STRUCTURE OF THE HUMAN HEXOKINASE TYPE-I GENE AND NUCLEOTIDE-SEQUENCEOF THE 5'-FLANKING REGION

This study reports the precise intron/exon boundaries and intron/exon composition of the human hexokinase type I gene. A yeast artificial ch romosome containing the hexokinase type I gene was isolated from the y east artificial chromosome library of the Centre d'Etude du Polymorphi sme Humaine. A cosmid sublibrary was created and direct sequencing of the individual cosmids was used to provide the exon/intron organizatio n. The human hexokinase type I gene was found to be composed of 18 exo ns ranging in size from 63 to 305 bp. Intron 1 is at least 15 kb in le ngth, whereas intron 2 spans at least 10 kb. Overall, the length of th e 17 introns ranges from 104 to greater than 15 kb. The entire coding region is contained in at least 75 kb of the gene. The structure of th e gene reveals a remarkable conservation of the size of the exons comp ared with glucokinase and hexokinase type II. Isolation of the 5' flan king region of the gene revealed a 75-90 % identity with the rat seque nce. Direct evidence of an alternative red-blood-cell-specific exon 1 located upstream of the 5' flanking region of the gene is also provide d.