Final Flashcards
(80 cards)
What is the genome of influenza?
8 pieces of negative ssRNA
Describe the process of transcription of the influenza genome
Genome comes with viral replicase and is a template to make + mRNA which is then translated into 10 proteins
What segments of the influenza genome are alternatively spliced and what do those proteins do
segement 7 can make the M1 matrix or M2 protein while segment 8 can make the NS 1 or 2 protein
What is the life cycle of the influenza virus
cell takes up virus by fusing membranes together, RNA and RNAP are released into the cytoplasm, they enter the nucleus, transcription is primed via decapitated host cap, then paths diverge
After divergence of paths, what happen in the nucleus for influenza
+mRNA is made in the nucleus, mRNA is brough to the cytoplams for translation where is encodes membrane glycoproteins that go to the ER and makes envelope proteins that embed themselves on the surface of the cell to wait for the virus
After divergence of paths, what happens in the cytoplasm for influenza
mRNA goes to cytoplasm then nucleus and waits for high concentration where it will switch to replication.
-mRNA is transcribed into +mRNA without 5’ caps allowing full lenght copies of mRNA to be made. This becomes template for multiple copies of -mRNA that are packed by NP protein and transported to envelope proteins.
Once viruses are packaged, how do they leave the cell for influenza
Virus buds off cell and neuraminidase cleaves sialic acids that tangle virus only viruses are not infectious yet. Hemagglutinin protein needs to be cleaved into HA1 and 2 via host protease
How does influenza make it into a cell
Hemagglutinin binds to sialic acid of cell, cell then takes in virus via endocytosis. Once in endosome of cell, acidification happens to try and destroy virus but this helps virus by altering structure resulting in hemagglutinin conformation change such that membranes fuse together.
How does influenza acquire 5’ caps
5’ caps are taken from host mRNA allowing primer for virus to make +ssRNA and stops protein synthesis for host
Why is there no spread of avian influenza from person to person
The avain hemagglutinin is likely not able to be process by human proteases into HA1 and 2 so it does not become infectious or the HA might find more receptors in the lower respiratory tract rather than upper tract so not spread as mcuh
What is the use of influenza A having 11 pieces of RNA
In the event that disadvantagous mutations occur there will be some outcomes in which the correct 8 segments come together
What is antigenic shift
Rapid alteration in genotype and phenotyp of virus due to different RNA segments
What is Antigentic drift
random genetic mutation of an infectious agent resulting in changes in proteins
How does antigenic drift happen in influenza
viral replicase is not checked resulting in a high mutation rate and a lot of viral deaths
What is the genome of retroviruses
two identical +ssRNA strands
What enzymes does retrovirus bring into the cell
Reverse transcriptase to make a DNA copy of RNA, integrase to recombine DNA and protease which processes proteins when they leave cell
What are the three genes of a typical retrovirus
GAG group antigens that are capsid proteins, POL polymerase and integrase, and ENV envelope glycoproteins
What are the receptors the HIV binds to and how
CD4 and either CCR5 that is used for initial infections and CXCR4 used later in infection to attack immune system. Bound to via gp 160 that cleaves into gp 120 and 41 which causes membrane fusion
What is the processes of CD4 infection
Once genome is in cell, GAG genes encode capsid protein that goes to nucleus along with other genes for replication. Reverse transcriptase makes a dsDNA copy of genome resulting in LTRs on genome instead of repeats. Integrase uses LTRs to place genome into host genome so that mRNA is made exactly like the one that entered cell
What are the two forms of retroviral mRNAs
Spliced which has ENV genes and unspliced which has GAG and POL genes
How does the unspliced from of retroviral mRNA get translated
Ribosomes bind to mRNA and translate to stop codon making giant GAG protein that goes through autoproteolysis. 10% of the time stop codon is ignored resulting in GAG and POL protein that is cleaved resulting in reverse transcriptase and integrase. Stop codon is a programmed frameshift due to pseudoknot that confuses ribsome before is continues on with an extra codon
What are the regulatory proteins in HIV 1, what do they do, and when are they expressed
nef, negative factor that downregulates CD4 expresssion to prevent superinfection and is expressed early, rev, allows unspliced forms of mRNA into the cytoplasm and is expressed early, and vpu, viral protein U allows viruses to not get stuck to cell once released from cell
What is the genome of coronavirus and what does it enter the cell with
+ ssRNA and is a really really big genome and enters cell with exonuclease that proofreads RNAP products
Why are bats great reservoirs of diseases
They are the only mammals to fly and have tremendous metabolic demand which might have caused damage to cells releasing a lot of DNA. This likely resulted in bats’ mutation of STING causing a reduced inflammatory response to viurses thus they built tolerance to viral infections