Structural organization of the human α-galactosidase A gene: Further evidence for the absence of a 3' untranslated region

Human α-galactosidase A (α-D-galactoside galactohydrolase; EC 3.2.1.22) is a lysosomal hydrolase encoded by a gene localized to the chromosomal region Xq22. The deficient activity of this enzyme results in Fabry disease, an X chromosome-linked recessive disorder that leads to premature death in affected males. For studies of the structure and function of α-galactosidase A and for characterization of the genetic lesions in families with Fabry disease, the full-length cDNA was isolated, sequenced, and used to screen human genomic libraries. The 1393-base-pair full-length cDNA had a 60-nucleotide 5' untranslated region and encoded a precursor peptide of 429 amino acids including a signal peptide of 31 residues. Three overlapping λ clones spanning 32 kilobases were identified that contained the entire ≃12-kilobase chromosomal gene as well as ≃9 and ≃11 kilobases of 5' and 3' flanking sequence, respectively. The gene had seven exons. The genomic exonic and full-length cDNA sequences were identical. All intron-exon splice junctions conformed to the GT/AT consensus sequence. The 5' flanking region of this lysosomal housekeeping gene contained Sp1 and CCAAT box promoter elements as well as sequences corresponding to the activator protein 1 (AP1), octanucleotide ('OCTA'), and 'core' enhancer elements. There was an upstream 'HTF' island (Hpa II tiny fragments) followed by four direct repeats of the 'chorion box' enhancer. The unique lack of a 3' untranslated sequence in the α-galactosidase A cDNA was confirmed by sequencing additional cDNA clones and the genomic 3' region.