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IMIN 324 > Smiley-4 > Flashcards

Smiley-4 Flashcards

1
Q

What do DNA viruses use to replicate their genome and transcribe it?

A
  • DNA-dependent DNAP

- DNAdRNAP

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2
Q

What is the trend is virus size and using host molecules?

A

Small viruses are more likely rely on host mechanisms than larger ones

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3
Q

What is the challenge of DNA viruses in animal cells?

A

Animal cells only have a lot of dNTPs and enzymes for DNA replication when they are actively replicating

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4
Q

What phase are most animal cells in?

A

G0

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5
Q

What phase does a DNA virus want an animal cell to be in?

A

S phase

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6
Q

Why is there lower mutation rate in DNA viruses?

A

DNAP has proofreading ability

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7
Q

Function of early genes

A

encode non-structural protein

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8
Q

Function of early proteins (x3)

A
  • activate viral gene expression
  • promoter viral DNA replication
  • evade host antiviral defense
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9
Q

When are late genes expressed?

A

After DNA replication has begun

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10
Q

What do L genes usually encode?

A

components of virion

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11
Q

Function of immediate early (IE) proteins

A

Regulatory roles

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12
Q

Function of delayed early (DE) proteins

A

enzymes and other proteins involved in viral DNA replication

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13
Q

Where do DNA viruses replicate their genome?

A

nucleus of host cell

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14
Q

Which ORF is recognized by eukaroytic ribosomes?

A

Only ORF closest to 5’ end

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15
Q

What represses late genes of SV40 from being expressed?

A

Ibp

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16
Q

What proteins the 2 early mRNAs encode?

A

small T and large T antigen

- T = tumor

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17
Q

Which T antigen is important for viral replication?

A

Large T

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18
Q

Functions of Large T antigen? (x5)

A
  • pushes cell to S phase
  • inactivates p53
  • binds to 3 sites in intergenic (ori) region
  • stimulates L gene transcription
  • initiate viral DNA replication
19
Q

How does large T antigen push cell to S phase?

A
  • binds RB which blocks cell in G1 phase –> cell goes to S phase
20
Q

What does binding of p53 by large T antigen do?

A
  • prevents infected cell’s antiviral response
21
Q

Regular function of RB (retinoblastoma)

A

tumor suppression protein that keeps cell in mid-G1 of its cycle

22
Q

Regular function of p53

A
  • detects signs of virus infection and other stresses

- when engaged, it tells cell to stop at G1 or commit suicide

23
Q

Reason for large T antigen binding to 3 sites in intergenic region?

A

blocks use of early promoter –> downregulates its own synthesis

24
Q

How does large T antigen stimulate L gene transcription?

A
  • binds to ori –> direct activator of late promoter

- induces DNA replication that overcomes L gene Ibp suppression

25
Q

How does large T directly initiate viral DNA replication?

A

unwinds DNA at ori and recruits replication host machinery –> amount of DNA made exceeds number of Ibp in cell so more L genes can be made

26
Q

What control does SV40 use for its regulatory strategy?

A

transcriptional

27
Q

What do the E1A proteins do in adenovirus? (x3)

A
  • bind RB
  • activate transcription driven from 4 other DE genes
  • inhibit transcription of more E1A
28
Q

Function of E1A binding to RB protein?

A

push cell into S phase

29
Q

How does E1A activate transcription from 4 DE genes?

A

activates cellular TFs that themselves bind DE promoters

30
Q

How does E1A regulate its own transcription?

A

E1A blocks cell proteins needed for activity of E1A enhancer

31
Q

Proteins encoded by DE (delayed early)?

A

E1b, E2, E3, and E4

32
Q

Functions of the DE proteins (x3)

A
  • evasion of host immune system
  • viral DNA replication
  • regulate late gene expression
33
Q

DE proteins needed for antiviral defense

A

E1b

34
Q

DE proteins needed for viral DNA replication

A

E2

35
Q

What does E2 encode for viral DNA replication? (x3)

A
  • viral DNAP
  • SSBPs
  • terminal proteins
36
Q

What DE proteins transport late mRNAs from nucleus to cytoplasm?

A

E1b and E4

37
Q

What DE proteins blocks transport of cellular mRNAs?

A

E1b and E4

38
Q

What activates MLP (major late promoter)?

A

E1A

39
Q

What is special about HSV (herpes simplex virus) DNA?

A

they lack introns

40
Q

How does HSV deal with its ORFs not having introns?

A

makes one promoter per ORF

41
Q

How do HSV mRNAs get transported out of nucleus without splicing?

A

ICP27 binds to REF and TAP as well as viral mRNAs –> serves as adaptor linking REF and TAP to mRNA

42
Q

What is the “ticket” for mRNAs to get out of nucleus?

A

TAP: interacts with nuclear pore complex which leads to export of spliced mRNA

43
Q

What proteins are on spliced mRNA that allow it to leave nucleus?

A

EJC (exon junction complex), TREX (which has REF) and TAP

IMIN 324 (14 decks)

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