Covalent modification of the oncogene product Mdm2 by the ubiquitin-related protein SUMO1 protects it from ubiquitination and enhances its E3 ligase activity towards p53 in vitro. Disappearance of ...

However, loss of p53 tumour-suppressor activity can also occur through amplification of MDM2. As MDM2 is a negative regulator of p53, this promotes p53 degradation and inhibits p53 tumour ...