CELL-SPECIFIC EFFECTS OF P53 CDNA GOVERNED BY HOMOLOGOUS PROMOTER

The p53 gene participates in the cell proliferation arrest in response to DNA damage. The gene is malfunctioning in the majority of human tu mors. At the same time, the sensitivity of tumor cells to the expressi on of artificially introduced wild-type p53 is increased. However, in previous investigations the p53-mediated suppression of cell prolifera tion was studied on the background of the protein overexpression due t o the use of constructs containing a strong heterologous promoter. We attempted to create a model mimicking the physiological conditions of p53 expression. For this purpose, we placed the wild-type p53 and its His273 mutant under the control of the p53 promoter and Introduced bot h constructs into the retroviral suicide vector. The resulting recombi nant viruses were transfected into the LIM1215, SW480, A431, 293, HeLa , and K562 cell lines. All cell lines appeared to be extremely sensiti ve even to low expression of the wild-type p53. Only the LIM1215 line, which retained normal p53 expression on its own, yielded a small amou nt of colonies expressing the exogenous p53. HeLa cells could prolifer ate shortly, but further stopped to divide and underwent apoptosis as Judged by the electron microscopy. The His273 mutant expression was to lerated by most of the cell lines; however, the doubling time of the H eLa cells was somewhat increased along with a decrease in the confluen t cell culture density. These cells exhibited a greater dependence on the presence of fetal serum and conditioned medium factors. Expression of the p53/His273 in SW480 and A431 cell lines caused no change in th e above parameters.