Cell Growth, Cancer and Oncogenes
How Oncogenes Cause Cancer
Tumor Suppressor Genes
Cancer Genes in the Human Genome
Cell Cycle and Cancer WWW Links
We have already discussed the structure of the retroviruses in relation to
retrotransposons. It was mentioned that the oncogene of those viruses transform
a cell to unproliferated growth carry an oncogene in addition to the three
primary genes required of all retroviruses. The figure below is the generalized
structure of a retrovirus.
One of the best studied retroviruses infects chicken and is called Rous
Sarcoma Virus. The oncogene found in this retrovirus is
src. The product of this gene is a protein kinase that
phosphorylates tyrosine residues in other proteins. The protein products
of other retroviral oncogenes also regulate cell division processes and contain
one of four functions.
Copyright © 1998. Phillip McClean
Growth factor receptors - One example is epidermal growth factor receptor
which promotes wound healing by stimulating cell growth. Some factors function
as transmembrane protein kinases that are activated by an extracellular signal.
An example is v-erbB found in the Avian erythroblastosis virus
that infects chicken.
Protein kinases - These proteins alter the function of other proteins
by phosphorylating specific amino acid residues. The v-src from
the Rous Sarcoma virus which infects chickens is an example.
G-proteins - These proteins bind the nucleotide GTP, and also exhibit
GTPase activity. The v-H-ras oncogene of the Harvey murine
sarcoma virus which infects rats is an example.
Transcription factors - These proteins function by binding to DNA
and activating transcription. An example is the v-jun oncogene
of the Avian sarcoma virus that infects chickens.