The p53 tumour suppressor PMID:2046748,PMID:2142001,PMID:2142762,PMID:2137806,PMID:1639769 is a protein found in increased amounts in a wide variety of transformed cells. It is also detectable in many proliferating non-transformed cells, but it is undetectable or present at low levels in resting cells. It is frequently mutated or inactivated in many types of cancer. p53 seems to act as a tumour suppressor in some, but probably not all, tumour types. p53 has been implicated in cell cycle regulation, particularly in the monitoring of genomic DNA integrity prior to replication; for this reason it has been dubbed `guardian of the genome'.

p53 is a sequence-specific DNA-binding protein and transcription factor. The structure of p53 comprises 4 domains: an N-terminal transactivation domain; a central DNA-binding domain; an oligomerisation domain; and a C-terminal, basic, regulatory domain PMID:7796267,PMID:8023159. The structure of the oligomerisation domain consists of a dimer of dimers, each dimer consisting of 2 anti-parallel alpha-helices and an anti-parallel beta-sheet. The sheets lie on opposite sides of the tetramer and the helices form an unusual 4-helix bundle PMID:7796267,PMID:8023159. While the majority of p53 mutations found in human cancers are located in the DNA-binding domain, some are also found in the oligomerisation domain.

This superfamily entry represents the C-terminal domain of transcription factor p53 characterised in Drosophila. While the rest of the protein, in particular the DNA binding domain (DBD), is quite conserved between the different transcription factors such as p53 and p73, the C-terminal domain is highly divergent. The Drosophila p53 structure is characterised by an additional N-terminal beta-strand and a C-terminal helix PMID:17581633.

INTERPRO:IPR024631,PFAM:PF11619,DOI:10.1038/sj.emboj.7601764