Molecular cloning and structural characterization of the human histidase gene (HAL)
- Nagoya City Univ. Medical School (Japan)
Histidase (EC 4.3.1.3) is a cytosolic enzyme that catalyzes the nonoxidative determination of histidine to urocanic acid. Histidinemia, resulting from reduced histidase activity as reported in Cambridge stock his/her mice and in humans, is the most frequent inborn metabolic error in Japan. The histidase chromosomal gene (HAL) was isolated from a {lambda}EMBL-3 human genomic library using the human histidase cDNA as a probe. Restriction mapping and Southern blot analysis of the isolated clones reveal a single-copy gene spanning approximately 25 kb and consisting of 21 exons. Exon 1 encodes only 5{prime} untranslated sequence of liver histidase mRNA, with protein coding beginning in exon 2. A rarely observed 5{prime}GC, similar to that reported in the human P-450(SCC) gene, is present in intron 20. All other splicing junctions adhere to the canonical GT/AG rule. A TATA box sequence is located 25 bp upstream of the liver histidase transcription initiation site determined by S1 nuclease protection analysis. Several liver- and epidermis-specific transcription factor binding sites, including C/EBP, NFIL6, HNF5, AP2/ KER1, MNF, and others, are also identified in the 5{prime} flanking region. Consistent with the hepatic and epidermal expression of histidase, this finding suggests that histidase transcription may be regulated by these factors. We further identify a polymorphism (A to G transition) in the histidase coding region of exon 16. The human histidase genomic structure presented here should facilitate the molecular investigation of symptomatic and asymptomatic forms of histidinemia. 69 refs., 4 figs., 1 tab.
- OSTI ID:
- 433289
- Journal Information:
- Genomics, Vol. 29, Issue 1; Other Information: PBD: 1 Sep 1995
- Country of Publication:
- United States
- Language:
- English
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