Molecular genetic analysis of topoisomerase II gene from Drosophila melanogaster.

The gene encoding the Drosophila type II DNA topoisomerase has been isolated and characterized. The enzyme is coded for by a messenger RNA of about 5000 nucleotides, the expected size for the enzyme with MWr 170,000, and the gene is interrupted by four introns. The cytogenetic location of this gene has been mapped to the left arm of chromosome 2 at 37D2-6 by both in situ hybridization to polytene chromosomes and genomic blot-hybridization. The complete nucleotide sequence of the coding region and the flanking sequence has been determined. The deduced amino acid sequence shows interesting homology with topoisomerases II from bacteria, bacteriophage T4, and yeasts. The sequence homology between the Drosophila enzyme and those from Saccharomyces and Schizosaccharomyces is very extensive. This, in combination with the similar biochemical properties among all the eucaryotic DNA topoisomerases II, indicates that these enzymes are conserved during the course of evolution.