CHARACTERIZATION OF THE NSE4/EID BINDING TO NSE3/MAGE PROTEINS

The SMC5/6 (Structure and Maintenance of Chromosome) complex is involved in DNA repair processes. It contains a sub-complex formed by 3 Non-smc-elements, Nse1-Nse3-Nse4. Nse3 is the yeast ortholog of the human MAGEG1, founding member of the mammalian MAGE protein superfamily. Nse4 is related to the mammalian EID (E1A-like Inhibitor of Differentiation) protein family. Our previous study has shown that the Nse3-Nse4 interaction is evolutionary conserved between mammalian MAGE and EID proteins. Here, using protein-protein interaction techniques (like PEPSCAN and yeast two-hybrid) and molecular modeling, we have identified the region in Nse4 responsible for the binding to Nse3. This region contains a conserved hydrophobic motif which mediates binding between human NSE4b and MAGEG1. In addition we have tested fragments of the other EID family members, homologous to the Nse4 hydrophobic motif, and observed that they bind to most MAGE proteins, suggesting that this domain is conserved within all EID members. However, the binding affinity of the EID hydrophobic motif differs between different MAGE proteins. These results bring new insights into MAGE-EID binding and evolution.