Structure of the Gene for Type I Hexokinase from Rat

Based on presumed analogy with the previously characterized gene encoding the Type II isozyme of rat hexokinase (Printz, R. L., Koch, S., Potter, L. R., OʹDougherty, R. M., Tiesinga, J. J., Moritz, S., and Granner, D. K.,J. Biol. Chem.268, 5209–5219, 1993), the locations of splice sites in the gene encoding the rat Type I isozyme of hexokinase have been determined by PCR amplification of intronic DNA. Sequences at the splice sites conform to the consensus sequence, with GT and AG being found at 5′ and 3′ ends of the introns, respectively. Sizes of exons 1 and 2 were determined directly while others were estimated based on identified splice sites and the previously determined cDNA sequence. These exon sizes were confirmed by PCR amplification, which gave products having sizes consistent with those of introns and exons predicted to be within the amplified sequence. Thus, it is unlikely that the gene encoding the Type I isozyme contains any introns not having analogs in the gene for Type II hexokinase. The deduced structure for the rat Type I hexokinase gene is therefore identical to that for the rat Type II isozyme, and spans over 51 kb. Six tandem repeat sequences of (AC/GT)nhave been identified in the 5′ flanking region and in introns 10, 11, 12, and 16; this is an unusually high frequency of tandem repeat sequences.