DNA Tumor Viruses Flashcards
1
Q
What proportion of cancer cases are caused by viruses?
A
20% or 1/5 cancers
2
Q
True or False: P53 is a tumor suppressor
A
True
3
Q
True or False: P53 acts as a surveillance system for oncogenes and viral infections
A
True
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
5
Q
True or False: The p14Arf genes brinds to mdm2 protein and inhibits the degradation of P53
A
True
6
Q
True or false: P53 is mutated in more than half of all human cancers
A
True
7
Q
True or False: HPV is present in most cells of the tumor but not all of them
A
False
8
Q
True or False: Immunodeficiency is a cofactor in Lymphoproliferative disease associated with EBV
A
True
9
Q
True or False: HPV is a cofactor of cervical cancer, not the cause
A
False: its the cause
10
Q
Malaria infection causes predisposition to Merkel Cell Carcinoma (MCV)
A
False: Polyomavirus infection causes Merkel Cell carcinoma
11
Q
Which virus causes cancer in predominantly B-Cells?
A
Epstein Barr-Virus (EBV)
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.
13
Q
What cancer caused by viruses has the highest percentage of cases in women?
A
Cervix cancer
14
Q
What cancer caused by viruses has the highest percentage of cases in men?
A
Liver
15
Q
Which DNA virus causes Cervical cancer in women?
A
Papillomavirus (HPV)
16
Q
What causes liver cancer in men?
A
Hepatitis C and B
17
Q
Whats the cofactor of Cervical cancer caused by HPV?
A
Genetics
18
Q
Why do we say “the Burkitt Lymphoma belt”?
A
Theres an interplay between EBV cases and Malaria cases
19
Q
What type of cancer does Adenovirus cause?
A
None, but it has genes that a potent oncogenes
20
Q
What does Adenovirus cause?
A
Upper respiratory infection
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.
22
Q
Whats abortive infection (rodent example)
A
When you inject rodents with Adenovirus, the virus cannot replicate in the rodent cells
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
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
25
Where does the Adenovirus infect in the cell?
Nucleus
26
Whats the cythopatic effect
Adenovirus can infect epithelial cells
27
Whats the structure of the Adenovirus (3 components)
1) Protein coat
2) Fiber proteins
3) DsDNA (double stranded DNA)
28
Spikes are fiber proteins that help with...
binding to the receptors on the cells, and helps the adenovirus to get in the cells.
29
What's the Tripartite leader (TPL)
Acts like a key, enabling the virus to produce proteins it needs to survive and spread.
30
What are the early genes in Adenovirus, and what are their roles?
E1A, E1B, E3, E4 - they set up the cell for the virus to replicate
31
What are the late genes? and their role?
L1, L2, L3, L4, L5 ; structural components of the virus
32
What did Roberts and Sharp discover from DNA tumor viruses?
The existence of splicing
33
True or false: 10% of the entire genome is all you need to take a normal rodent cell to a rodent cancer cell.
True
34
Name 2 genes that can cause cancer together
E1A & E1B
35
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
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
36
E1B - includes E1B-55K and E1B-19K, whats the role of E1B-55K?
E1B-55K binds to P53, and inhibits its activity and promotes cell survival
37
How does the virus regulate its transcription?
regulates its own transcription through CR3
38
What defines the early stages of the virus
Viral DNA synthesis, once you start to get viral genome, it enters the late phase
39
What happens in the late phase?
Virus starts to make structural proteins, puts the whole virus together, and makes new copies and restarts the process
40
Is RB a tumor suppressor
yes
41
What does E2F do?
Regulator of the S phase genes, required for DNA synthesis
42
In normal conditions, whats the mechanism of Rb and E2F?
Rb binds to E2F and represses transcription
43
True or False: RB is a guardian of the G1S checkpoint in cells
True, it blocks it, but once you pass the checkpoint, the cell is committed to a cell cycle
44
E1A has 2 major roles, what are they?
Acts as a transcription factor and without E1A, the virus cant replicate
45
Why does the virus hate RB?
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
46
Mechanism of the virus
??? gets rid of ??? (sequesters it), and activation of ???? and the virus activates ????
E1A gets rid of Rb (sequesters it), and activation of S phase, and the virus activates E2f
47
How stem cells are able to replicate their DNA with Rb?
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
Mechanism with virus and Rb
Infect cells=viral protein in and takes out……??
Virus infects cells, the viral protein comes in and takes Rb out
49
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
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
What's p14Arf?
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
Whats happens when mdm2 binds to P53
degrades P53
52
When p14Arf sequesters mdm2, what happens?
It activates … and mdm2 cant degrade … anymore
Activates P53, and mdm2 cant degrade it anymore
53
When p14Arf bounds to mdm2, what happens?
P53 is stabilized and it does its tumor suppressor functions and kills the cell through cell death
54
Does P53 prevent cancer? what happens when you knockout P53 in mice?
they start to develop cancer
55
What's P53? structure?
1) binding domain
2) transactivation domain
3) C- terminal is a regulatory region
4) Site of regulation that gets phosphorylated
56
True or false: P53 binds to DNA as a tetramer and it needs that C-terminal region to form those tetramer
true
57
Whats the feedback look in normal cells for P53
1) P53 turns on Mdm2
2) mdm2 inhibits P53 and degrades it
58
If you put a genotoxic stress, what happens to the P53 pathway?
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
Why do we need E1A and E1B-55K to get cancer?
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
Whats P21? what does it do?
P21 is an inhibitor of the kinase like CDK kinases that are required to drive cell cycle
61
True or False: P21 inhibits CDK?
True
62
What happens when you have a stressor going on?
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
True or false: P53 can inhibit angiogenesis
true
64
Why dont you get cancer only with E1A? mecanism
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
To get cancer what needs to happen?
1) Deactivation of Rb
2) Prevent P53 functions
66
BCL-2
potent inhibitor of cell death
67
E1B-19K and BCL-2 roles
Both inhibit cell death
68
True or false: Bax upregulated by P53 causes cell death
True
69
Whats an oncolyte?
Trying to take a virus and engineer it so it can kiss cancer cells
70
Polyomavirus features
non-enveloped
Icosahedral
45nm in diameter
71
What is the most studied type of polyomavirus
Sv40 (Siemen virus 40)
72
true of false: Sv40 was one of the first thing sequenced
True
73
How did the vaccine for poliovirus was invented?
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
Structure of polyomavirus
Double stranded DNA
Protein capsid
75
How does the viral genome sit in polyomavirus?
Its wrapped up, in a nucleosomes, coming from the cell
76
How does polyomavirus replicate?
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
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
1 and 3
78
Whats the big contribution that polyomavirus made in cancer?
How DNA synthesis occurs in eukaryotes
79
What are the typical components of a human virus (3)?
1- RR - regulatory region
2- Early genes made first
3- Late genes that form the capsids
80
Which gene in SV40 causes cancer?
Large Tumor Antigen (LgT) - in rodents that have tumors caused by SV40, they carry that antigen
81
Whats the similarity of LgT (polyomavirus) and E1A-E1B-55K (Adenovirus)
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
Papillomavirus is similar to Polyomavirus, what are the features?
non-enveloped, icosahedral
83
True or False: papillomavirus is a huge driver of cervical cancer
True
84
why is cervical cancer preventable in high income countries
Screening and vaccine
85
True or False: the biggest cause of cancer mortality is cervical cancer in low income countries
True (screening)
86
What did Hausen discover
made the molecular link between cervical cancer and HPV
87
What did Henrietta Lacks do for biomedical research?
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
What is one abnormality that HPV causes
Skin abnormality
89
How was the HPV vaccine developped?
Took the capsid protein from papillomavirus and targeted 16 and 18 made recombinant L1 and purified it
90
Even if 35 HPV is a high risk for cervical cancer.. why wasnt it used?
Because low cases in Western countries... but 10% of cervical cancer in Africa...
no investment for Western countries (they dont care lol)
91
Why is it difficult to study HPV in vitro?
Infects epithelial cells of the skin - replicating these tissues in vitro in hard, limiting the study of the virus's natural behavior
92
How does HPV infect skin cells?
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
How effective is the Pap test for screening HPV?
80%
94
How does Pap test work
Swap of the cervix
Look for abnormalities
Cells with large nucleus
Only in high income countries
95
True or false: Papilloma virus infection is the most common sexually transmitted infection in the world
True
96
Mecanism of progression of HPV
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
How long does it take from the infection to cervical cancer
Decades
98
Which part (pieces) of the viral HPV genome that integrates in cervical cancer?
L1 protein
E6 and E7 genes
99
Whats the role of E6
inhibits apoptosis of infected cells
100
Whats the role of E7
Stimulate DNA synthesis in infected cells
101
Role of L1 protein
Viral Capsid protein
102
Mecanism of HPV E7
1) E7 binds to Rb
2) Sequesters Rb
3) turns on E2F
4) Turns on S phase gene
5) virus can replicate DNA
103
SV40 LgT, E7, E1A, what motif is there in the binding region of these oncogenes
L-X-C-X-E
104
SV40 Lgt, E1A and E7 all have the same mecanism... what is it
1) turns on S phase through binding in pocket protein
2) sequesters Rb turns on E2F
3) Turn on S phase innapropriately
105
How does E7 induce apoptosis?
E7 turns on P53 and causes apoptosis
106
E7+E6 mechanism
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
2 ways to cause cell cycle progression
1) getting rid of Rb
2) getting rid of P53
108
Rb binds to which genes in Polyomavirus, Adenovirus, and Papillomavirus?
Polyomavirus - SV40 Lgt
Adenovirus - E1A
Papillomavirus - E7
109
P53 binds to which genes in Polyomavirus, Adenovirus, and Papillomavirus?
Polyomavirus - SV40 Lgt
Adenovirus - E1B
Papillomavirus - E6 and E6AP complex
110
True or False: EBV is a more complex ADN virus than the 3 others
True, enveloped, 180kb
111
EBV causes different types of cancer... two of them is immunodeficient (cofactors)... which one
Nasopharyngeal cancer, Lymphoproliferative
112
EBV is a cofactor with Malaria .. which disease do they cause
Brukitts lymphoma
112
Which disease is Genetic with EBV DNA virus
Cervical cancer
Hodgkins Lymphoma
113
Stages of infection of EBV
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
How is EBV structure different from Adenovirus, papillomavirus, and polyomavirus
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
Gamma A globulemia, what happens with this genetic mutation
People with this mutation do not have B cells and wont have EBV
114
How does EBV cause cell proliferation
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!
