Structure and function of an archaeal topoisomerase VI subunit with homology to the meiotic recombination factor Spo11

In all organisms, type II DNA topoisomerases are essential for untangling c hromosomal DNA. We have determined the structure of the DNA-binding core of the Methanococcus jannaschii DNA topoisomerase VI A subunit at 2.0 Angstro m resolution, The overall structure of this subunit is unique, demonstratin g that archaeal type II enzymes are distinct from other type II topoisomera ses, However, the core structure contains a pair of domains that are also f ound in type IA and classic type II topoisomerases, Together, these regions may form the basis of a DNA cleavage mechanism shared among these enzymes. The core A subunit is a dimer that contains a deep groove that spans both protomers, The dimer architecture suggests that DNA is bound in the groove, across the A subunit interface, and that the two monomers separate during DNA transport. The A subunit of topoisomerase VI is homologous to the meiot ic recombination factor, Spell, and this structure can serve as a template for probing Spell function in eukaryotes.