MARKER GENES FOR CYTOTOXIC EXPOSURE - P53

The growth suppressor p53 plays an important role in the regulation of cell proliferation, DNA repair and apoptosis. In wild-type p53 expres sing cells, gamma-irradiation induces an increase in the level of p53 protein and these cells exhibit a GI growth arrest. The p53-induced G( 1) growth arrest is abrogated in cells expressing mutant p53, or in ce lls where p53 is inactivated by complex formation with cellular or vir al proteins such as mdm2 or the E6 proteins of human papillomavirus (H PV) 16 or HPV18. Wild-type p53 expressing cells are radiosensitive whe reas mutant p53 expressing cells are radioresistant. In some cell type s, p53 mutations are observed after gamma-irradiation of cells althoug h this observation is not consistent for all cell types. Furthermore, it is not clear whether these mutations are the direct result of irrad iation or secondary effects.