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MGY378 > Adenovirus (Dr. Frappier) > Flashcards

Adenovirus (Dr. Frappier) Flashcards

1
Q

Discoveries from adenovirus

A

i) 1st human virus shown to induce cancer
ii) alternative RNA splicing

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2
Q

Types of adenovirus

A

one for mammals, one for birds

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3
Q

components of capsid

A

hexon, penton

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4
Q

what is found in penton

A

a base + projecting fibre

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5
Q

feature of genetic material

A

linear ds DNA
+ terminal protein attached to 5’ ends
+ inverted terminal repeats

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6
Q

What is VII in virion core similar to?

A

histone

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7
Q

What is the function of VII?

A

protect genome from being recognized by host DNA damage response

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8
Q

What is found in virion core?

A

linear dsDNA
4 proteins (V, VII, X, terminal protein)

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9
Q

where does terminal protein attach to?

A

5’ end of each viral DNA strand

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10
Q

What cell receptor is responsible for entry of adenovirus?

A

CAR (coxsackievirus and adenovirus receptor)

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11
Q

How does virion enter nucleus?

A

using hexons to interact with microtubules
(too big to get in thru pores)

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12
Q

Describe the steps for adenovirus entry

A

i) knob at end of fibre on penton bind CAR
ii) penton base bind integrin on surface
–> endocytosis
iii) virion released from endosome into cytoplasm (acidification)
iv) virion move to nucleus thru interactions between hexon and microtubules
v) virion disassembled at nuclear pore
–> DNA enter nucleus

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13
Q

Components of genes expressed by adenovirus

A

i) 6 early transcription units
ii) 2 intermediate transcription units
iii) 1 late transcription unit
iv) VA genes

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14
Q

After RNA splicing, how much mRNA is formed from late transcription unit?

A

5 (L1 to L5)

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15
Q

Features of L1 to L5

A

all have tripartite leader sequence added to them

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16
Q

What is VA gene transcribed by?

A

RNA pol III

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17
Q

Function of VA genes

A

act as microRNA

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18
Q

Function of early gene expression

A

i) induce host cells to enter S phase
ii) Defense against antiviral defense of host
iii) make viral proteins needed for DNA replication

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19
Q

Which gene is first expressed in adenovirus?

A

E1A

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20
Q

Which early genes help induce host cell to enter S phase?

A

E1A, E1B, E4

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21
Q

Which early genes help protect infected cells from antiviral defense of host?

A

E1A,B, E3,E4, VA RNA

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22
Q

which early genes make viral proteins needed for DNA replication?

A

E2 transcript

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23
Q

what cellular proteins do E1A interact with?

A

i) pRb
ii) p300, CBP histone acetyltransferase (add acetyl grp to histone tails)
iii) TBP (TATA binding protein)

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24
Q

What happens when E1A binds to pRb?

A

i) pRb dissociate from E2F
—> E2F activate expression of viral and cellular genes (e.g. viral E2) that move to S phase
ii) recruit pRb to promoter of antiviral genes –> turn them off

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25
Q

What happens if acetyl group is added to histone tail?

A

allow TFs to access the DNA

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26
Q

enzymes that add acetyl group to histone tail

A

histone acetyltransferase (HAT)

27
Q

What happens after E1A binds to p300, CBP?

A

i) E1A associate with promoters of cell cycle
ii) recruit p300/CBP to them
–> promote transcription
–> lower histone acetylation in promoters unrelated to E1A

28
Q

What happens after E1A bind TBP?

A

E1A stimulate transcription by binding of TBP
–> increased expression of early viral genes

29
Q

Target of E1B

A

one form: p53
another form: pretends to be Bcl2

30
Q

What happens after E1B bind p53?

A

i) block transcriptional activation of cell cycle inhibitors
–> induce cell cycle
ii) form complex with E4 (ubiquitin ligase)
–> degrade p53
–> lower p53 level –> prevent apoptosis

31
Q

What happens after E1B mimics Bcl2

A

it inhibits apoptosis by associating with mitochondrial membranes

32
Q

Function of E3

A
  • affect expression of cell surface receptor
  • inhibit secretion of proinflammatory stuff
    –> help infected cell acoid destruction by immune system
33
Q

Function of E4

A

i) form ubiqutin ligase with E1B –> degrade p53
ii) promote chromatin change at p53 controlled promoters (prevent p53 binding)
iii) prevent DNA repair pathways from ligating adenovirus genomes
iv) reorganize PML bodies into track like structures

34
Q

What is the function of PML bodies?

A

apoptosis, p53 activation, DNA repair

35
Q

viral proteins needed for DNA replication

A

i) pTP (preterminal protein)
ii) DNA pol
iii) ssDNA binding protein (DBP)

36
Q

cellular proteins needed for DNA replication of adenovirus

A

NFI, NFII, NFIII

37
Q

What is the origin of replication in adenovirus?

A

inverted terminal repeats at either end of genome

38
Q

What can u find in the origin of replication?

A

i) binding site for pTP, DNA pol complex
ii) binding site for NFI, II

39
Q

What is the primer for DNA replication in adenovirus?

A

dCMP (3’OH help extend DNA)

40
Q

Describe steps in DNA replication of adenovirus

A

i) pTP/Pol complex, NFI, III bind to origin
ii) dCMP covalently link to pTP
iii) dCMP hybridize to DNA template (3’OH as primer)
iv） after NFI, III leave + 2 more nts made
–> pTP shift back to end of DNA
v) nucleotide chain extends until one strand is copied
vi) displaced ssDNA used as template to make dsDNA

41
Q

proteins needed to extend one entire nucleotide chain

A

DNA pol,, DBP, NFII

42
Q

What happens to the displaced ssDNA?

A

able to form panhandle with inverted terminal repeats
–> can repeat the same replication stepsW

43
Q

When is pTP cleaved?

A

packaging of DNA into virions and converted into TP

44
Q

What recognizes tripartite leader sequence?

A

complex from E4, E1B

45
Q

How are cellular gene expression inhibited by adenovirus?

A

i) blocking the export of cellular mRNA to cytoplasm
ii) prefer translating viral mRNA over cellular ones

46
Q

How does adenovirus block the export of cellular mRNA?

A

using E1B/E4 complex
–> bind tripartite leader sequence on viral mRNA + transport out of nucleus
–> relocalize cellular proteins needed for transport to adenovirus replication (not available for cellular mRNA)

47
Q

What is targeted in cells to give preference to viral mRNA translation for adenovirus?

A

i) cellular protein kinase R (PKR)
ii) cellular translation factor EIF4F (helicase)

48
Q

How is PKR inhibited?

A

adeno VA RNA bind to PKR (prevent activation)
–> protect only translation of viral mRNA

49
Q

What is the function of cellular PKR

A

after activated in adenovirus infection
–> phosphorylate translation factor
–> inactivate translation of viral mRNA

50
Q

What inhibits eIF4F?

A

L4 inactivates it

51
Q

What happens after eIF4F is inhibited?

A

i) stop cellular mRNA translation
ii) viral one continue with presence of tripartite leader sequence

52
Q

Why can viral translation continue after eIF4F is inhibited?

A

hv tripartite leader sequence
–> ribosome can find AUG without scanning

53
Q

What is ribosome shunting?

A

finding AUG on mRNA without scanning

54
Q

what is viral precursor cleaved to form mature proteins?

A

L3

55
Q

where are hexon and pentons assembled?

A

cytoplasm

56
Q

Describe steps in virus assembly of adenovirus

A

i) hexon, pentons assembled in cytoplasm
ii) hexon, penton transported to nucleus + assembled into capsid
iii) viral DNA insert in capsid starting from packaging sequence
iv) viral precursors cleaved by L3
v) virions released from cells

57
Q

where does viral DNA start inserting into capsid?

A

packaging sequence

58
Q

what is involved in virion release of adenovirus?

A

i) cleave cytoskeleton components
– promote cell lysis
ii) accumulate E3 late in infection –> cause cell lysis
iii) apoptosis induced by E4 accumulated

59
Q

How long can adenovirus stay in host after initial infection?

A

for years

60
Q

Where does most adenovirus replicate in?

A

respiratory epithelium

61
Q

Vaccines for adenovirus?

A

type 4,7 (only for military)

62
Q

antiviral specific to adenovirus?

A

nope

63
Q

symptoms for adenovirus

A

i) pneumonia
ii) conjunctivitis
iii) kidney infection

MGY378 (13 decks)

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