Structure, chromosomal localization, and expression of 12 genes of the MAGE family

We reported previously that human gene MAGE-1 directs the expression of a tumor antigen recognized on a melanoma by autologous cytolytic T lymphocytes. Probing cosmid libraries with a MAGE-1 sequence, we identified 11 closely related genes. The analysis of hamster-human somatic cell hybrids indicated that the 12 MAGE genes are located in the q terminal region of chromosome X. Like MAGE-1, the 11 additional MAGE genes have their entire coding sequence located in the last exon, which shows 64%-85% identity with that of MAGE-1. The coding sequences of the MAGE genes predict the same main structural features for all MAGE proteins. In contrast, the promoters and first exons of the 12 MAGE genes show considerable variability, suggesting that the existence of this gene family enables the same function to be expressed under different transcriptional controls. The expression of each MAGE gene was evaluated by reverse transcription and polymerase chain reaction amplification. Six genes of the MAGE family including MAGE-1 were found to be expressed at a high level in a number of tumors of various histological types. None was expressed in a large panel of healthy tissues, with the exception of testis and placenta.