Genomic structure and promoter analysis of the human  1,6-fucosyltransferase gene (FUT8)

GDP-l-Fuc:N-acetyl-[beta]-d-glucosaminide [alpha]1,6-fucosyltransferase ([alpha]1,6FucT) catalyzes the transfer of a fucosyl moiety from GDP-fucose to the asparagine-linked GlcNAc residue of complex N-glycans via [alpha]1,6-linkage. We have cloned the genomic DNA which encodes the human [alpha]1,6FucT gene (FUT8) and analyzed its structure. It was found that the gene consists of at least nine exons spanning more than a 50 kbp genomic region, and the coding sequence is divided into eight exons. The translation initiation codon was located at exon 2, and thus exon 1 encodes only 5'-untranslated sequences. Transcription initiation site of FUT8 was determined by 5'-rapid amplification of the cDNA end and a primer-extension analysis using the total RNA isolated from SK-OV-3 cells, which have a high level of [alpha]1,6FucT activity. We then characterized the FUT8 promoter region by a reporter gene assay. The luciferase reporter assay indicated that the 5'-flanking region of exon 1, which covered about 1 kbp, conferred the promoter activity in SK-OV-3 cells. This region contains potential binding sites for some transcription factors, such as bHLH, cMyb, GATA-1, as well as a TATA-box, but not a CCAAT motif. 5'-Untranslated sequences found in ESTs and the cDNA for the FUT8 suggest the presence of an additional exon(s) at the upstream of the first exon identified in this study, and therefore, the transcription of the gene would be regulated by multiple promoters.