The Georgiev promotor hypothesis about the cutting of cell genome and the latter being subjected to promotor control and virus regulation was used. On its basis the mechanism of temperature switching off of Src oncogene TS-mutant was investigated. It was shown that the model can correlate with the experiment in suggesting the regulating enzyme sigmoid kinetics and the temperature optimum below 35 degrees C. Hysteretic effect allows one to maintain a "healthy" state throughout the temperature switching off.