Chapter 13: some questions about viruses

Question 1

Human papillomavirus.

• What type of infectious agent?
• What type(s) of cancer does it cause?
• What is/are the major effectors of the infectious agent?

Answer 1

• DNA virus
• Cervical, throat, anogenital
• E6 and E7

Question 2

Epistein-Barr virus (EBV).

• What type of infectious agent?
• What type(s) of cancer does it cause?
• What is/are the major effectors of the infectious agent?

Answer 2

• DNA virus
• Nasopharyngeal, some lymphomas
• LMP1

Question 3

Kaposi’s sarcoma-associated herpesvirus.

• What type of infectious agent?
• What type(s) of cancer does it cause?
• What is/are the major effectors of the infectious agent?

Answer 3

• DNA virus
• Kaposi’s sarcoma
• LANA

Question 4

Human T-cell leukemia virus.

• What type of infectious agent?
• What type(s) of cancer does it cause?
• What is/are the major effectors of the infectious agent?

Answer 4

• RNA virus
• T cell leukemia
• TAX protein

Question 5

Hepatitis B (and C) virus.

• What type of infectious agent?
• What type(s) of cancer does it cause?
• What is/are the major effectors of the infectious agent?

Answer 5

• DNA virus
• Liver
• HBV X

Question 6

Helicobacter pylori.

• What type of infectious agent?
• What type(s) of cancer does it cause?
• What is/are the major effectors of the infectious agent?

Answer 6

• Bacterium
• Gastric
• Cag A

Question 7

Epistein-Barr virus (EBV). Why is LMP1 its major effector?

Answer 7

It acts as an oncoprotein and can activate genes important for cell proliferation (e.g. EGFR) and inhibition of apoptosis. It also activates NF-kB.

Question 8

Human papillomavirus (HPV). Why are E6 and E7 its major effectors?

Answer 8

E7 binds and triggers degradation of Rb, thus preventing sequestration of E2F (which leads to the expression of E2F-responsive genes like cyclin A and E). E6 binds and triggers p53 degradation.

Question 9

Human T-cell lymphotrophic virus type 1 (HTLV-1). Why is the TAX protein its major effector?

Answer 9

TAX exerts its functions by protein-protein interaction with over a hundred cellular proteins generarting a plethora of effects, including stimulation of cell growth, inhibition of DNA repair and alteration of the cell cycle by activating CDKs. It can also activate NF-kB and AP1 and can interfere with several tumor suppressor proteins.

Question 10

Hepatitis B virus (HBV). Why is HBV X its major effector?

Answer 10

HBV X activates proto-oncogenes, interacts with NF-kB and binds and inactivates p53. It can also bind to proteins involved in epigenetic and transcriptional regulation such as chromatin-modifying enzymes and transcription factors.

Question 11

Kaposi’s sarcoma-associated herpesvirus. Why is LANA its major effector?

Answer 11

LANA interferes with the function of Rb and p53.

Question 12

Helicobacter pylori. Why is Cag A its major effector?

Answer 12

Cag A stands for cytotoxin-associated antigen A. Cag A is injected into cells by the bacterial secretion system to elicit cellular effects such as stimulation of cell growth. Cag A is phosphorylated by Src and Abl family of tyrosine kinases. Phophorylated Cag A interacts with SH2 domain-containing proteins such as SHP-2 and Grb2.