Question

Human papilloma virus (HPV) is the most common sexually transmitted infection, with 45% of 20-24 yr old women infected. Infection of the genitalia and cervix with HPV increases the risk of cervical cancer 10-fold. Two proteins encoded by HPV DNA bind to p53 and Rb. Which of the following do you think would Best describe the function of those two HPV proteins?

1. proto-oncogenes
2. oncogenes
3. tumor suppressor
4. gain of function mutant proteins

Answer 1

None of them. Of the options listed, three of them are mutations in the genome of the HOST organism, not the virus; and the proteins in question that bind to P53 and Rb, are not mutations, they are viral proteins binding to tumor suppressor genes (or proteins, it is not clear from the question). What I mean by this is that, according to the question, these two proteins most likely bind to either:

• P53 and Rb genes, preventing the transcription machinery from transcribing them. Therefore, there will be no tumor suppressor protein to fight cancer.
• P53 and Rb proteins, inhibiting or degrading them, eliminating their cancer-fighting activity.

But they do not cause a mutation in the host's genome. Furthermore, Proto-oncogenes, Oncogenes and Gain of funtion mutations are potential causes of cervical cancer, but, again, they are mutations in the genome of the organism that develops cancer, they are not directly related to the proteins that bind to P53 and Rb.

Even if these proteins would somehow mutate the P53 and Rb genes, they can not be considered Proto-oncogenes, Oncogenes or Gain of function mutations. The Oncogene would be the mutated P53 and Rb themselves.

Finally, they can not be Tumor suppressors because a tumor suppresor does the exact opposite of what HPV proteins do, it exists to prevent cancer, not to cause it.