| Abstract: | The kinetics of repair of the ionizing radiation-induced DNA single- and double-strand breaks in the normal NIH 3T3 mouse cells and in those transformed with virus oncogenes v-myc has been investigated. The incubation of non-transformed cells for 18 hours in serum-free medium results in significant decrease in the rate of the single-strand DNA breaks repair during the first minutes of post-irradiation incubation. This effect is absent in transformed cells. The DNA double-strand breaks repair is more efficient in transformed NIH 3T3 cells as compared to that in the non-transformed ones both after their incubation in the medium with 10% fetal bovine serum or without serum. However, more significant differences in the rate of elimination of these DNA lesions was found in the serum-free medium. Hence, the presence of v-myc sequences in the transformed cells prevented from a decrease in the efficiency of DNA repair due to incubation of cell culture in serum-free medium. These results agree with the assumption that c-myc gene product may be a mediator in regulation of DNA repair by the epidermal growth factor. These data also show that the c-myc gene expression in an important condition providing a high efficiency of the constitutive DNA repair process. |
