The tumor suppressor protein p53 is a transcription factor that is frequently mutated in human cancers. In response to DNA damage, unmutated or wild-type (wt) p53 protein is stabilized and activated by post-transcriptional modifications that enable it to induce either apoptosis or cell cycle arrest. Using a yeast p53-dissociator assay, we identified MAGED2 as a potential negative regulator of wt p53 activity. Subsequently, using co-immunoprecipitation and reporter gene assays in human cultured cells that are often adopted for functional analysis of p53 we demonstrated that MAGED2 interacted physically with p53 and modified its activity. Finally, we were able to illustrate expression of both p53 and MAGED2 within the same subcellular compartment, i.e. either nucleus or cytoplasm, in 2,682 human cancer tissue specimens using a common cancer tissue microarray and antibodies against MAGED2 and p53. The present results implicate MAGED2, a novel protein, as a p53-dissociator.