Molecular cloning and genomic analysis of mouse glucuronyltransferase involved in biosynthesis of the HNK-1 epitope

cDNA and genomic clones encoding the mouse glucuronyltransferase (GlcAT-P) involved in biosynthesis of the HNK-1 carbohydrate epitope were isolated and the structural organization of the gene was determined. The predicted amino acid sequence of mouse GlcAT-P is 96.2 and 98.2% identical to those of the rat and human enzymes, respectively. Alternatively spliced isoforms of mouse GlcAT-P are present in the brain and encode two proteins that are identical throughout their length except for an additional 13 amino acids in the N-terminal cytoplasmic domain of the major form. The coding region of GlcAT-P is composed of 5 exons spanning approximately 6 kb, and the GlcAT-P gene was mapped to the A4 region of mouse chromosome 9. Upstream of the transcriptional start site, no typical TATA or CCAAT box was found, but binding sites for several known transcription factors including Sp1 and Krox-20 were identified. Transient transfection of luciferase reporter constructs demonstrated that a 207 bp fragment of the 5'-upstream region acts as a strong promoter in PC-12 cells, which express the HNK-1 epitope, but not in COS-1 cells. Thus, this minimal promoter region of GlcAT-P is suggested to be associated with the regulation of HNK-1 expression.