THE HUMAN HOMOGENTISATE 1,2-DIOXYGENASE (HGO) GENE

Alkaptonuria (AKU;McKusick No, 203500), a rare hereditary disorder of the phenylalanine catabolism, was the first disease to be interpreted as an inborn error of metabolism (A. E. Garrod, 1902, Lancet 2: 1616-1 620). AKU patients are deficient for homogentisate 1,2-dioxygenase (HG O; EC 1.13.11.5). This enzymatic deficiency causes homogentisic acidur ia, ochronosis, and arthritis. Recently we cloned the human HGO gene a nd showed that AKU patients carry two copies of a loss-of-function HGO allele. Here we describe the complete nucleotide sequence of the huma n HGO gene and the identification of its promoter region. The human HG O gene spans 54,363 bp and codes for a 1715-nt-long transcript that is split into 14 exons ranging from 35 to 360 bp, The HGO introns, 605 t o 17,687 bp in length, contain representatives of the major classes of repetitive elements, including several simple sequence repeats (SSR). Two of these SSRs, a (CT)(n) repeat in intron 4 and a (CA)(n) repeat in intron 13, were found to be polymorphic in a Spanish population sam ple. The HGO transcription start site was determined by primer extensi on. We report that sequences from -1074 to +89 bp (relative to the HGO transcription start site) are sufficient to promote transcription of a CAT reporter gene in human liver cells and that this fragment contai ns putative binding sites for liver-enriched transcription factors tha t might be involved in the regulation of HGO expression in liver. (C) 1997 Academic Press.