lecture 5/6 banfield

Question 1

explain the characteristics of picornaviruses!

i.e. genetic info, location of replication, size, etc

Answer 1

• small (opposite to pox which are large
• (+) strand RNA viruses
• they have naked (non-enveloped) icosahedral capsids
• they replicate in the cytoplasm

Question 2

what are a couple known picornaviruses?

Answer 2

polio, common cold, meningitis, hepatitis,

Question 3

t or f, polio was the first virus to be crystallized with its atomic structure.

Answer 3

true

Question 4

explain rhino virus

Answer 4

• a type of picornavirus
• causes the common cold
• transmits via aerosols and contact
• has thermo and acid liable capsid (unstable in heat and acid)
• 150 strains making vaccine impossible

Question 5

t or f, humans are the only host of picorno rhino virus that does not exhibit all of its symptoms

Answer 5

false, humans are the only host that DO EXHIBIT all symptoms

Question 6

explain the polio capsid structure

Answer 6

it is an icosahedral capsid build by 4 proteins VP1,2,3,4.

Question 7

explain the polio virus genome

Answer 7

it is a +strand RNA virus that contains a protein called VPG on its 5’ end. This acts as the primer for transcription.

Question 8

explain polio virus general transcription

Answer 8

it uses a poly-protein strategy. it has protease genes within the segment to be transcribed. The translated proteases chop up the poly protein into smaller proteins. .

Question 9

explain general picornavirus replication

Answer 9

1. virus binds outside of cell and injects +RNA in
2. since its +strand it can be translated right away
3. the protein its translated to gets cut by proteases for different functional proteins.
4. the +RNA is also transcribed to form a -RNA for replication template.

Question 10

what is the name of the 5’ location that allows direct translation of the +RNA of picornaviruses

Answer 10

Internal ribosomal entry site (IRES)

Question 11

how do polio viruses shut down host cell protein synthesis?

Answer 11

polio produces a protease that cleaves a host transcriptional factor half. This TF is needed for mRNA binding to the ribosome which now cant happen. The polio virus IRES still allows it to use the ribosome. The virus has figured out how produce its own proteins while also inhibit the production of host proteins!

Question 12

Influenza virus A, B, and C are all what kind of virus?

Answer 12

Orthomyxoviruses

Question 13

explain orthomyxoviruses (genome, capsid, etc)

Answer 13

segmented (-) RNA genome.

it is an enveloped virus. replication occurs in the nucleus!! (unlike most RNA viruses)

Question 14

A and B influenza are seasonal viruses that are considered epidemics, C is a mild respiratory illness and is not considered an epidemic.. t or f?

Answer 14

true

Question 15

explain the influenza A subtypes

Answer 15

influenza A (orthomyxovirus) can be divided base on two proteins.
1. hemagglutinin (H).
2. neuraminidase (N)
there are 18H and 11N subtypes

Question 16

what are the symptoms of the influenza viruses?

Answer 16

• rapid onset of infection in lower and upper respiratory tract
• causes fever and malaise
• old ppl and young ppl at risk
• transmitted by aerosols and contact (d and ind)

Question 17

what does it mean when we say the influenza viruses (orthomyxoviruses) have segmented genomes?

Answer 17

each “segment” of the genome encodes for a different protein. There are multiple genome pieces, each transcripbed and translated into different proteins. (all segments start as -RNA strand

Question 18

how do orthomyxoviruses and picornaviruses differ in their genomes?

Answer 18

picorna –> +RNA that makes a polyprotein with proteases. Poly-protein is then cleaved

Ortho –>
-RNA that is segmented (different codes for different proteins)

Question 19

true or false, the influenza virus ( -) strand RNA segments each have a RNA polymerase bound to it.

Answer 19

true, this is there so that the (-) RNA can be transcribed into +RNA for translation.

Question 20

What is the NEP protein?

Answer 20

nuclear import protein which allows the orthomyxoviruses segmented -strand into the nucleus..

Question 21

t or f, the influenza virus can stop host protein synthesis by stealing mRNA 5’ caps from host mRNA. q

Answer 21

true

Question 22

t or f, influenza virus is pH independent fusion to enter the cell

Answer 22

false, it requires an acidic environment both in its endosome and for HA glycoprotein to bind