15. Adenovirus 2 Flashcards
what is pTP and its function?
pre-terminal protein which primes replication
describe the first phase of adenovirus replication (3 steps)
- pTP binds C on the end of DNA opposite of TP
- DNA pol starts replicating and displaces a ssDNA
- produces 1 dsDNA and 1 displaced ssDNA associated with DNA binding protein
describe the second phase of adenovirus replication (4 steps)
- the displaced ssDNA folds on itself at the inverted terminal repeats to make pan-handle structure
- a new pTP joins at a C opposite the TP
- DNA pol replicates and displaces the DNA binding protein
- produces another dsDNA
what happens once the genome is replicated? why?
late stage proteins can be made bc the late proteins are made from this new DNA
how many late proteins are there?
14
how many promoters are there for the late proteins?
1 major late promoter
how is it possible that there are 14 late proteins but 1 promoter? why does this let the virus be more efficient
ALTERNATIVE SPLICING!
can pack a lot of info into genome
describe the 5 steps of alternative splicing
- DNA transcribed to make 1 long RNA transcript
- transcript is poly-adenylated by cellular machinery at 5 different sites
- this gives different splice sites where transcript is spliced by cellular machinery
- tripartite leader is assembled
- many proteins can be made
does the machinery for poly-adenylation and splicing come from the virus or the cell?
cell!
where is the packaging sequence in the genome?
at the beginning
which mRNA have the tripartite leader?
tripartite leader is spliced onto every late mRNA
What do IVa2 and L2 52/55k do?
join to form ATPase driven motor
what is the role of L4 33K/100K?
viral chaperones/scaffolds for capsid assembly
can adenovirus capsid self-assemble?
no, requires chaperones and scaffold proteins
what is the role of E4 Orf4 and E3 11.6K?
to induce apoptosis once the viral life cycle has completed to leave the cell
how does E1A induce apoptosis?
- E1A binds Rb to allow E2F promoter to be active
- p14 ARF is produced
- p14 ARF binds MDM2 to stabilize p53
- stabilized p53 = apoptosis
what is MDM2 function? how does p14 ARF affect it?
ubiquitinates p53 so it can be degraded
but p14 ARF binds MDM2 to prevent p53 from being degraded
which oncogene inhibits p53?
E1B-55K
how does E1B-55K inhibit p53? what does this result in?
sequesters p53 to inhibit it –> no apoptosis, cell can survive
E1A and E1B vs E6 and E7
E1A = E7
E1B = E6
what are oncolytic virus?
genetically engineered viruses that can induce immune system and kill tumour cells
what is the other type of E1B?
E1B-19k
what is the role of E1B-19K
inhibits Bax in mitochondria to inhibit apoptosis
what does Bax do? how is it upregulated?
Bax forms pores at mitochondria to eventually induce apoptosis
upregulated by p53
do E1B-55K and E1B-19K work together or is only 1 used?
both work together to maximize inhibition of apoptosis
what type of RNA is VA RNA?
non-coding RNA
what are the 3 functions of VA RNA?
- inhibit PKR activation
- block nuclear export of pre-mRNAs
- inhibit dicer
what is PKR? how does VA RNA affect it?
detects virus infection by binding the dsRNA
- Phosphorylates itself then phosphorylates eIF2a to inhibit translation
VA RNA blocks this –> translation can continue
why does PKR recognize a viral infection?
dsRNA is only present in a cell when a virus has infected it
what is the role of E3?
immunosuppression to make infected cell bypass immune system
can we see E3 function in cell culture?
no, it only works in an in vivo system where the immune system is present
what are 3 functions of E3?
- internalize TNF/fas receptors so cell can’t recognize virus
- inhibit MHC complex so cell can’t present peptides
- makes Adenovirus Death Protein so virus can easily be released from cell
