ORGANIZATION OF THE HUMAN N-ACETYLGLUCOSAMINYLTRANSFERASE-V GENE

UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6-N-acetylglucosam inyltransferase V (GlcNAc transferase V), which catalyzes the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to alpha-6-D-mann oside, is an important enzyme regulating the branch formation in compl ex-type, N-linked oligosaccharides. It has been reported that the enzy mic activity of GlcNAc transferase V increases after viral transformat ion and the enzymic product is closely related to the metastasis of tu mors. We previously reported the purification, cDNA cloning and chromo somal mapping of human GlcNAc transferase V. In this study, we describ e the isolation of genomic clones encoding human GlcNAc transferase V and the structure of the gene. The human GlcNAc transferase V gene is divided into 17 exons, and the open reading frame is encoded by exons 2-17, spanning 155 kb. Analysis of the 5'-untranslated regions of mRNA s from various cells showed multiple sequences depending on the cell t ypes. The promoter region of the GlcNAc transferase V gene was charact erized by searching for any consensus sequences matching those for tra nscription-factor binding. The consensus sequences for a TATA box, AP- 1, AP-2, and some other transcription factors were found in the 5'-ups tream region of exon 1, and consensus sequences for LF-A1, HNF1-HP1, l iver-restricted transcription factors and other factors were also foun d in intron 1, Chloramphenicol acetyltransferase fusion plasmids with either the 5'-upstream region of exon 1 or intron 1 were constructed a nd transfected into COS-1 cells. Promoter activities of both DNA fragm ents were detected, indicating that transcription starts within this r egion. These data suggest that the human GlcNAc transferase V gene emp loys a multiple promoter system for its transcription, and gene expres sion may therefore be regulated in tissue-specific and cell-type-speci fic manners.