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The UDP-GlcNAc:dolichol-P GlcNAc-1-P transferase catalyzes the first and committed step in the dolichol cycle, thus playing a fundamental role in the pathway for protein N -glycosylation. The structure of the GlcNAc-1-P transferase gene has been previously elucidated in mouse and hamster. Moreover, the human cDNA has been cloned. Using sequence database tools, we deduced the genomic structure of the human GlcNAc-1-P transferase gene, which was experimentally confirmed by sequence analysis. The gene is composed of 9 exons and spans 5.5 kb. All splice acceptor and donor sites conform to the canonical AG/GT rule. The 5′-end of the gene is different from previously reported, as, consequently, the N-terminal of the encoded protein, which is predicted to be 408 amino acids long. The transcription start site, determined by 5′ RACE, occurs 180 nucleotides upstream of the translation initiation codon. Several potential transcription regulatory motifs, such as Sp-1, E4TF1 and ATF binding sites, were identified in the 5′-flanking region. A polyadenylation signal is located 466 bp downstream of the stop codon. The genomic organization of the gene is similar to that of the corresponding mouse and hamster genes, though extensive homology is restricted to the coding regions. Analysis of a panel of radiation hybrids led to the assignment of the GlcNAc-1-P transferase gene to chromosome 11, at 4.19 cR from NIB361, according to the location of the homologous sequences in the database at 11q23. [ABSTRACT FROM AUTHOR]