Abstract
The tumor suppressor genes or antioncogene, is a gene that controls the cell cycle and regulates the proliferation capacity. Their protein product inhibits mitosis. By contrast, the maturation or the loss of the function of an antioncogene promotes the appearance and proliferation of tumors or cancer. An example of tumor suppressor gene (TSG) is p53. The product of the gene p53 is a protein of 53 kilodaltons (hence the name). p53, known also as TP53 (tumor protein) is a transcription factor discovered in 1979 and mapped to the short arm oh the chromosome 17 (NCBI 2007). Existing at a very low concentration in non-stressed cells, the p53 protein prevents a cell from completing the cell cycle. Under stress conditions, the p53 protein accumulates in the cell, binds in its tetrameric form to p53-response elements and induces the transcription of various genes that are involved in cell-cycle control, apoptosis, DNA repair, differentiation and senescence. The loss of p53 tumor suppressor gene activity by mutation or deletion of TP53 or inhibition of p53 allows the proliferation of the cells that are damaged under stress conditions. This uncontrolled proliferation can lead to tumor development. As such, p53 is described as "the guardian of the genome". Its activity and role in the cell is summarized in figure 1 (Chène P 2003).
