Cloning and sequencing of nineteen transcript isoforms of the human α2,3-sialyltransferase gene, ST3Gal III; its genomic organisation and expression in human tissues

Abstract

The recruitment of human peripheral blood leukocytes (PBL) to sites of infection and inflammation requires the surface expression of Sialyl Lewis x glycoconjugates (SLex) on white blood cells and their interaction with E- and P-selectins on activated endothelial cells. E-selectin has additionally been shown to interact with the sialyl Lewis a (SLea) epitope. Human ST3Gal III codes for an α2,3-sialyltransferase involved in the biosynthesis of both SLea and SLex epitopes, although the latter with a lower efficiency. We have cloned and sequenced human ST3Gal III gene transcripts from human peripheral blood leukocytes, covering the coding region of this gene. Within our clones we isolated 19 different transcripts with a wide variety of deletions from 45 to 896 nucleotides, and insertions of 26 to 173 nucleotides. Among the insertions we identified two new exons (E3, E6). In order to map and characterise the ST3Gal III gene we used the GenBank database and "computer-cloned" and characterised the genomic organisation of the ST3Gal III gene. The coding sequences of the ST3Gal IIIgene stretch over a gene sequence of approximately 223 Kb comprised of 15 exons. RT-PCR and laser-induced fluorescent capillary electrophoresis (LIF-CE) were used to examine the expression of this gene in twenty-one human tissues, which showed a highly specific tissue expression pattern. Neural and muscular tissues showed the most complex patterns and were distinctly different from all other tissues examined.