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Virology > 11 Adenovirus > Flashcards

11 Adenovirus Flashcards

1
Q

what does matadenovirus infect

A

mammals, Species Human Adenovirus type C

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2
Q

what does aviadenovirus infect

A

birds

species fowl adenovirus A

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3
Q

what species is atadenovirus

A

ovine adenovirus

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4
Q

what species is siadenovirus

A

species frog adenovirus

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5
Q

what species if ichtadenovirus

A

sturgeon adenovirus A

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6
Q

where is human adenovirus - mastadenovirus frequently occuring

A

frequent cause of acute upper respiratory tract (URT) infections
responsible for 5-10% of the common cold

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7
Q

what does human adenovirus cause

A

cause epidemics, especially in military recruits

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8
Q

where does human adenovirus replicate

A

adenoid tissue

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9
Q

what is the therapy

A

Vaccine normally only given to military recruits to prevent epidemic spread
Risk to general population is low

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10
Q

why might adenoviruses be useful

A

easily manipulated and can have been used as viral vectors, for human gene transfer

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11
Q

what are adenoviruses used to study

A

transcription and translational control

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12
Q

what is the morphology of adenovirus

A

icosahedral

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13
Q

what is the shell of adenovirus like

A 
composed of 252 units of which:
240 hexons (each with 6 neighbours)
12 pentons (each with 5 neighbours)
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14
Q

what is the adenovirus genome like

A

Linear, non-segmented, d/s DNA

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15
Q

where does the synthesis of genes occur in adenoviruses

A

on the l or leftward strand and also r the rightward strand

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16
Q

what process makes the products in adenovirus genome

A

Multiple products are made from each using a process called splicing-which was first discovered in adenovirus

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17
Q

what are the phases of expression in adenoviruses

A

immediate early (IE-E1A)
early (E) DNA replication
Late (L) gene expression

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18
Q

what occurs in adenovirus splicing

A

Adenovirus uses several splice donor and acceptor sites to allow multiple proteins to be made from a single gene-see across

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19
Q

what are the stages in adenovirus life cycle

A
  1. Attachment
  2. Penetration and Uncoating
  3. Early transcription
  4. DNA Replication (early replication of adenovirus)
  5. Late gene expression, production of viral capsids
  6. Virus assembly and release
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20
Q

what happens in the attachment stage

A

Fiber binds cellular receptor, CAR penton base binds integrins (internalization)

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21
Q

what mediates the penetration and uncoating stage

A

pentons which trigger phagocytosis into a phagocytic vacule

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22
Q

what happens in lysis of the penetration and uncoating stage

A

lysis then occurs releasing a spherical partially uncoated partial- pentons are released

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23
Q

what happens when the hexon protein is released in penetration and uncoating

A

Hexon protein are released and the viral core enters the nucleus through nuclear pores

24
Q

what does adenovirus use in early transcription

A

Adenovirus uses host cell RNA polymerase and early mRNAs are transcribed from scattered regions of both strands

25
Q

how are mRNAs processed in early transcription

A

by host cell capping, methylation, polyadenylation and (sometimes) splicing enzyme systems

26
Q

what happens after mRNAs processed in early trasncription

A

then exported to the cytoplasm and translated – divide into IE and EARLY

27
Q

what happens in Immediate Early Gene Expression in early transcription

A
  • Transcription of the E1A gene- multiply spliced
  • E1A works by interacting with other proteins not by DNA binding
  • Necessary for transcription of all early genes and in general activation of the genome
28
Q

what is E1A

A

transactivating transcription factor -turns on other genes

29
Q

what happens in the Early Gene Expression: 3 goals all controlled by E1A

A
  1. induction of cells to enter S (synthesis) phase of the cell cycle providing an optimal environment for DNA replication E1A-E4
  2. synthesising gene products needed for DNA replication encoded by E2
  3. expression of genes involved in combating antiviral defenses
30
Q

what does the DNA replication phase mark

A

start of the late phase

31
Q

what does adenovirus encode in DNA replication

A

own DNA polymerase

32
Q

what is the DNA replication like

A

continuous

no okazaki fragments

33
Q

why is a ds structure needed for early replication of adenovirus

A

in order to initiate replication at the end of adenovirus = ends of the displaced single-strand is self-complementary and allows priming

34
Q

how does priming in early replication of adenovirus occur

A

terminal protein

35
Q

what is made in the late gene expression stage

A

production of viral capsids

Production of capsid proteins, including Fibre, penton, hexon

36
Q

what regulates late gene expression of viral capsids

A

regulated by the major late promoter, from a single transcript

37
Q

what does splicing allow in late gene expression stage

A

allows 18 separate mRNAs

38
Q

what happens to the adenoviral messages in late gene expression

A

they are preferentially translated

39
Q

what happens because of adenoviral messages being translated in late gene expression

A

it is translated at the expense of cellular message (cell is processing viral RNA over and above the host RNA) cellular message isn’t translated (host cell shut off)

40
Q

what do all mRNAs have

A

tripartite leader

41
Q

what does the mechanism of TC involve

A

eIF4F and eIF2a

42
Q

what happens during virus assembly and release

A
  • Empty Capsid proteins are assembled
  • The viral DNA then enters the capsid via a packaging signal near the left side of the genome which binds to one or more capsid proteins
  • Eventually lysis of the cell occurs and up to 1000 viruses are released per infected cell
43
Q

what can happen when virus is released

A

can form inclusion bodies -the basis of persistent infections (called hidden or occult)

44
Q

what messages are translated

A

Viral messages are translated while cellular messages are not

45
Q

what were interferons discovered to do

A

discovered to block virus translation

46
Q

what does the interferon receptor activate

A

two pathways

  1. synthase from dsRNA makes ATP
  2. induction of protein kinase
47
Q

what does the IFN synthase activation pathway cause

A

activates ribonuclease L which causes mRNA degradation

48
Q

what does the IFN induction of protein kinase activation pathway cause

A

dsRNA activates protein kinase causes eIF-2 phosphorlyation = inhibition of protein synthesis

49
Q

when does protein synthesis occur

A

when eIF2, GTP and initator TRNA methionine in a complex forming the ternary complex – goes to the end of the RNA together with cap binding proteins – the eIF-4F bind to the cap and look for the correct AUG where it will start translation

50
Q

what is eIF2

A

eukaryotic initation factor 2

51
Q

when is energy released in eIF2 regulation adenovirus

A

translate and release eIF2 into cytoplasm and no longer bound to GTP now bound to GDP as energy release

52
Q

what is needed for another translation round

A

GDP must be exchanged for GTP which is done by GEF (eIF2B)

eIF GDP to GTP is changed by GEF – is reversible reaction

53
Q

what will stop translation

A

if get eIF2 phosphorylation will block the GEF and block GTP recycling

54
Q

what is responsible for the phosphorylation of eIF2

A

enzyme PKR is responsible for the phosphorylation of the eIF2 – causing the initation reaction to become blocked

55
Q

what binds to PKR to prevent polymerisation

A

small RNA transcript – VA RNA binds to monomers of PKR to prevent polymerisation and diamerization

56
Q

what is the VA RNA role

A

block the activation of PKR by dsRNA thereby preventing the block in protein synthesis which would occur in it absence

Virology (15 decks)

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