IDENTIFICATION AND INTRACELLULAR LOCATION OF MAGE-3 GENE-PRODUCT

The human MAGE-3 gene encodes a melanoma antigenic epitope recognized by specific cytotoxic T lymphocytes, but its gene product has not been identified thus far, We produced a recombinant MAGE-3 gene product by expression cloning of the entire reading frame in the context of a fu sion protein characterized by a 10-histidine tall, allowing purificati on by metal chelation on a nickel Sepharose column, The semipurified p roduct was used to generate MAGE-3-specific monoclonal antibodies. One reagent could identify by immunoblotting the native MAGE-3 gene produ ct as a M(r) 48,000 protein in lysates of cell lines showing evidence of MAGE-3 gene expression. No apparent cross-reactivity with recombina nt or native MAGE-1 gene product was observed, Immunohistochemistry sh ows that, closely resembling the MAGE-1 gene product, MAGE-3 is a cyto plasmic protein.