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 chromosomal DNA. We have determined the structure of the DNA-binding core of the Methanococcus jannaschii DNA topoisomerase VI A subunit at 2.0 Angstrom resolution, The overall structure of this subunit is unique, demonstrating that archaeal type II enzymes are distinct from other type II topoisomerases, However, the core structure contains a pair of domains that are also found 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 meiotic recombination factor, Spell, and this structure can serve as a template for probing Spell function in eukaryotes.