Viral Oncogenesis & Classification

Question 1

Explain the general mechanisms of viral oncogenes

Answer 1

• Carry oncogenes: SRC is a mutated overactive intracellular signal trasnducer (induce mitosis) (ex. chicken retrovirus - Rous Sarcoma Virus)
• Activate oncogenes: Retroviruses insert provirus into cellular chromosomes that may activate proto-oncogenes
• Inactivate tumor suppressor genes: retroviruses insert provirus into cellular chromosomes; may inactivate tumor suppressor genes or activate proto-oncogenes
• chronic injury-regeneration results in mutation accumulation: stimulates stem cells and neighboring cells to grow; repeated mitosis increases mutations
• Immunosuppression: Ex: HIV infects CD4+ T lymphocytes and kills them

Question 2

Define proto-oncogene

Answer 2

normal gene that promotes cell division or suppresses cell death and can become oncogenes when mutated or overexpressed

Question 3

Define proto-oncogene and give examples

Answer 3

normal gene that promotes cell division or suppresses cell death and can become oncogenes when mutated or overexpressed
-growth factors, growth factor receptors, signal transducers, transcription factors, cyclin-dependent kinases

Question 4

Define tumor suppressor gene

Answer 4

gene that suppresses cell division or promotes cell death

results in tumor when both alleles are mutated

Question 5

Explain the actions of the major tumorigenic mechanisms of HIV and target cells

Answer 5

infects and kills CD4+ T-lymphocytes
causes AIDS
compromises immunosurveillance –> promotes cancer
- Kaposi sarcoma, lymphoma, cervical cancer, other cancers

Question 6

Explain the actions of the major tumorigenic mechanisms of HTLV-I and target cells

Answer 6

infects and transforms CD4+ T-lymphocytes (uncontrolled endless proliferation)
uses tax to inactivate p53
transmitted by breastfeeding
high infection rates in Japanese culture
small percentage actually get cancer (2-5%)

Question 7

Explain the actions of the major tumorigenic mechanisms of EBV and taregt cells

Answer 7

• productive infection in epithelial cells of pharynx and salivary glands
• nonproductive in B lymphocytes but activates them
  
  • upregulates c-Myc which is involved in normal B cell activation, proliferation of B cells
• infect and immortalize B cells (in vitro)
• multifactorial

Question 8

Explain the actions of the major tumorigenic mechanisms of KSAV and target cells

Answer 8

• affects >50% Africans
• causes cancer in immunosuppressed
• AIDS defining in HIV positive patients
• encodes for cyclin D, cytokines, chemokine receptors to control cell proliferation

Question 9

Explain the actions of the major tumorigenic mechanisms of HPV and target cells

Answer 9

• dsDNA

- early genes (manipulate cell and replicate viral DNA) located upstream of late genes (encode capsid proteins)

Question 10

What is tax?

Answer 10

viral transcription factor that activates and represses cellular genes

- inactivate P53
- used in HTLV-I

Question 11

How is L1 capsid protein in HIV used to make a vaccine?

Answer 11

L1 capsid protein can spontaneously assemble into capsid structure

Question 12

Explain how viruses are classified into families based on the type of nucleic acid in the genome, number and polarity of nucleic acid strands, mode of replication and size, structure and symmetry of the virus particle

Answer 12

.