Viruses and Oncogenes Flashcards
cancer
arise from sequential mutations that create (activate) oncogenes and inactivate tumour-suppressor genes
How can viruses cause cancer?
can cause cancer, acting as oncogenes or as inactivators of tumour-suppressor genes
Proto-oncogene
A normal gene which, when altered by mutation, becomes an oncogene that can contribute to cancer
oncogene
- positively regulate cell growth
- proliferation
- dominant (even if they are mutated they can still be active)
- gain-of-function mutations
tumour-suppressor
- inhibit cell growth and proliferation
- inactivation leads to tumour development
- recessive or dominant-negative(even if one allele is mutated the other one can make up for it and take over the gene function)
- lose-of-function mutations
RNA viruses
- when they attack they try to promote growth using oncogenes
- by origin some oncogenes are from RNA viruses
- oncogenes include src, ras, c-myc, erbB, bfr-abl, c-raf
DNA viruses
- when they attack, they try to inhibit or insert themselves into a tumour suppressor
- by origin some tumour suppressors are from DNA viruses
- tumour suppressor include p53, p16, Rb, APC
Rous sarcoma virus
- causes tumors in chickens
- contains gene v-src coding a constitutively active cytoplasmic nonrecptor tyrosine kinase (pp60^src)
v-src
- oncogene
- is shorter than c-src (12 codons), and lacks Tyr527
c-src
- is an promo-oncogene
- are tyrosine kinases, inactivated by phosphorylation at Tyrians537
Some RNA viruses
- Rat sarcoma (ras): GTPase
- Erythroblastosis (erbA): thyroid hormone receptor
- Feline osteosarcoma (fos): transcription factor
- Simian sarcoma (sis): PDGF
long terminal repeat
are essential for the virus to infect the host cell and divide using the host replication machinery
