Evolutionary Analyses of DNA Topoisomerases II and IA

DNA strand scission and topology changes are catalyzed by DNA topoisomerases. Previous studies suggest that Type IIB topoisomerase evolved from Type IIA by gene duplication, recombination and absence. However, this study shows that the evolutionary relationship between Type IA and IIB is closer than that between Type IIA and IIB. Thus, Type IIB is possibly from Type IA, or Type IIB is a special form of IA in archaebacteria; Type IIB is probably evolved from IIA via IA rather than from IIA directly. During the evolution of IIA to IIB via IA, the catalytic mechanisms of DNA topoisomerases have also been changed; that is, metal ions are necessary in the catalyses for both IA and IIA, but no ion is needed for IIB.

Keywords
DNA topoisomerase; CAP-like domain; Toprim domain; Molecular evolution; Catalytic mechanism