DIVERGENT STRUCTURE OF THE HUMAN SYNEXIN (ANNEXIN-VII) GENE AND ASSIGNMENT TO CHROMOSOME-10

The human synexin (annexin VII) gene occurs as a single copy at chromo some 10q21.1-21.2 and substantially deviates in size and in the locati on of splice junctions from the other two well-characterized members o f the annexin gene family, lipocortin I (annexin I) and calpactin I (a nnexin II). The synexin gene contains 14 exons, including an alternati vely spliced cassette exon, and spans approximately 34 kb of DNA. Only five of the fourteen splice junctions are conserved compared to other annexins, and the differences are particularly pronounced in the exon s that encode the C-terminal third and fourth conserved repeats in the gene product. Although parallels between exons and protein domains we re not apparent, we did observe clustering of splice junctions corresp onding to either the unique N-terminal domain or the conserved C-termi nal tetrad repeat domain, which is common to all annexins. Furthermore , a complete analysis of the 5' flanking region of the annexin VII gen e revealed an entirely different set of cis-acting and enhancer elemen ts compared to other annexin genes. We conclude that the annexin VII g ene may have arisen by a divergence from the evolutionary pathway take n by both annexins I and II.