Melanoma antigen D2, a substrate of ATM, is a nucleolar protein that shuttles with cell cycle and cellular stress.

ATM coordinates numerous facets of the highly regulated DDR network. In order to identify new ATM substrates we have performed a yeast two hybrid experiment with HEAT domains of ATM and an HeLa cDNA library. Melanoma antigen D2 (MAGED2) was one of the interacting proteins identified in this screen. MAGED2 belongs to the type II Melanoma AntiGEn (MAGE) family. MAGE homology domain, shared by all MAGE proteins, was shown to enhance E3 ligase activity. Actually, little is known about MAGED2 functions. Like every type II MAGE protein, it is expressed in all adult tissues. However, MAGE-D2 has the particularity to be over-expressed in numerous primary cancer and metastasis and it is now recognized as a tumour marker. This over-expression suggests that MAGED2 could be important for the process of cancerisation. MAGED2 was also shown to be a negative regulator of p53, but we did not confirm this property. Proteomic analyses also detected numerous phosphorylated or acetylated residues in response to stress and during cell cycle progression, suggesting a role in cellular signal transduction. We identified the residues targeted by ATM in MAGE-D2 and analysed the localisation of MAGED2 during the interphase and after genotoxic/nucleolar stresses.