p73 and p63 protein stability: the way to regulate function?

While the p53 homologue p73 has been found to be involved in tumorigenesis, the molecular mechanisms involved in this function are still not fully evident. The presence of two distinct promoters allows the formation of two proteins with opposite effects: while TA-p73 shows pro-apoptotic effects, DeltaN-p73 has an evident anti-apoptotic function. The relative expression of the two proteins is in fact related to the prognosis of several cancers. Since both p73 and p63, the other member of the same family, share the ability to interact with each other, it is important to understand the mechanisms that control the degradation and stability of both proteins, and their relative isoforms. p73 and p63 stability is regulated not only by protein modifications (phosphorylation, acetylation) but also by its degradation in the proteasome. To this end, the interaction with Mdm2, p300/CBP, and SUMO-1 are discussed in details.