Chromosomal location and structural organization of the human deoxycytidylate deaminase gene

Deoxycytidylate deaminase is an allosteric enzyme whose impairment can lead to deoxynucleotide imbalances that affect the fidelity of DNA synthesis. A DNA fragment encompassing the gene for deoxycytidylate deaminase has been isolated from a human lung fibroblast genomic library and sequenced in both directions through 26,764 base pairs. The previously isolated cDNA, which was used to establish the amino acid sequence for this enzyme (Weiner, K.X.B., Weiner, R.S., Maley, F., and Maley, G.F. (1993) J. Biol. Chem. 268, 12983-12989) was instrumental in isolating this gene. The gene consists of five exons of about 100 base pairs each, separated by four introns. The most striking feature of the genomic structure is that the second and third exons are separated by an intron of about 20 kilobases. The chromosomal location of the deaminase gene was determined by fluorescence in situ hybridization as 4q35, which is the extreme end of this chromosome. The position of this gene on chromosome 4, in addition to the role of its product in limiting potentially detrimental mutations, suggests that the normal operation of both the gene and its product is important to the well being of the organism.