HUMAN N-ACETYLGLUCOSAMINYLTRANSFERASE-III GENE IS TRANSCRIBED FROM MULTIPLE PROMOTERS

We have isolated cDNA clones for the human N-acetylglucosaminyltransfe rase III (GlcNAc-transferase III) gene. Two of them, H15 and H20, cont ain 5' non-coding regions that are totally different from each other e xcept 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 a nd H20 contain two and one exons, respectively, in addition to the exo n containing the coding region (exon 1). These have arisen as the resu lt of alternative splicing. The transcription-initiation sites were de termined by primer-extension analysis and 5'-rapid amplification of cD NA ends (RACE), Both H15-specific and H20-specific primers gave cDNAs longer than those expected from the lengths of H15 and H20, and a prim er complementary to the region around the intron/exon junction near th e putative initiation codon also gave distinct signals. Promoter activ ities 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 s tudy suggests that multiple promoters of the GlcNAc-transferase III ge ne contribute to the complex regulation of this gene.