Picorna Viruses and Myxoviruses

Question 1

What kind of genome do picorna viruses have?

Answer 1

+ SS RNA

Question 2

What type of protein is encoded by picorna viruses?

Answer 2

A single polyprotein that is later cleaved.

Question 3

What does the picorna 5’ VpG protein do?

Answer 3

Serves as a primer for translation of the viral genomic (+) mRNA

Question 4

Do picorna genomes have 5’ modifications or poly A tails?

Answer 4

Yeah, the 5’ cap is the VpG protein

Question 5

Do picorna viruses require host cell nuclear function to replicate?

Answer 5

Nope

Question 6

Where does initiation of translation occur on the picorna RNA?

Answer 6

At an internal site.

Question 7

Do picorna viruses encode a protease that cleaves host mRNA 5’ caps?

Answer 7

Yeah

Question 8

What does the picorna virus replicase do?

Answer 8

It associates with viral genome RNA and a VpU protein that has been added to the 3’ end of the RNA to copy the viral genome, including the poly-A tail

Question 9

What happens to picorna virus capsid proteins after RNA is stuffed into them during synthesis of new virions?

Answer 9

Proteolytic cleavage allows the proteins to pack tightly.

Question 10

What type of virus is influenza?

Answer 10

Myxovirus

Question 11

How are myxoviruses classified?

Answer 11

By the antigenicity of their surface proteins Hemagglutinin (HA) and Neuraminidase (NA).

Question 12

What type of genome do myxoviruses have?

Answer 12

Segmented (-) RNA.

Question 13

What can viruses with segmented genomes do rapidly?

Answer 13

Recombine to make novel stereotypes

Question 14

Do viral (-) strand RNA genomes have 5’ proteins or poly A tails?

Answer 14

No - they need to be replicated into + strand mRNA first.

Question 15

What does Hemagglutinin of a myxovirus do?

Answer 15

Binds host cell receptor.

Question 16

What does Neuraminidase of a myxovirus do? Why does it do this?

Answer 16

Degrades the host cell receptors so that 1) free-floating side chains that bind to the virus can be cleaved off and 2) so that not more than one virus infects a cell.

Question 17

How do myxoviruses get into cells?

Answer 17

RME –> vesicle acidification –> capsid fusion with membrane –> release of viral genome into cytoplasm.

Question 18

Describe the agglutination assay.

Answer 18

Mix virus and RBCs in test tube. Viruses will bind RBCs to form aggregations that sink to the bottom of the tube. Can also test antibodies this way - if the Ab works, no aggregations form.

Question 19

Where do myxoviruses get primers for genome replication?

Answer 19

They steal 5’ caps from host mRNA to use as primers for viral RNA replication.

Question 20

What does myxovirus NP protein do?

Answer 20

It is normally translated from the genome. Once it builds up in the cytoplasm it goes into the nucleus to sequester (+) RNA that is being synthesized so that it can then be used to make viral (-) RNA for packaging into new virions.