Deck 11: Picornaviruses

Question 1

The VPg protein from picornaviruses has which of the following function?

A)It acts as a primer for RNA synthesis.
B)It is the RNA-dependent RNA polymerase.
C)It is the protease the cleaves the viral polyprotein.
D)It induces the formation of cellular membranes.
E)It packages the viral genome into capsids.

Answer 1

A

Question 2

Some picornaviruses have depressions,called "canyons",on the surface of the virions.Which of the following describes the role that these depressions play?

A)They release the viral genome into the host cell.
B)They bind to the host cell receptor.
C)They maintain the stability of the capsid.
D)They bind to antibodies.
E)They adhere to the envelope.

Answer 2

B

Question 3

In the picornavirus genome,there are several A nucleotides found at the 3' end of both the positive and negative sense strands.How are these A nucleotides used in replication of the RNA genome?

A)They function as the poly A tail for translation of both strands.
B)They provide energy for the RNA-dependent RNA polymerase.
C)They allow the genome strands to be easily separated.
D)They basepair with the U nucleotide bound to the VPg protein.
E)All of the above are correct.

Answer 3

D

Question 4

Picornaviruses cause cytopathic effects in infected host cells by doing all of the following EXCEPT:

A)Inhibiting cap-dependent translation of mRNAs.
B)Degrading cellular DNA.
C)Inhibiting intracellular transport from the ER to the Golgi.
D)Cleaving histone H3 protein.
E)Inhibiting host cell mRNA synthesis.

Question 5

Which of the following diseases is NOT caused by a member of the picornavirus family?

A)Common cold
B)Polio
C)Hepatitis A
D)Influenza
E)Foot-and-mouth disease

Question 6

Once the viral genome has entered the host cell,poliovirus does not require any of the virion proteins to carry out its infectious cycle.

Question 7

The killed Salk and live Sabin vaccines have been used successfully to nearly eliminate which of the following viruses from the human population?

A)Polio
B)Smallpox
C)Measles
D)Hepatitis A
E)Foot-and-mouth disease

Question 8

Why is it unlikely that there will ever be an effective vaccine against the rhinovirus,the major cause of the common cold?

A)The immune system is not very effective at attacking rhinoviruses.
B)There are over 100 different serotypes of rhinovirus.
C)The immune system does not protect the nose.
D)The common cold is too fast for the immune system to fight off.
E)Antibodies can not bind to the rhinovirus virion very well.

Question 9

Why do many positive-strand RNA viruses form their genome replication complexes on the surface of cytoplasmic membranes?

A)Genome replication requires cellular membrane bound proteins.
B)This allows the RNA to be replicated close to the site of virion assembly.
C)The membrane acts as a nucleation sites to bring all of the proteins together.
D)The membrane protects the viral genome during replication.
E)Fatty acids are required co-factors of the viral polymerase.

Question 10

Which of the following describes the last step in the maturation of the picornavirus capsid?

A)Assembly of the 5S protomer
B)Packaging of the viral genome.
C)Cleavage of P1 polyprotein into VP0,VP1 and VP3.
D)Cleavage of VP0 into VP2 and VP4.
E)Assembly of the 14S pentamer.

Question 11

Many of the picornaviruses use host cell receptors that have which of the following characteristics?

A)They are phospholipids.
B)They are carbohydrates.
C)They belong to the immunoglobulin superfamily.
D)They are integrins.
E)They are ion channels.

Question 12

Since translation of mRNAs in eukaryotic cells produces only a single polypeptide,how do picornaviruses produce multiple proteins from their RNA genome?

A)They produce multiple subgenomic mRNAs.
B)Their genome consists of a multicistronic mRNA.
C)They use multiple IRES regions to translate multiple open reading frames.
D)They have internal translation start sites in their genome.
E)They cleave a single polypeptide into individual proteins.

Question 13

How does cleavage of the host cell protein eIF-4G give the virus a competitive advantage?

A)It releases translation factors that the virus needs.
B)It inhibits a cellular nuclease that would degrade the viral genome.
C)It prevents translation of host cell mRNAs but not viral genomes.
D)It inhibits host cell defense mechanisms.
E)It releases nucleotides to be used in viral genome replication.

Question 14

The ability of picornaviruses to cause pathogenesis in specific tissues can be localized to which of the following regions of the viral genomic RNA?

A)The RNA-dependent RNA polymerase coding region.
B)The 3' noncoding region.
C)The non-structural protein coding region.
D)The capsid protein coding region.
E)The 5' noncoding sequence.

Question 15

Entry of the poliovirus genome into the host cell involves all of the following EXCEPT…

A)Binding to a host cell receptor
B)Extrusion of the hydrophobic N-terminus of VP1
C)Conformational change of the virion
D)Loss of the internal VP4 protein
E)Acidification of the endosome

Question 16

Which of the following describes the source of the protease that cleaves the picornavirus polyprotein into individual functional proteins?

A)It is a cellular protease.
B)It is brought into the host cell with the virion.
C)It is part of the polyprotein.
D)It is one of the capsid proteins.
E)It is a complex of a viral and a cellular protein.

Question 17

The poliovirus protease cleaves the cellular eIF-4G protein.Why doesn't this affect the virus?

A)The virus doesn't use this protein as its host cell receptor.
B)The virus encodes the poly A tail as part of the genome.
C)The virus encodes its own version of this cellular protein.
D)The virus does not use cap-dependent translation.
E)The virus encodes its own RNA-dependent RNA polymerase.

Question 18

Translation initiation of the genomes of picornaviruses require all of the following EXCEPT:

A)IRES at the 5' end of the genome
B)VPg protein attached to 5' end of genome
C)Pyrimidine-rich sequence upstream of an AUG
D)Small subunit of ribosome
E)Host cell translation initiation factors

Question 19

The poly A tail found at the end of the picornavirus genome is created using the same mechanism as the poly A tails on host cell mRNAs.

Question 20

The 5' end of the poliovirus genomic RNA contains all of the following EXCEPT…

A)A 5' cap
B)An unusually long noncoding region
C)A pyrimidine-rich tract
D)A high degree of RNA secondary structure
E)Multiple AUG start codons

Question 21

Hepatitis A produces less cytopathic effects in infected cells than other picornaviruses.

Question 22

Explain how the rhinovirus capsid can evolve to evade the immune system yet can still bind and recognize the same host cell receptor.

Question 23

The RNA-dependent RNA polymerase from picornaviruses does not require a primer.

Question 24

The 3C proteinase from picornaviruses can cleave itself out of the intact polyprotein.

Question 25

Poliovirus virions enter cells through a pH independent mechanism at the cell surface,which is an unusual pathway for a naked virion.Describe the entry mechanism and explain why this is this important for a virus that uses the oral-fecal transmission route?

Question 26

Instead of a 5' cap on the viral genomic RNA,genomes of the picornaviruses have a covalently bound protein.In addition,the viral 3C protease cleaves a major component of the cap binding complex.This situation should inhibit translation initiation of the picornaviral RNA into protein.Explain how the virus "solves" this problem.