Virology1 Flashcards
What s the Baltimore classification
1 - dsDNA - herpes 2 - ssDNA - parvo 3- dsRNA - reo 4 - ssRNA +sense - polio 5 - ssRNA -sense - influenza, measles 6 - ssRNA +sense DNA intermediate - HIV 7 - dsDNA, RNA intermediate - HBV
Which viruses use viral DNA polymerase?
Herpesvirus
Which virus uses host DNA polymerase?
Parvo
which virus uses viral RNA dependent RNA polymerase?
Rota, polio, influenza
which virus uses viral RNA dependent DNA polymerase?
HIV, HBV
What type of virus is influenza?
Class 5, Orthomyxovirus, segmented genome
Draw a diagram of an influenza virus
picture lol
what are the segments of influenza in order - largest to smallest?
- PB2
- PB1, PB1-F2
- PA, PA-X
- HA
- NP
- NA
- M1, M2, M3
- NS1, NS2
What is the active form of HA
trimer
How is sialic acid linked to galactose in humans?
a-2, 6 linkage
How is sialic acid linked to galactose in ducks?
a-2,3 linkage
What are the 3 stages in influenza virus mRNA synthesis?
- Cap snatching
2 Cleavage - Elongation
What is the function of NP
- Associates with - strand genome RNA
What is the function of NP
- Associates with - strand genome RNA
- Binds to cRNA and allows antitermination at polyA site so it can make a vRNP once it has been stabilised by NP
What is the function of PB2
- Binds cap of host mRNA
What is the function of PA
- Cleaves capped mRNA to produce cap and 10-12 nucleotides
where does polyadenylation occur in mRNA synthesis of influenza?
17-22 bases from the 5’ end of the genome at a poly U tract
where does polyadenylation occur in mRNA synthesis of influenza?
17-22 bases from the 5’ end of the genome at a poly U tract
Describe the timing of influenza synthesis
- mRNA –> cytoplasm
- viral proteins made. Pol and NP enter nucleus
- cRNA stabilised as cRNP
- many copies of vRNA can be made from each cRNP
- vRNA stabilised as vRNP and exported into cytoplasm for assembly.
How is segment 2 translated in influenza?
Different start codons in different reading frames via leaky scanning
How is segment 3 translated in influenza?
Proteins have common N terminus, diff C terminus via ribosomal frameshifting
How is segment 7 translated in influenza?
Splicing to give 3 different mRNAs coding for different proteins
How is segment 8 translated in influenza?
Splicing to give 2different mRNAs coding for different proteins
What is the role of PB1-F2?
virulence factor, increases inflammation in the host
What is the role of PA-X?
Host cell shut off gene expression, non-specific mRNA cleavage protein, dampens host antiviral response - anti-inflammation
What is the role of NS1?
- Promote translation of viral mRNA
- IFN antagonist
- Inhibit nuclear export of cellular mRNA
How does RNP export occur?
Via Crm1
M1 binds vRNP
NS2 binds M1 and interacts with Crm1 - part of the nuclear pore complex
vRNPs can be exported through the nuclear pore into the cytoplasm
What is the role of NA?
Removes sialic acid from HA and prevents aggregation of new virions with each other and with the surface of the infected cell. allows viruses to leave the cell.
