GENOMIC ORGANIZATION OF THE 3'-REGION OF THE HUMAN MUC5AC MUCIN GENE - ADDITIONAL EVIDENCE FOR A COMMON ANCESTRAL GENE FOR THE 11P15.5 MUCIN GENE FAMILY

The human mucin gene MU5SAC is mapped clustered with MUC2, MUC5B and M UC6 on chromosome 11p15.5. We report here the isolation and characteri zation of a genomic cosmid clone, designated ELO9, spanning the 3'-reg ion of MUC5AC and the 5'-region of MUC5B, allowing us to conclude that MUC5AC and MUC5B have the same transcriptional orientation, We determ ined the genomic organization and the entire sequence of the 3'-region of MUC5AC. The comparative molecular analysis of MUC5AC and MUC5B poi nts to a remarkable similarity in the size and the distribution of exo ns, and in the type of splice sites, supporting the notion that MUC5AC and MUC5B have evolved from a single common ancestral gene. The deriv ation of the four genes of the 11p15.5 mucin gene family from a single ancestral gene is discussed.