p73 is a protein related to the p53 tumor protein. it has also been considered a tumor suppressor. It is involved in cell cycle regulation, and induction of apoptosis. Like p53, p73 is characterized by the presence of different isoforms of the protein. This is explained by splice variants, and an alternative promoter in the DNA sequence.TP73 protein was the first identified homologue of the tumor suppressor gene, p53. Like p53, p73 has several variants. It is expressed as distinct forms differing at either at the C- or the N-terminus. Currently, six different C-terminus splicing variants have been found in normal cells. The p73 gene encodes a protein with a significant sequence homology and a functional similarity with the tumor suppressor p53. The over-expression of p73 in cultured cells promotes a growth arrest and/or apoptosis similarly to p53.