What makes RSV oncogenic?
These diagrams show the effect of temperature on cells infected with RSV that is normal in every respect except that its src gene carries a mutation making it temperature-sensitive. (Actually, it is not the gene that is sensitive to temperature, but its protein product.) • At 35°C the protein encoded by src is active and the host cells transformed. • At 41°C the protein is denatured and the cells grow normally; that is, show contact inhibition, etc. The process is reversible. The cells can be quickly and repeatedly switched from one state to the other simply by changing the temperature. So the correct expression of a single gene, src, is all that it needed to transform these cells. (Even though able to grow normally in the absence of the Rous src protein, these cells were surely not “normal”. Analysis of other tumors has repeatedly shown that it takes a number of mutations to convert truly-normal cells into transformed/cancerous ones.
