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Midterm 504 > DNA Tumor Viruses > Flashcards

DNA Tumor Viruses Flashcards

1
Q

What proportion of cancer cases are caused by viruses?

A

20% or 1/5 cancers

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2
Q

True or False: P53 is a tumor suppressor

A

True

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3
Q

True or False: P53 acts as a surveillance system for oncogenes and viral infections

A

True

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4
Q

True or False: When HPV E7 protein induces E2F activity, this also results increased transcription of p14Arf gene, which leads to P53 degradation and apoptosis.

A

False: Increased transcription of p14Arf gene leads to the stabilization of P53, not its degradation

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5
Q

True or False: The p14Arf genes brinds to mdm2 protein and inhibits the degradation of P53

A

True

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6
Q

True or false: P53 is mutated in more than half of all human cancers

A

True

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7
Q

True or False: HPV is present in most cells of the tumor but not all of them

A

False

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8
Q

True or False: Immunodeficiency is a cofactor in Lymphoproliferative disease associated with EBV

A

True

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9
Q

True or False: HPV is a cofactor of cervical cancer, not the cause

A

False: its the cause

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10
Q

Malaria infection causes predisposition to Merkel Cell Carcinoma (MCV)

A

False: Polyomavirus infection causes Merkel Cell carcinoma

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11
Q

Which virus causes cancer in predominantly B-Cells?

A

Epstein Barr-Virus (EBV)

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12
Q

How do DNA viruses cause cancer and replicate?

A

Viruses infect cells but since most of the cells are not dividing (quiescent state), they’re terminally differentiated… The DNA viruses make the cell they’ve infected start to make DNA, so pushes them back in the cell cycle. The cells start replicating and cause cancer.

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13
Q

What cancer caused by viruses has the highest percentage of cases in women?

A

Cervix cancer

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14
Q

What cancer caused by viruses has the highest percentage of cases in men?

A

Liver

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15
Q

Which DNA virus causes Cervical cancer in women?

A

Papillomavirus (HPV)

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16
Q

What causes liver cancer in men?

A

Hepatitis C and B

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17
Q

Whats the cofactor of Cervical cancer caused by HPV?

A

Genetics

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18
Q

Why do we say “the Burkitt Lymphoma belt”?

A

Theres an interplay between EBV cases and Malaria cases

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19
Q

What type of cancer does Adenovirus cause?

A

None, but it has genes that a potent oncogenes

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20
Q

What does Adenovirus cause?

A

Upper respiratory infection

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21
Q

Why did Adenovirus become intensively studied?

A

It became a model for Cancer biology…they isolated the virus and purified it, and injected rodents: rodents came down with cancer/developed tumors.

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22
Q

Whats abortive infection (rodent example)

A

When you inject rodents with Adenovirus, the virus cannot replicate in the rodent cells

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23
Q

Whats the mechanisme of Adenovirus (in rodents)…hint: 4 steps

A

1) Adenovirus delivers its genome to the rodent cells
2) Theres a block of DNA replication
3) Incompability with the viral machinery
4) Viral genome delivered, which give cancer to rodents

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24
Q

Explain why Adenovirus doesn’t work in humans?

A

1 - the virus replicates very well, so by infecting cells, the cells die
2 - Humans are good at mounting an immune response to Adenovirus

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25
Q

Where does the Adenovirus infect in the cell?

A

Nucleus

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26
Q

Whats the cythopatic effect

A

Adenovirus can infect epithelial cells

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27
Q

Whats the structure of the Adenovirus (3 components)

A

1) Protein coat
2) Fiber proteins
3) DsDNA (double stranded DNA)

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28
Q

Spikes are fiber proteins that help with…

A

binding to the receptors on the cells, and helps the adenovirus to get in the cells.

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29
Q

What’s the Tripartite leader (TPL)

A

Acts like a key, enabling the virus to produce proteins it needs to survive and spread.

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30
Q

What are the early genes in Adenovirus, and what are their roles?

A

E1A, E1B, E3, E4 - they set up the cell for the virus to replicate

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31
Q

What are the late genes? and their role?

A

L1, L2, L3, L4, L5 ; structural components of the virus

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32
Q

What did Roberts and Sharp discover from DNA tumor viruses?

A

The existence of splicing

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33
Q

True or false: 10% of the entire genome is all you need to take a normal rodent cell to a rodent cancer cell.

A

True

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34
Q

Name 2 genes that can cause cancer together

A

E1A & E1B

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35
Q

What does E1A do?

E1A is the ??? gene that the virus makes

Rb binds to ???? and activates E2F

stimulate ???? , causing G0-arrested cells to enter the S-phase programme

A

E1A is the first gene that the virus makes

Rb binds to E1A and activates E2F

stimulate DNA synthesis, causing G0-arrested cells to enter the S-phase programme

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36
Q

E1B - includes E1B-55K and E1B-19K, whats the role of E1B-55K?

A

E1B-55K binds to P53, and inhibits its activity and promotes cell survival

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37
Q

How does the virus regulate its transcription?

A

regulates its own transcription through CR3

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38
Q

What defines the early stages of the virus

A

Viral DNA synthesis, once you start to get viral genome, it enters the late phase

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39
Q

What happens in the late phase?

A

Virus starts to make structural proteins, puts the whole virus together, and makes new copies and restarts the process

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40
Q

Is RB a tumor suppressor

A

yes

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41
Q

What does E2F do?

A

Regulator of the S phase genes, required for DNA synthesis

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42
Q

In normal conditions, whats the mechanism of Rb and E2F?

A

Rb binds to E2F and represses transcription

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43
Q

True or False: RB is a guardian of the G1S checkpoint in cells

A

True, it blocks it, but once you pass the checkpoint, the cell is committed to a cell cycle

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44
Q

E1A has 2 major roles, what are they?

A

Acts as a transcription factor and without E1A, the virus cant replicate

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45
Q

Why does the virus hate RB?

A

Because its preventing those S phase genes that encode the DNA polymerase, required for nucleotide biosynthesis. The virus needs to get nucleotide pools increased to get its own DNA replication

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46
Q

Mechanism of the virus

??? gets rid of ??? (sequesters it), and activation of ???? and the virus activates ????

A

E1A gets rid of Rb (sequesters it), and activation of S phase, and the virus activates E2f

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47
Q

How stem cells are able to replicate their DNA with Rb?

A

CDK phosphorylate Rb, and Rb comes off of E2F, you get a pulse of S phase genes, the cells progress through S phase and rb gets phosphorylated again (normal cell cycles

48
Q

Mechanism with virus and Rb
Infect cells=viral protein in and takes out……??

A

Virus infects cells, the viral protein comes in and takes Rb out

49
Q

Do you need E1A and E1B for tumor formation? why?

Hint; adenovirus attaches to host cell, viral DNA enters the nucleus and … is expressed and binds to ….
E1A dusrupts cell cycle and promotes cell division
E1b is expressed and binds to … and …

Its prevents… by degrading … and its function
E1b supports efficient viral DNA replication

A

adenovirus attaches to host cell, viral DNA enters the nucleus and E1A is expressed and binds to RB
E1A dusrupts cell cycle and promotes cell division
E1b is expressed and binds to E1A and P53
Its prevents apoptosis by degrading P53 and its function
E1b supports efficient viral DNA replication

50
Q

What’s p14Arf?

A

1) Tumor suppressor for other cancers that are not driven by viruses
2) Often methylated in silence = not expressed
3) moves to the nucleus and binds to mdm2
4) mdm2 binds to P53

51
Q

Whats happens when mdm2 binds to P53

A

degrades P53

52
Q

When p14Arf sequesters mdm2, what happens?

It activates … and mdm2 cant degrade … anymore

A

Activates P53, and mdm2 cant degrade it anymore

53
Q

When p14Arf bounds to mdm2, what happens?

A

P53 is stabilized and it does its tumor suppressor functions and kills the cell through cell death

54
Q

Does P53 prevent cancer? what happens when you knockout P53 in mice?

A

they start to develop cancer

55
Q

What’s P53? structure?

A

1) binding domain
2) transactivation domain
3) C- terminal is a regulatory region
4) Site of regulation that gets phosphorylated

56
Q

True or false: P53 binds to DNA as a tetramer and it needs that C-terminal region to form those tetramer

A

true

57
Q

Whats the feedback look in normal cells for P53

A

1) P53 turns on Mdm2
2) mdm2 inhibits P53 and degrades it

58
Q

If you put a genotoxic stress, what happens to the P53 pathway?

A

1) The post-translational modifications of P53 make it resistant to mdm2
2) Also p14Arf through these oncogenes can inhibit mdm2 function and P53 is stabilized and gets turned on
3) P53 acts as a transcription factor

59
Q

Why do we need E1A and E1B-55K to get cancer?

A

E1A’s Role:

E1A disrupts the cell’s natural “stop signs” that regulate cell growth, allowing the cell to keep dividing.
E1B-55K’s Role:

E1B-55K prevents the cell from self-destructing, even when there are problems inside it.
Working Together:

E1A and E1B-55K team up to make cells grow uncontrollably and avoid natural cell death

60
Q

Whats P21? what does it do?

A

P21 is an inhibitor of the kinase like CDK kinases that are required to drive cell cycle

61
Q

True or False: P21 inhibits CDK?

A

True

62
Q

What happens when you have a stressor going on?

A

1) P53 stops the cell cycle
2) P53 turns on genes for DNA repair
3) P53 senses when cell is being compromised, because of mutations , or through the expression of viral oncogenes. When ythat happens, it can also turn on genes that cause cell death (Bax Fas)

63
Q

True or false: P53 can inhibit angiogenesis

A

true

64
Q

Why dont you get cancer only with E1A? mecanism

A

1) E1A expressed in cells
2) turns on p53 pathway
3) through p14Arf, binds to Rb
4) turns on E2F
5) P14Arf levels go up
6) P53 gets stabilized and causes cell death
7) E1B-55K binds to P53 and inhibits it to take it out of the equation

65
Q

To get cancer what needs to happen?

A

1) Deactivation of Rb
2) Prevent P53 functions

66
Q

BCL-2

A

potent inhibitor of cell death

67
Q

E1B-19K and BCL-2 roles

A

Both inhibit cell death

68
Q

True or false: Bax upregulated by P53 causes cell death

A

True

69
Q

Whats an oncolyte?

A

Trying to take a virus and engineer it so it can kiss cancer cells

70
Q

Polyomavirus features

A

non-enveloped
Icosahedral
45nm in diameter

71
Q

What is the most studied type of polyomavirus

A

Sv40 (Siemen virus 40)

72
Q

true of false: Sv40 was one of the first thing sequenced

A

True

73
Q

How did the vaccine for poliovirus was invented?

A

1) they looked at kidney cells from monkeys
2) They cultured the cells
3) grew poliovirus on these cells
4) They collecyed the virus in the supernatant and used it as a vaccine by inactivating the virus with formalin
5) Couple of years later, they started seeing virus replicating, it was polyomavirus. So the monkeys has the Sv40 virus. They then injected the Sv40 in rodents and saw cancer

74
Q

Structure of polyomavirus

A

Double stranded DNA
Protein capsid

75
Q

How does the viral genome sit in polyomavirus?

A

Its wrapped up, in a nucleosomes, coming from the cell

76
Q

How does polyomavirus replicate?

A

The virus steals nucleosomes from the cells that it infects…
The way the virus replicates its DNA is using all the same enzymes that our normal DNA uses to replicate DNA

77
Q

Which of the following statements are true concerning HPV induced pathologies in humans

  1. Cervical cancer caused by HPV takes many years to develop after the initial viral
    infection.
  2. The HPV types 16 and 18 account for only 5% of all cervical cancers.
  3. The vast majority of HPV infections cause no symptoms or only benign lesions (i.e.
    warts) that resolve within several weeks.
  4. Conventional PAP tests involve examination of stained cervical cells for abnormalities
    and reaches a sensitivity of 95%
  5. The HPV E3 gene product stimulates DNA synthesis in an infected cell

A. 1 and 3.
B. 1, 3 and 4.
C. 2 and 4.
D. 1, 2 and 5.
E. All of the above

A

1 and 3

78
Q

Whats the big contribution that polyomavirus made in cancer?

A

How DNA synthesis occurs in eukaryotes

79
Q

What are the typical components of a human virus (3)?

A

1- RR - regulatory region
2- Early genes made first
3- Late genes that form the capsids

80
Q

Which gene in SV40 causes cancer?

A

Large Tumor Antigen (LgT) - in rodents that have tumors caused by SV40, they carry that antigen

81
Q

Whats the similarity of LgT (polyomavirus) and E1A-E1B-55K (Adenovirus)

A

E1A binds to Rb, allows the cell to enter S phase, where DNA replication occurs, and leads to uncontrolled cell division.. Meanwhile, E1B-55K binds and inactivated tumor suppressor P53, and prevent the cells tp apoptosis

LgT inactivate Rb, bypasses G1 Checkpoint and enter Sphase

LgT inactivate P53 disrupts stabilizing effect of p14Arf, and ensure that cells dont go apoptosis

82
Q

Papillomavirus is similar to Polyomavirus, what are the features?

A

non-enveloped, icosahedral

83
Q

True or False: papillomavirus is a huge driver of cervical cancer

A

True

84
Q

why is cervical cancer preventable in high income countries

A

Screening and vaccine

85
Q

True or False: the biggest cause of cancer mortality is cervical cancer in low income countries

A

True (screening)

86
Q

What did Hausen discover

A

made the molecular link between cervical cancer and HPV

87
Q

What did Henrietta Lacks do for biomedical research?

A

She had an aggressive cervical cancer, but gave her cells to be plated.

HeLa cells express the viral oncogene, they have DNA from HPV

88
Q

What is one abnormality that HPV causes

A

Skin abnormality

89
Q

How was the HPV vaccine developped?

A

Took the capsid protein from papillomavirus and targeted 16 and 18 made recombinant L1 and purified it

90
Q

Even if 35 HPV is a high risk for cervical cancer.. why wasnt it used?

A

Because low cases in Western countries… but 10% of cervical cancer in Africa…
no investment for Western countries (they dont care lol)

91
Q

Why is it difficult to study HPV in vitro?

A

Infects epithelial cells of the skin - replicating these tissues in vitro in hard, limiting the study of the virus’s natural behavior

92
Q

How does HPV infect skin cells?

A

1) Comes from microlesions in the skin
2) HPV gets in
3) Needs to infects the basal layers of the cells (constantly dividing slowly)
4) As the cells differentiare, it regulates expression of early genes
5) late genes gets turned on
6) virus gets to the top and start to release more virus at the surface

93
Q

How effective is the Pap test for screening HPV?

A

80%

94
Q

How does Pap test work

A

Swap of the cervix
Look for abnormalities
Cells with large nucleus
Only in high income countries

95
Q

True or false: Papilloma virus infection is the most common sexually transmitted infection in the world

A

True

96
Q

Mecanism of progression of HPV

A

1) Infects basal layer
2) If immune system takes care of it, the infection is resolved
3) 10-20% of cases : the virus persists and the virus goes undetected ; becomes carcinoma

97
Q

How long does it take from the infection to cervical cancer

A

Decades

98
Q

Which part (pieces) of the viral HPV genome that integrates in cervical cancer?

A

L1 protein
E6 and E7 genes

99
Q

Whats the role of E6

A

inhibits apoptosis of infected cells

100
Q

Whats the role of E7

A

Stimulate DNA synthesis in infected cells

101
Q

Role of L1 protein

A

Viral Capsid protein

102
Q

Mecanism of HPV E7

A

1) E7 binds to Rb
2) Sequesters Rb
3) turns on E2F
4) Turns on S phase gene
5) virus can replicate DNA

103
Q

SV40 LgT, E7, E1A, what motif is there in the binding region of these oncogenes

A

L-X-C-X-E

104
Q

SV40 Lgt, E1A and E7 all have the same mecanism… what is it

A

1) turns on S phase through binding in pocket protein
2) sequesters Rb turns on E2F
3) Turn on S phase innapropriately

105
Q

How does E7 induce apoptosis?

A

E7 turns on P53 and causes apoptosis

106
Q

E7+E6 mechanism

A

E6 binds to P53 and degrades it
E6AP is a ubiquitin ligase so targets proteins to degrade them

E7 bind to rb = uncontrolled growth

107
Q

2 ways to cause cell cycle progression

A

1) getting rid of Rb
2) getting rid of P53

108
Q

Rb binds to which genes in Polyomavirus, Adenovirus, and Papillomavirus?

A

Polyomavirus - SV40 Lgt
Adenovirus - E1A
Papillomavirus - E7

109
Q

P53 binds to which genes in Polyomavirus, Adenovirus, and Papillomavirus?

A

Polyomavirus - SV40 Lgt
Adenovirus - E1B
Papillomavirus - E6 and E6AP complex

110
Q

True or False: EBV is a more complex ADN virus than the 3 others

A

True, enveloped, 180kb

111
Q

EBV causes different types of cancer… two of them is immunodeficient (cofactors)… which one

A

Nasopharyngeal cancer, Lymphoproliferative

112
Q

EBV is a cofactor with Malaria .. which disease do they cause

A

Brukitts lymphoma

112
Q

Which disease is Genetic with EBV DNA virus

A

Cervical cancer
Hodgkins Lymphoma

113
Q

Stages of infection of EBV

A

1) infects the oral epithelial cells in mouth
2) makes more viral particles
3) infects B cells only
4) Keeps genome in place, divides alone with B cells and stays forever

113
Q

How is EBV structure different from Adenovirus, papillomavirus, and polyomavirus

A

EBV is enveloped
Lipid membrane around the capsid with double stranded DNA, and glycoproteins that attach to cells

The others are non enveloped, have a capsid, DsDNA
Papillomavirus and polyomavirus dont have lipid envelope, but adenovirus has fiber proteins to attach to cells

113
Q

Gamma A globulemia, what happens with this genetic mutation

A

People with this mutation do not have B cells and wont have EBV

114
Q

How does EBV cause cell proliferation

A

LMP1 mimics CD40 and cause cells to proliferte
CD40 turns on N-kappaB
LMP2A mimics the function of B cell receptor
EBV infects B cells!

Midterm 504 (5 decks)

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