PCR-Based Cloning of DNA Topoisomerase Genes

Numerous type I and type II DNA topoisomerase genes have now been identified and sequenced from both the eukaryotic and prokaryotic sources. Amino acid sequence alignments of these genes firmly establish that all type II topoisomerase genes belong to one family regardless of source, whereas among the type I topoisomerase genes, there are two subtypes: one typified by the bacterial top A gene and the other by the eukaryotic TOP1 gene (1 ,2 ). The high degree of sequence conservation among these families of genes provides a straightforward approach to identifying new genes by PCR methodologies. These genes may be used as specific DNA probes for genomic organization studies, for topoisomerase-targeting drug resistance studies, or they may be overexpressed as recombinant proteins for structure-function and comparative analyses.