The p53 tumor suppressor is a 53 kDa nuclear phosphoprotein of 393 amino acids that is encoded by the TP53 gene (20 kb with 11 exons and 10 introns) and characterized by the presence of several structural and functional domains, including a N-terminus, a central core domain, a C-terminal region, a strongly basic carboxyl-terminal regulatory domain, a nuclear localization signal sequence and three nuclear export signal sequence. The p53 is considered as a major “guardian of genome” for its activities in a wide range of cellular events, including cell-cycle regulation, induction of apoptosis, gene amplification, DNA recombination, chromosomal segregation and cellular senescence.