Flu life cycle

Question 1

Dominant H1N5 strain in N. America

Answer 1

B3.13

Question 2

Concern of spread of dominant strain of H15N

Answer 2

Cattle human interaction

Question 3

What do influenza virus A infect

Answer 3

Humans, pigs, birds, horses, aquatic mammals

Question 4

Which type of infleunza virus causes global pandemics

Answer 4

Type A

Question 5

Influenza B infects what host

Answer 5

Humans

Question 6

Influenza virus C infects what host

Answer 6

Human and pig

Question 7

Infleunza virus D infects what host

Answer 7

Humans and pigs

Question 8

Describe morphology of influenza virus

Answer 8

Pleomorphic virus particles
Occasional rod-shaped elongated particles
Three membrane proteins, Na, H2 and M2

Question 9

M1 lies where in the virion

Answer 9

Inside

Question 10

M2 lies where on the virion

Answer 10

Membrane channel

Question 11

M2 is ___amer

Answer 11

Tetramer

Question 12

NA is a ___mer

Answer 12

Tetramer

Question 13

HA is a ___mer

Answer 13

Trimer

Question 14

Is influenza negative or positive sense

Answer 14

Negative

Question 15

Are the 8 segments linear or circular

Answer 15

Linear

Question 16

What complexes are the segments assembled into

Answer 16

RNA-protein complexes called RNPs

Question 17

What do the strands of influenza look like in the virus particle

Answer 17

Hairpins

Question 18

What are the flu RNA strands held together by what two interactions

Answer 18

1. Canonical Watson-Crick interactions forming between 5’ and 3’ nt, these are complementary.
2. 5’ and3’ ends interact with a complex of three proteins called RdRp.

Question 19

What viral proteins covers the RNA forming a chain and involved in forming RNPs

Answer 19

Nucleoprotein NP

Question 20

Chain formation of NP requires on two properties

Answer 20

• NP-NP interaction via the tail loop (tail loop of NP interacts with an adjacent NP)
• RNA binding within a groove on the NP surface which is lined with +ve charged a.a such as lys and arg. Electrostatic interaction to the backbone.

Question 21

Influenza virus RNPs are further folded into what configuration, what holds these strands

Answer 21

Double RNA helices, they are antiparallel held together by NP-NP interactions

Question 22

What makes up the RdRp of infleunza

Answer 22

PB1, PB2 and PA

Question 23

What two genes are spliced

Answer 23

M into M2 and NS into NS2/NEP

Question 24

NS1 function

Answer 24

Non-structural protein 1: IFN antagonist, RNP export

Question 25

Ns2/NEP function

Answer 25

Non structural protein 2: RNA export (spliced)

Question 26

M1 function

Answer 26

Matrix protein

Question 27

M2 function

Answer 27

Ion channel

Question 28

Are some additional protein products made during infection, what abundance

Answer 28

Yes, low abundance

Question 29

Describe the 8 steps of the influenza life cycle

Answer 29

1. Virus binds SA receptor via HA, interanlisation 2. Low pH induced membrane fusion via Ha 3. Segments released into cytoplasm 4. Segments imported into nucleus 5. RNA synthesis 6. RNA/RNP export 7. Virus assembly at plasma membrane 8. Release

Question 30

Virus attatchment is mediated by what protein

Answer 30

HA

Question 31

Sialic acid is present on what cells

Answer 31

Epithelial cells, especially ciliated epithelial cells, mainly found in LTR also URT

Question 32

Sialic acid is linked to galactose in what two ways

Answer 32

alpha2-3 or alpha2-6 linkages

Question 33

The infectivity of cells is dependent on what linkage

Answer 33

Sialic acid

Question 34

Human infleunza viruses mainly infect cells which what type of SA linkage

Answer 34

Alpha 2-6

Question 35

Avian influenza viruses mainly infect cells with what SA linkage

Answer 35

Alpha2-3

Question 36

Describe structure and formation of HA

Answer 36

Initially synthesised as HA0 Assembled into trimer HA0 cleaved --> HA1, HA2 Ha1 forms globular head, receptor binding HA2 forms long stalk via 6 helix bunle

Question 37

Cleavage of HA0 is mediated by what

Answer 37

Cellular proteases

Question 38

After binding SA is internalised into what structure

Answer 38

Endosome

Question 39

What does fusion allow for

Answer 39

RNP segments to be released

Question 40

HA contains what peptide

Answer 40

Fusion peptide

Question 41

Inside the endosome due to low pH what conformational change is triggered

Answer 41

two helices in HA2 become aligned this flips the fusion peptide upwards and so the fusion peptide inserts itself into the endosome membrane. Further pH-induced changes brings the 2 membranes together.

Question 42

HA two functions in life cycle

Answer 42

Virus attatchment Virus entry

Question 43

RNP release is mediated by what protein, how

Answer 43

M2, influx of H+/K+ ions so matrix later breaks down

Question 44

Where does RNA synthesis occurs

Answer 44

Nucleus

Question 45

RNPs are too big to diffuse into the nucleus, how are they imported

Answer 45

there is an active transport process for RNP import. Individual NP monomers have 2 import signals, only NLS1 is exposed on formed RNPs. NLS1 recruits importin-alpha, which recruits importin-beta. RNP/importin complex binds pore and enters nucleus.

Question 46

What two processes is RNA synthesis split into

Answer 46

Transcription and replication

Question 47

Describe infleunza virus polymerase interactions with host factors

Answer 47

PB2 interacts with ANP32 to form an asymmetric dimer, the interaction is necessary for polymerase activity.

Question 48

Describe 4 stages of transcription

Answer 48

1. RdRp PB2 binds a cellular mRNA in the nucleus and PA steals its 5’ cap 2. RdRp and capped oligonucleotide bind to negative stranded RNA genome 3. RdRp PB1 uses the capped RNA to begin transcription, gets incorporated 4. RdRp moves along template, PB1 generates a RNA transcript with a 5’ cap and a 3’ poly (A) tail – mRNA is not encapsidated

Question 49

Does transcription or replication occur first

Answer 49

Transcription

Question 50

Describe process of replication, 4 steps

Answer 50

1.RdRp binds 3’ end of the RNA segment, no primer needed 2. RdRp travels along the segment 3’ to 5’ generating a complimentary copy 3. NP wraps the RNA as it is made – so replication products are RNPs 4. Cycles of replication allow amplification of genomes

Question 51

Why does transcription occur first

Answer 51

NP is needed for replication

Question 52

RNA export involves the binding of _____ and _____

Answer 52

Involves binding of M1 and NS2/NEP

Question 53

In RNA export what do RNPs associate with

Answer 53

Multiple copies of M1

Question 54

Do all RNP associated proteins have import signals

Answer 54

Yes

Question 55

NS2 binds M forming _______, and why

Answer 55

Outer layer on RNP; has an export singal which dominates all other signals

Question 56

What is RNP export mediated by C_____

Answer 56

This is mediated via a protein called CRM1 which binds Ran-GTP and exist NPC.

Question 57

All 8RNPs much reach the a_____ surface membrane, alongisde the 4 strucutral proteins

Answer 57

Apical

Question 58

In the cytoplasm are the mRNAs translated and they move down what pathway

Answer 58

The mRNAs are translated in the ER then the proteins are trafficked via secretory pathway.

Question 59

The location of the 8 segments of RNPs follows what arragement X+Y

Answer 59

7+1

Question 60

Virion formation involves the plasma membrane doing what;

Answer 60

Virion formation involved curving the PM around the 8 RNP segments.

Question 61

Curvature of the plasma membrane is due to...

Answer 61

Curvature is caused by combination event of HA, NA, M1

Question 62

Pinching off involves depolorisation of the membrane, what protein directs this

Answer 62

M2

Question 63

Does influenza use ESCRT

Answer 63

NO

Question 64

Function of NA

Answer 64

Cleaves sialic acid on previously infected cell, allowing further infection