Topoisomerase II

**Semantic type:** Amino Acid, Peptide, or Protein|Enzyme

**Definition:** Topoisomerase II catalyzes relaxation of supercoiled DNA molecules, catenation, decatenation, knotting, and unknotting of circular DNA. The topoisomerase II reaction appears to involve crossing-over of two DNA segments. Human cells contain two topoisomerase II isozymes: alpha and beta from distinct genes. DNA topoisomerase II alpha is associated with the Pol II holoenzyme and is required for chromatin-dependent co-activation. Transcription results in superhelical tension; topoisomerase II relaxation activity is essential for productive RNA synthesis on nucleosomal DNA. (from OMIM 126430 and NCI)

**Synonyms:** - DNA Topoisomerase II - TOP2 - Topo II - Topoisomerase 2