lecture 5/6 banfield Flashcards
explain the characteristics of picornaviruses!
i.e. genetic info, location of replication, size, etc
- small (opposite to pox which are large
- (+) strand RNA viruses
- they have naked (non-enveloped) icosahedral capsids
- they replicate in the cytoplasm
what are a couple known picornaviruses?
polio, common cold, meningitis, hepatitis,
t or f, polio was the first virus to be crystallized with its atomic structure.
true
explain rhino virus
- 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
t or f, humans are the only host of picorno rhino virus that does not exhibit all of its symptoms
false, humans are the only host that DO EXHIBIT all symptoms
explain the polio capsid structure
it is an icosahedral capsid build by 4 proteins VP1,2,3,4.
explain the polio virus genome
it is a +strand RNA virus that contains a protein called VPG on its 5’ end. This acts as the primer for transcription.
explain polio virus general transcription
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. .
explain general picornavirus replication
- virus binds outside of cell and injects +RNA in
- since its +strand it can be translated right away
- the protein its translated to gets cut by proteases for different functional proteins.
- the +RNA is also transcribed to form a -RNA for replication template.
what is the name of the 5’ location that allows direct translation of the +RNA of picornaviruses
Internal ribosomal entry site (IRES)
how do polio viruses shut down host cell protein synthesis?
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!
Influenza virus A, B, and C are all what kind of virus?
Orthomyxoviruses
explain orthomyxoviruses (genome, capsid, etc)
segmented (-) RNA genome.
it is an enveloped virus. replication occurs in the nucleus!! (unlike most RNA viruses)
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?
true
explain the influenza A subtypes
influenza A (orthomyxovirus) can be divided base on two proteins.
1. hemagglutinin (H).
2. neuraminidase (N)
there are 18H and 11N subtypes
what are the symptoms of the influenza viruses?
- 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)
what does it mean when we say the influenza viruses (orthomyxoviruses) have segmented genomes?
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
how do orthomyxoviruses and picornaviruses differ in their genomes?
picorna –> +RNA that makes a polyprotein with proteases. Poly-protein is then cleaved
Ortho –>
-RNA that is segmented (different codes for different proteins)
true or false, the influenza virus ( -) strand RNA segments each have a RNA polymerase bound to it.
true, this is there so that the (-) RNA can be transcribed into +RNA for translation.
What is the NEP protein?
nuclear import protein which allows the orthomyxoviruses segmented -strand into the nucleus..
t or f, the influenza virus can stop host protein synthesis by stealing mRNA 5’ caps from host mRNA. q
true
t or f, influenza virus is pH independent fusion to enter the cell
false, it requires an acidic environment both in its endosome and for HA glycoprotein to bind
