8 segments?

A

A

B

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2
Q

Which influenza viruses have 7 segments

A

C

D

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3
Q

What are the 3 membrane proteins of influenza?

A

NA
HA
M2

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4
Q

Why do the segments not look like linear strands of DNA?

A

segments are wrapped up in RNA interactions and RNA-protein interactions

RNA-PROTEIN COMPLEXES

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5
Q

What are the two interactions that hold the RNA segment ends together

A

Watson-Crick interactions

PAN HANDLE STRUCTURE

5’ and 3’ ends interacts with RdRp

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6
Q

What protein does the RNA molecule interacts with?

A

NP - entirely covers

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7
Q

What 2 properties of NP

A

RNA binding via pos-charged residues in groove

NP-NP interaction via tail loop

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8
Q

What kind of conformation do influenza RNPs adopt?

A

hairpin

double helical conformation

antiparallel

held by NP-NP interactions

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9
Q

What 3 segments make the RdRp

A

PB1
PB2
PA

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10
Q

How can the 8 segments of influenza achieve more coding potential?

A

splicing

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11
Q

What is the 1st stage of the influenza virus life cycle?

A

virus attachment

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12
Q

How does virus attachment take place in influenza

A

mediated by HA

sialic acid recognised

target epithelial cells

virus internalised within endosome

different types of sialic acid linkage

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13
Q

Why does the Human and avian flu have different sialic acid linkages?

A

HA proteins show specificity to just one SA type

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14
Q

What sialic acid linkages does human influenza infect?

A

a2-6

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15
Q

What sialic acid linkages does avian influenza infect?

A

a2-3

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16
Q

How can specificity of sialic acid binding be switched?

A

single residue changes

e.g. Glu90

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17
Q

How does flu fuse with endosomes

A

pH 5 - mediates conformational shift in the HA protein

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18
Q

What is stage 2 of the influenza life cycle?

A

virus entry

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19
Q

How does the influenza virus escape the endosome?

A

fusion of viral & endosomal membranes

RNP segments released

mediated by HA protein and fusion peptide

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20
Q

How does the fusion peptide allow fusion to occur?

Study These Flashcards
A

fusion peptide buried in HA0

HA1/HA2 cleavage = repositioning at amino-terminus

sticks into endosomal membrane

21
Q

What is the conformation change that happens to the fusion peptide?

Study These Flashcards
A

2 helices in HA2 align

flips fusion peptide upwards

insertion

22
Q

what are the 2 CRITICAL FUNCTIONS of the HA protein?

Study These Flashcards
A

1) virus attachment via sialic acid

2) virus entry by fusion of viral & endosomal membranes

23
Q

What is the 3rd stage of the influenza life cycle?

24
Q

What happens during RNP release from matrix proteins?

Study These Flashcards
A

mediated by M2

M2 x 4 = tetramer

M2 - influx of H+ ions into virion

25
What is the 4th stage of the influenza life cycle?
RNP import
26
What happens during RNP import
move from cytoplasm to nucleus individual NP monomers - 2 import signals
27
what is the ONLY NLS exposed on formed RNPs?
NLS1 recruits importin alpha recruits importin b RNP/importin complex binds pore and enters
28
What is the 5th stage of the influenza life cycle?
RNA synthesis
29
what are the 2 processes of RNA synthesis?
Transcription | Replication
30
What is the polymerase structure for influenza?
3 subunits | 4 holes lead to centre of the polymerase
31
What happens during influenza transcription
results in 1 RNA transcript PER SEGMENT resemble cellular mRNAs
32
What are the 4 stage of influenza transcription?
RdRp PB2 binds cellular mRNA in nucleus - PA steals 5' cap RdRP + capped oligonucleotide bind to negative RNA genome RdRP PB1 - use capped RNA, transcription RdRp - move along templated, PB1 generates RNA transcript with polyA tail & 5' cap (NOT ENCAPSIDATED)
33
What is the fate of influenza mRNA?
some stay in cytoplasm some exported through nuclear pores - translated to viral proteins
34
How are some influenza proteins imported back into the nucleus?
imported by NLS
35
How can NS2 protein get back inside with nucleus without NLS?
it is an export signal - cannot have import very small
36
What are the 4 stages of influenza replication
RdRP binds 3' end of RNA segment (no primer) RdRp travels along segment - 3' to 5' direction - complimentary copy NP wraps RNA = RNPs cycles = amplification of genomes
37
Why does transcription have to occur before replication in influenza?
requirement for NP
38
What is the 6th stage of the influenza life cycle?
RNP export
39
What is involved in RNP export (influenza)?
binding of M1 and NS2 - RNPs associated with M1 in nucleus - NS2 binding M forming outer layer on RNP - NS2 has export signal, dominant over other signal - NS2 covers NLS - CRM1 binds to NS2 and helps export
40
What protein, along with NS2, mediates RNP export in influenza?
CRM1 binds Ran-GTP exits through NPC
41
Where must RNPs reach?
the apical surface - with the 3 envelope proteins
42
How do RNPs traffic by recycling endosomes?
interactions of RNPs with Rab11 M1 associates with cytoplasmic tails of the 3 envelope proteins
43
What is another name for M1?
MASTER RECRUITER
44
Why is viral release polarised towards apical surface and not the basolateral surface?
recycling endosomes only move to the apical surface
45
What is the 7th stage of the influenza life cycle?
virus assembly
46
What happens during virus assembly of influenza?
segments are selected 7+1 arrangement
47
What is evidence for direct RNP interactions in virions between segments?
segments interact via RNA-RNA interactions multiple interactions allow for sequence variations without impaired packaging e.g. PB1-NP interaction
48
What is the 8the stage of the influenza virus life cycle?
virus release
49
What happens during influenza virus release?
NA solves the issue of binding on the sialic acid of the old cell NA cleaves sialic acid from previously infected cell - only new ones infected

MICR2222 - Medical Virology (13 decks)

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