Virology Chapter 8

Question 1

How long does the influenza virus replication cycle take

Answer 1

6 hours

Question 2

Where does the replication take place

Answer 2

nucleus

Question 3

does the virus need to pre-package RDRP? If so, why?

Answer 3

Yes, because the host cell’s polymerase cannot read RNA as a template

Question 4

The first step is attachment, H0 is cleaved into…

Answer 4

H1 + H2

Question 5

Using what enzyme

Answer 5

tryptase clara

Question 6

Which one binds to the Sialic acid, H1 or H2?

Answer 6

H1

Question 7

Why do we need this cleavage?

Answer 7

To reveal the fusion peptide in H2

Question 8

What is the fusion peptide for, and where in the H2 protein is it located

Answer 8

allow viral envelope to fuse with the endosome membrane
located on the N terminus

Question 9

After H1 binds to SA, endocytosis happens, then the endosome is acidified, what does that cause

Answer 9

Conformational change in H protein that allows the fusion peptide to be inserted into the endosome membrane, and the viral envelope and endosome membrane fuse together

Question 10

There is also acidification of the interior of the virus particle, caused by what?

Answer 10

Lysosomes

Question 11

H+ then moves through what protein

Answer 11

M2 ion channel

Question 12

H+ entering M2 channel, causing changes in what?

Answer 12

RNP interactions, allowing RNP (genome) from M1 to be released to the cytoplasm and later be transported to the nucleus

Question 13

RNP (genome) is moved to the nucleus via nuclear pores that is coated by NP, why?

Answer 13

to prevent degradation (protected)

Question 14

Each of the 8 segments of (-) RNA is copied into ….. by …. independently

Answer 14

(+) complementary strand RNA by viral RNA Polymerase (RDRP)

Question 15

What is the (+) complementary strand RNA used for

Answer 15

as a template for translation of proteins

Question 16

The main challenge for RDRP is that it needs a primer, what does the virus do to tackle it?

Answer 16

It does “cap stealing” where RDRP cuts off the 5’ cap from host mRNA so they have the 3’OH group
kills the cell’s mRNA

Question 17

So the virus now has a 5’ cap, but they still need a 3’ poly-a-tail, which they don’t have. This causes the ribosomes unable to read and translate. What is the solution

Answer 17

Stuttering to produce a stable Poly(A)tail
RDRP produces polyadelynation signals on the U stretch and stutter

Question 18

what marks the end of transcription

Answer 18

stuttering

Question 19

what is a panhandle structure

Answer 19

when RNA Pol. Complex (RDRP) anchors the 5’ end of the (-) strand, and the last 15-22 nucleotides aren’t copied

Question 20

What are the two advantages of cap stealing

Answer 20

makes the viral mRNA looking like host mRNA because it has a 5’ cap
stealing kills the cell mRNA, so eliminates competition
==== attracts ribosomes

Question 21

Where does translation take place (influenza virus)

Answer 21

cytoplasm

Question 22

Before translation, mRNA is spliced to make it monocistronic, then that mRNA goes either 2 ways, which are;

Answer 22

(a) translated into envelope proteins
- H, N, M2
- via ribosomes on ER

(b) translated into other viral proteins
- NP, PA, PB1, PB2, M1
- via free ribosomes

Question 23

Which proteins return to the nucleus, and why?

Answer 23

NP, PA, PB1, PB2
to start genome replication, to make more copies of the viral genome

Question 24

The replication of viral genome (in the last step) doesn’t involve,…..why?

Answer 24

primer or cap stealing because its making a genome, and not translating proteins

Question 25

To start replication, RNA polymerase complex binds to...

Answer 25

(-) RNA genome

Question 26

after RPC binding to (-) RNA genome, what is produced

Answer 26

(+) strand produced

Question 27

This (+) strand RNA is full length, what does that mean?

Answer 27

It means that the RNA pol ignores the stop and start signals (transcription signals)

Question 28

The (+) RNA strand is coated with NP, why?

Answer 28

to protect and stabilize it

Question 29

After the (+) RNA strand is produced, what helps produce the (-) viral RNA genome

Answer 29

newly synthesized RNA Polymerase proteins (PA, PB1, PB2, NP)

Question 30

What is an antigenome in the terms of influenza virus replication cycle

Answer 30

(+) RNA

Question 31

So, the viral replication of influenza results in...

Answer 31

10 different types of proteins coming from 8 segments of RNA and a new (-) strand of RNA genome

Question 32

What happens in the assembly of the virus particle

Answer 32

- Envelop proteins made on ER moves up to the plasma membrane - RNA genome, RNA Pol Complex, NP, M are exported out of the nucleus following to the plasma membrane

Question 33

then it's leaves the cell through...

Answer 33

budding

Question 34

what protein promotes membrane fussion to detach the virus from the cell (influenza)

Answer 34

M2

Question 35

what protein "frees" the virus particle from the cell by removing sialic acid?

Answer 35

N (Neurominidase)

Question 36

The pH of the endosome causes a conformational change of the H protein so that a fusion peptide is revealed, is that true or false

Answer 36

true

Question 37

The H envelope protein of influenza virus is modified by a lysosomal enzyme after entry into the host cell, true or false

Answer 37

false, The H (hemagglutinin) protein of influenza virus is cleaved by tryptase Clara before or during entry, and undergoes a conformational change in the acidic endosome, exposing the fusion peptide.

Question 38

The influenza virus must cleave structures on cell membrane to free itself. T or F

Answer 38

T, N cleave SA

Question 39

Since influenza virus replicates in the nucleus of the infected cell, it uses the cellular polyadenlyation enzymes to add the poly(A) tail on the viral mRNAs. T or F

Answer 39

F, because the signals are produced by RDRP, not the cell