Type IA DNA topoisomerases: Strictly one step at a time

摘要

During DNA replication and transcription, the winding of the DNA helix undergoes dramatic changes that give rise to DNA supercoiling. Additionally, both DNA replication and recombination can leave the DNA in a tangled, catenated, or interwound state. DNA topoisomerases are the enzymes charged with resolving these topological problems in the DNA (for reviews, see refs. 1-3). In addition, in bacteria two or more DNA topoisomerases act in concert to maintain a fixed global level of helical tension in the DNA that is critical for its proper function.