Human N-acetylglucosaminyltransferaser III gene is transcribed from multiple promoters

We have isolated cDNA clones for the human N- acetylglucosaminyltransferase III (GlcNAc-transferase III) gene. Two of them, H15 and H20, contain 5' non-coding regions that are totally different from each other except for 8 bp adjacent to the putative initiation codon. Analysis of one of the genomic cosmid clones containing the GlcNAc- transferase III coding region. Hug3, revealed that the 5' non-coding regions of H15 and H20 contain two and one exons, respectively, in addition to the exon containing the sites were determined by primer-extension analysis and 5'-rapid amplification of cDNA ends (RACE). Both H15-specific and H20- specific primers gave cDNAs longer than those expected from the lengths of dH15 and H20, and a primer complementary to the region around the intron/exon junction near the putative initiation codon also gave distinct signals. Promoter activities of the 5'-flanking regions of H15, H20 and exon 1 were measured in a human hepatoblastoma cell line. HuH-6 cells by luciferase assays. The 5'-flanking region of exon 1 was the most active, whilst that of H15 was several times less active, and that of H20 was inactive. Our study suggests that multiple promoters of the GlcNAc-transferase III gene contribute to the complex regulation of this gene.