P53 is a multifunctional protein with a molecular weight of 53 kDa that is activated in response to a variety of cellular stresses . It contributes to the cell cycle arrest in the G1 phase and to induce apoptosis is involved in the regulation of gene transcription in the process of cell differentiation and angiogenesis , and its best-known function, repair of DNA damage . Necessary in situations of cellular stress , which might jeopardize the integrity of the genome , known as the " guardian of the genome " .