Oncogenic Viruses

Question 1

Which 4 gene types are damaged during oncogenesis?

Answer 1

Proto-oncogenes, tumour suppressor genes, regulating apoptosis, DNA repair

Question 2

What are the oncogenic RNA viruses?

Answer 2

Oncoretroviruses

Question 3

What are the oncogenic DNA viruses?

Answer 3

Papillomaviruses, herpesviruses

Question 4

Which types of viruses cause leukaemias and lymphomas?

Answer 4

The alpha, beta, gamma, delta and epsilon viruses

Question 5

What type of virus is HIV?

Answer 5

Lentivirus

Question 6

Which species are affected by the alpha, beta, gamma, delta and epsilon viruses?

Answer 6

All veterinary

Question 7

Why do retroviruses need close or blood contact?

Answer 7

Enveloped and unstable

Question 8

What is the genome like in retroviruses?

Answer 8

ss +ve sense RNA with terminal repeat elements

Question 9

Which type of virus has gag pol and env?

Answer 9

Retrovirus

Question 10

What does gag do?

Answer 10

Structural

Question 11

What does pol do?

Answer 11

Repliation enzymes

Question 12

What does env do?

Answer 12

The envelopes

Question 13

What happens to the DNA provirus in retroviruses?

Answer 13

Integrates into the host genome

Question 14

What do the LTR of a retrovirus contain?

Answer 14

Enhancer elements

Question 15

What can some acutely oncogenic viruses replace env with?

Answer 15

A host oncogene

Question 16

What happens if you replace env with a host oncogene?

Answer 16

Replication defective

Question 17

How can you become acutely oncogenic whilst remaining replication competent?

Answer 17

Just add and oncogene

Question 18

What is the genome like in replication competent but weakly oncogenic viruses?

Answer 18

They have gag, pol and env with accessory ORFs which act as oncoproteins

Question 19

Why can oncogenic retroviruses only affect replicating cells e.g. lymphoid, haematopoietic?

Answer 19

Can’t enter the nuclear membrane so the pre-integration complex must wait until cell division

Question 20

How are exogenous viruses transmitted?

Answer 20

Horizontal

Question 21

How are endogenous viruses transmitted?

Answer 21

Provirus in germline so vertical transmission

Question 22

How do some viruses encode v-onc?

Answer 22

Pick up a proto-oncogene and lose env/pol (take a highly active oncogene into the host cell)

Question 23

Which mutations can v-onc contain affecting proteins?

Answer 23

Alter normal protein function or regulation e.g. increase stability or cause constitutive activation

Question 24

What happens if v-onc fuses to gag?

Answer 24

Transports the oncoprotein to the cell membrane where it functions as a signal transporter.

Question 25

What is expression of v-onc like?

Answer 25

Not controlled as viral LTRs are strong and not affected by cellular regulation.

Question 26

What is replication like in viruses encoding v-onc?

Answer 26

Usually defective but can be competent.

Question 27

How do you get cis-activation of a cellular oncogene?

Answer 27

Provirus inserts close to c-onc and LTR acts as a promoter or enhancer

Question 28

What is replication and oncogenesis like in cis-activation of a cellular oncogene?

Answer 28

Weakly oncogenic and won't transform in vitro, but competent for replication

Question 29

Why are tumours clonal in cis-activation of a cellular oncogene?

Answer 29

The cells all have one preferred integration site

Question 30

What is replication and oncogenesis like in trans-activation by an essential virus protein?

Answer 30

Weakly oncogenic, long incubation, replication competent

Question 31

Are the tumours clonal in in trans-activation by an essential virus protein?

Answer 31

Yes, but there is no preferred integration site

Question 32

What clinical signs are papillomaviridae assocaited with?

Answer 32

Warts

Question 33

Can you culture papillomavirus?

Answer 33

No

Question 34

Where are papillomavirus trophic for?

Answer 34

Squamous epithelium, as depend on terminal squamous epithelial cell differentiation to replicate.

Question 35

Are papillomavirus benign or malignant?

Answer 35

Benign usually

Question 36

What is the structure of papillomaviruses?

Answer 36

No envelope so stable

Question 37

What is genome of papillomaviruses like?

Answer 37

ds circular DNA, with early replication and late parts

Question 38

Which are the oncogenic gene products in papillomaviruses?

Answer 38

Early e.g. E5,6,7

Question 39

Which cell must be exposed for a papillomavirus to enter?

Answer 39

Basal stem cell

Question 40

What does early gene expression in papillomavirus push replication of?

Answer 40

Basal stem cells

Question 41

How does late gene expression begin in papillomaviruses?

Answer 41

Switch of cells into mature keratinocytes switches replication from plasmid to vegetational replication and late gene expression begins

Question 42

How does E6 interfere with cell cycle control?

Answer 42

Interacts with p53 and causes its degradation

Question 43

How does E7 interfere with cell cycle control?

Answer 43

Interacts with pRB and causes E2F-1 to always be released so the cell cycle continues

Question 44

What is the cofactor in CRPV skin carcinoma?

Answer 44

Methylcholanthrene

Question 45

Which type of herpesviruses are the oncogenic ones?

Answer 45

Gamma

Question 46

How do herpesviruses often become oncogenic?

Answer 46

Species jump

Question 47

What are two methods of activation of cellular oncogenes?

Answer 47

Cis or trans