STRUCTURE OF THE HUMAN BIOTINIDASE GENE

Biotinidase cleaves biotin from biocytin, thereby recycling the vitami n. We have determined the structure of the human biotinidase gene. A g enomic clone, containing three exons that code for the mature enzyme, was obtained by screening a human genomic bacteriophage library with t he biotinidase cDNA by plaque hybridization. To obtain a clone contain ing the most 5' exon of the biotinidase cDNA, a human PAC library by P CR was screened. The human biotinidase gene is organized into four exo ns and spans at least 23 kb. The 5'-flanking region of exon 1 contains a CCAAT element, three initiator sequences, an octamer sequence, thre e methylation consensus sites, two GC boxes, and one HNF-5 site, but h as no TATA element. The region from nt -600 to +400 has features of a CpG island and resembles a housekeeping gene promoter. The structure a nd sequence of this gene are useful for identifying and characterizing mutations that cause biotinidase deficiency.