DNA topoisomerase II (bacterial: DNA gyrase) (DNA gyrase (for bacteria); TOP2 (for eukaryotic topoisomerase II))

DNA topoisomerase II is an essential enzyme in both prokaryotes and eukaryotes that introduces transient double-strand breaks in DNA, using ATP hydrolysis, to modify DNA topology by removing or introducing supercoils, decatenating interlinked DNA molecules, and facilitating replication, transcription, and chromosome segregation[1][2][3][4][6][7][8]. DNA gyrase is a bacterial type II topoisomerase uniquely capable of introducing negative supercoils into DNA; it consists of two GyrA and two GyrB subunits and acts through a mechanism involving DNA cleavage, strand passage, and religation powered by ATP hydrolysis[3][6][1]. Both enzymes are exploited in anti-infective (particularly antibacterial) and anticancer therapy—bacterial gyrase is the target of fluoroquinolone antibiotics, while eukaryotic topoisomerase II is targeted by cancer chemotherapy agents such as etoposide[2][3][4]. Inhibition of these enzymes causes accumulation of DNA breaks, leading to cell death or viability loss, which underlies both their clinical utility and some safety challenges[2].

Other names

DNA gyraseTopoisomerase IIType II DNA topoisomeraseTOP2 (isoforms: Topoisomerase II alpha, Topoisomerase II beta)

Inhibition of DNA gyrase or topoisomerase II prevents relaxation or supercoiling of DNA, resulting in inhibition of DNA replication and transcription, leading to cell death. Poisoning mechanism (topoisomerase inhibitors): Drugs trap the enzyme-DNA cleavage complex, causing DNA double-strand breaks.