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IMIN 324 > Smiley-4 > Flashcards

Smiley-4 Flashcards

(43 cards)

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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)

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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?

Study These Flashcards
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?

Study These Flashcards
A
  • prevents infected cell’s antiviral response
21
Q

Regular function of RB (retinoblastoma)

Study These Flashcards
A

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

22
Q

Regular function of p53

Study These Flashcards
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?

Study These Flashcards
A

blocks use of early promoter –> downregulates its own synthesis

24
Q

How does large T antigen stimulate L gene transcription?

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

- induces DNA replication that overcomes L gene Ibp suppression

25
How does large T directly initiate viral DNA replication?
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
What control does SV40 use for its regulatory strategy?
transcriptional
27
What do the E1A proteins do in adenovirus? (x3)
- bind RB - activate transcription driven from 4 other DE genes - inhibit transcription of more E1A
28
Function of E1A binding to RB protein?
push cell into S phase
29
How does E1A activate transcription from 4 DE genes?
activates cellular TFs that themselves bind DE promoters
30
How does E1A regulate its own transcription?
E1A blocks cell proteins needed for activity of E1A enhancer
31
Proteins encoded by DE (delayed early)?
E1b, E2, E3, and E4
32
Functions of the DE proteins (x3)
- evasion of host immune system - viral DNA replication - regulate late gene expression
33
DE proteins needed for antiviral defense
E1b
34
DE proteins needed for viral DNA replication
E2
35
What does E2 encode for viral DNA replication? (x3)
- viral DNAP - SSBPs - terminal proteins
36
What DE proteins transport late mRNAs from nucleus to cytoplasm?
E1b and E4
37
What DE proteins blocks transport of cellular mRNAs?
E1b and E4
38
What activates MLP (major late promoter)?
E1A
39
What is special about HSV (herpes simplex virus) DNA?
they lack introns
40
How does HSV deal with its ORFs not having introns?
makes one promoter per ORF
41
How do HSV mRNAs get transported out of nucleus without splicing?
ICP27 binds to REF and TAP as well as viral mRNAs --> serves as adaptor linking REF and TAP to mRNA
42
What is the "ticket" for mRNAs to get out of nucleus?
TAP: interacts with nuclear pore complex which leads to export of spliced mRNA
43
What proteins are on spliced mRNA that allow it to leave nucleus?
EJC (exon junction complex), TREX (which has REF) and TAP

IMIN 324 (14 decks)

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