ENIGMAS OF P53 TUMOR-SUPPRESSOR GENE

In the review the data about the structure and functions of p53 tumor suppressor gene and its product, a nuclear phosphoprotein p53, are pre sented. Gene p53 is often subjected to mutations during the progressio n of many human tumors, becoming highly malignant. p53 protein binds s equence-specifically to DNA of eucaryotic cells and functions as a fac tor of transcription, suppressing the activity of many oncogenes and g rowth factor genes, but activating genes of some differentiation facto rs. Mutant p53 protein, on the contrary, is unable to bind specificall y with DNA and expresses some features of oncogenes. The main function of p53 protein is the guarding of cellular genome integrity. DNA dama ge is catched by p53 as a signal for the induction of p21 synthesis, a n inhibitor of cyclin-dependent kinases and the proliferative nuclear antigen PCNA. The double block arrests the cell on a boundary of G(1)/ S phases (G(1) block). Block G(2) caused by the uncompleted DNA replic ation is also realized with the participation of p53. Both blocks enab le a cell to enter the mitosis with repaired and completely replicated DNA. Protein p53 plays also an essential role in the programmed cell death - apoptosis.