Structural organization of the human gamma-glutamyl hydrolase gene

gamma-Glutamyl hydrolase (GH) plays an important role in the metabolism of folic acid and the pharmacology of antifolates such as methotrexate. We hav e previously cloned and characterized the human GH cDNA. In this report, th e complete organization and structure of the human GH gene was determined. The human GH gene spans 24 kb in the human genome, with nine exons sized fr om 51 to 371 bp. All of exon-intron splice junctions follow the GT-AG rule. The sequence upstream of exon 1 consists of a promoter-like, GC-rich regio n and a number of putative cis active elements including Sp1, AP1, and MZF1 sites. A TATA sequence in the 5' region of human GH gene was not observed, similar to housekeeping genes known to be tissue-specific and differential ly expressed. S1 nuclease protection analysis with human liver, prostate, b rain, and mammary gland revealed a major transcription start point at nucle otide -125 relative to the ATG start codon and several minor transcription start points. Analysis of GH cDNA isolated from human liver indicated a nuc leotide change, T-->C, in the leader sequence of GH, which suggested a poly morphism. Studies of cDNA from different human tissue sources provided evid ence that there is a single spliced cDNA species in human. (C) 1999 Elsevie r Science B.V. All rights reserved.