Final answer:
DNA topoisomerase is non-covalently attached to the TOPO site and performs ligation by temporarily untwisting the DNA helix to relieve supercoiling.
Step-by-step explanation:
DNA topoisomerase is non-covalently attached to the TOPO site and performs ligation. Topoisomerases are enzymes that relieve the pressure resulting from supercoiling by breaking and reforming DNA's nucleotide base pairs. They do this by temporarily untwisting the DNA helix.