TP53 and cancer: In cancer cells, the transcriptional activity of TAp73 is kept in check by several protein inhibitors, such as ΔNp73, ΔNp63, iASPP38 and aurora kinase A,39 and mutant p53 form heterocomplexes with TAp73 and abrogate its transcriptional activity.33,34,38, 39, 40 MDM2, E3 ubiquitin ligase that binds p53 and promotes its ubiquitin-dependent degradation, blocks TAp73 transcriptional activity via direct binding to its transactivation domain but does not promote TAp73 proteolytic disassembly.