Acheson Chap 19 Reoviruses

Which of the following factors affect the abundance of the viral proteins produced during infection with a reovirus?

a) Length of the mRNA

b) Sequences surrounding the start codon

c) Length of the 5’ noncoding sequences

d) Secondary structure in the 5’ noncoding sequences

e) All of the above are correct

e) All of the above are correct

Which of the following describes the type of nucleic acids found in reovirus genomes?

a) Single-stranded positive-sense RNA

b) Single-stranded negative-sense RNA

c) Double-stranded RNA

d) Single-stranded DNA

e) Double-stranded DNA

c) Double-stranded RNA

How has the creation of reassortant viruses helped in the study of reoviruses?

a) It allows for the infection of new hosts via antigenic shift

b) It allows for the association of a specific viral protein with its function

c) It allows scientists to measure the size of the various genome segments

d) It allows for easier identification of specific virion protein

e) It allows for the creation of new gene therapy vectors

b) It allows for the association of a specific viral protein with its function

Which of the following describes an interesting feature of the reovirus virion?

a) It has two envelopes, one inner and one outer

b) The envelope has icosahedral symmetry, same as the underlying capsid

c) Each genome segment is wrapped into a helical nucleocapsid

d) The capsid consists of two concentric shells, both with icosahedral symmetry

e) The mature virion has open passages at each of the twelve vertices

d) The capsid consists of two concentric shells, both with icosahedral symmetry

Which of the following is NOT a host cell protein that can be used as a receptor by a reovirus?

a) Cathepsin

b) Sialic Acid

c) JAM-A

d) Integrin

e) None of the above

a) Cathepsin

Which of the following is the first step in the expression of reovirus proteins during the infection?

a) Translation of the incoming RNA segment into protein

b) Copying of the positive strand of each genome into a negative strand

c) Copying of the negative strand of each segment into an mRNA

d) Capping of the positive strand of each genome segment

e) Translation of the positive strand of each genome segment

c) Copying of the negative strand of each segment into an mRNA

What is the source of the nucleotide triphosphates used to make reovirus mRNAs?

a) They are produced by enzymes inside the core virion

b) They diffuse into the core virion from the cytoplasm

c) RNA synthesis occurs in the cytoplasm, where the nucleotides are located

d) The viral RNA polymerase transports them into the core virion

e) They are brought inside the virion from the previous host cell

b) They diffuse into the core virion from the cytoplasm

All of the following are enzymatic activities found within the virion core of reoviruses EXCEPT:

a) RNA-dependent RNA polymerase activity

b) RNA helicase activity

c) Phosphatase to remove 5’ end of mRNAs

d) Methyltransferase

e) Peptidyl transferase

e) Peptidyl transferase

Which of the following reovirus proteins is implicated in selective inhibition of PKR activation in infected cells?

a) σ1

b) σ3

c) μ1

d) μ2

e) λ1

b) σ3

Which of the following mechanisms explain how reovirus mRNAs acquire their poly(A) tail?

a) They do not have poly(A) tails but use other sequences to functionally substitute

b) Cellular enzymes add the poly(A) tail

c) Viral enzymes in the virion core add the poly(A) tail

d) They encode a poly(A) tail in each genome segment

e) The RNA polymerase stutters at a poly(U) region at the end of each genome segment

a) They do not have poly(A) tails but use other sequences to functionally substitute

Which of the following describes the mechanism used by reoviruses to ensure that one of each of the 10 genome segments is packaged into the virion?

a) Reoviruses do not have a specific mechanism to ensure packaging of each genome segment into the virion

b) Each double-stranded RNA segment has a unique packaging sequence

c) One of each double-stranded RNA segments binds to the capsid proteins

d) One of each mRNA is assembled into a virus factory

e) None of the above are correct

d) One of each mRNA is assembled into a virus factory

Which of the following is used as the template for the production of more reovirus genome segments in the virus factories?

a) Double-stranded RNA

b) Single-stranded negative sense RNA

c) mRNAs

d) Single-stranded positive sense RNA

e) Both c and d are correct

e) Both c and d are correct

Which of the following accounts for the majority of the viral mRNA synthesized in a reovirus infected cell?

a) mRNA made from single-stranded negative RNA segments

b) mRNA made from incoming double-stranded RNA segments

c) mRNA made from newly synthesized double-stranded RNA segments

d) mRNA made from RNA segments found in the cell nucleus

e) mRNA made from virions found in the lysosome

c) mRNA made from newly synthesized double-stranded RNA segments

Infection of a cell with a reovirus can activate which of the following cellular proteins or processes?

a) NF-κB

b) IRF-3

c) Apoptosis

d) Caspases

e) All of the above are correct

e) All of the above are correct

Reoviruses cause cell-cycle arrest in infected cells. At what point in the cell cycle do these viruses halt the cell cycle?

a) Between mitosis and G1

b) Between G1 and S

c) Between S and G2

d) Between G2 and mitosis

e) All of the above

d) Between G2 and mitosis

Reoviruses keep their genome sequestered inside the inner capsid throughout the entire infectious cycle. Which of the following is the best explanation for why they do not release the genome segments out into the cytoplasm?

a) The double-stranded RNA segments activate the interferon response

b) There are cellular enzymes that specifically degrade double-stranded RNA

c) The RNA segments cannot be translated by the cellular ribosomes

d) Double-stranded RNA is sequestered into special compartments within the cytoplasm

e) There are cellular proteins that will bind double-stranded RNA and inhibit it

a) The double-stranded RNA segments activate the interferon response

Reoviruses have been used to study viral pathogenesis in mice. Using virus reassortants, which of the following has been shown to be a major determinant for infection of the nervous system in a mouse?

a) Activation of the host cell immune system

b) Binding of the virus to different host cell receptors

c) Activation of the interferon system in host cells

d) The rate of viral mRNA synthesis in host cells

e) The rate of genome synthesis in host cells

b) Binding of the virus to different host cell receptors

Reoviruses can cause myocarditis in infected mice but it is through a different mechanism than used by most other viruses that cause this disease. Which of the following describes the reason reoviruses destroy heart muscle?

a) Reoviruses induce cytopathic effects in heart muscle

b) Reoviruses induce apoptosis in the heart muscle

c) Reoviruses induce interferon in the heart muscle

d) Reoviruses induce the immune system to destroy the heart muscle

e) Reoviruses induce the RNAi pathway in heart muscle

a) Reoviruses induce cytopathic effects in heart muscle

True or False? Some reoviruses are transmitted by insects and are therefore examples of arboviruses.

True

True or False? The RNA-dependent RNA polymerase of reoviruses is released into the cytoplasm along with the double-strand RNA segments.

False

True or False? There is evidence that the noncoding sequences on reovirus genome segments are highly conserved.

True

True or False? Most reovirus virions must be partially degraded by proteases in the lysosome before infection.

True

True or False? Infectious subvirion particles are intermediates in the assembly of reovirus virions.

False

True or False? Reoviruses replicate more poorly in transformed cells than in normal cells.

False

True or False? Reovirus capsid proteins assemble around positive-strand RNA segments before completion of genome replication.

True