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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
how are mRNAs processed in early transcription
by host cell capping, methylation, polyadenylation and (sometimes) splicing enzyme systems
26
what happens after mRNAs processed in early trasncription
then exported to the cytoplasm and translated – divide into IE and EARLY
27
what happens in Immediate Early Gene Expression in early transcription
- 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
what is E1A
transactivating transcription factor -turns on other genes
29
what happens in the Early Gene Expression: 3 goals all controlled by E1A
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
what does the DNA replication phase mark
start of the late phase
31
what does adenovirus encode in DNA replication
own DNA polymerase
32
what is the DNA replication like
continuous | no okazaki fragments
33
why is a ds structure needed for early replication of adenovirus
in order to initiate replication at the end of adenovirus = ends of the displaced single-strand is self-complementary and allows priming
34
how does priming in early replication of adenovirus occur
terminal protein
35
what is made in the late gene expression stage
production of viral capsids | Production of capsid proteins, including Fibre, penton, hexon
36
what regulates late gene expression of viral capsids
regulated by the major late promoter, from a single transcript
37
what does splicing allow in late gene expression stage
allows 18 separate mRNAs
38
what happens to the adenoviral messages in late gene expression
they are preferentially translated
39
what happens because of adenoviral messages being translated in late gene expression
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
what do all mRNAs have
tripartite leader
41
what does the mechanism of TC involve
eIF4F and eIF2a
42
what happens during virus assembly and release
- 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
what can happen when virus is released
can form inclusion bodies -the basis of persistent infections (called hidden or occult)
44
what messages are translated
Viral messages are translated while cellular messages are not
45
what were interferons discovered to do
discovered to block virus translation
46
what does the interferon receptor activate
two pathways 1. synthase from dsRNA makes ATP 2. induction of protein kinase
47
what does the IFN synthase activation pathway cause
activates ribonuclease L which causes mRNA degradation
48
what does the IFN induction of protein kinase activation pathway cause
dsRNA activates protein kinase causes eIF-2 phosphorlyation = inhibition of protein synthesis
49
when does protein synthesis occur
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
what is eIF2
eukaryotic initation factor 2
51
when is energy released in eIF2 regulation adenovirus
translate and release eIF2 into cytoplasm and no longer bound to GTP now bound to GDP as energy release
52
what is needed for another translation round
GDP must be exchanged for GTP which is done by GEF (eIF2B) | eIF GDP to GTP is changed by GEF – is reversible reaction
53
what will stop translation
if get eIF2 phosphorylation will block the GEF and block GTP recycling
54
what is responsible for the phosphorylation of eIF2
enzyme PKR is responsible for the phosphorylation of the eIF2 – causing the initation reaction to become blocked
55
what binds to PKR to prevent polymerisation
small RNA transcript – VA RNA binds to monomers of PKR to prevent polymerisation and diamerization
56
what is the VA RNA role
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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