What is the function of topoisomerase enzyme?

Type II topoisomerases change DNA topology by breaking and rejoining double-stranded DNA. These enzymes can introduce or remove supercoils and can separate two DNA duplexes that are intertwined (see Figure 12-16).

What is the role of topoisomerase in DNA replication?

Topoisomerases catalyze and guide the unknotting or unlinking of DNA by creating transient breaks in the DNA using a conserved tyrosine as the catalytic residue. The insertion of (viral) DNA into chromosomes and other forms of recombination can also require the action of topoisomerases.

What do topoisomerase II inhibitors do?

Topoisomerase II is an enzyme essential for DNA replication, chromosome condensation and chromosome segregation. Inhibitors of topoisomerase II are important drugs used in the therapy of many neoplasms including breast cancer, lung cancer, testicular cancer, lymphomas and sarcomas.

What does topoisomerase gyrase do?

DNA gyrase is an essential bacterial enzyme that catalyzes the ATP-dependent negative super-coiling of double-stranded closed-circular DNA. Gyrase belongs to a class of enzymes known as topoisomerases that are involved in the control of topological transitions of DNA.

What is topoisomerase in simple terms?

: any of a class of enzymes that reduce supercoiling in DNA by breaking and rejoining one or both strands of the DNA molecule.

What is the difference between topoisomerase and gyrase?

DNA gyrase and topoisomerase IV are the two type II topoisomerases present in bacteria. Gyrase is involved primarily in supporting nascent chain elongation during replication of the chromosome, whereas topoisomerase IV separates the topologically linked daughter chromosomes during the terminal stage of DNA replication.

What is the difference between topoisomerase 1 and 2?

Topoisomerase I refers to the enzymes which cut one of the two strands of double-stranded DNA, relax the strand, and reanneal the strand while topoisomerase II refers to the enzymes which cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils.

What happens if topoisomerase is not functional?

Topoisomerase alleviates supercoiling downstream of the origin of replication. In the absence of topoisomerase, supercoiling tension would increase to the point where DNA could fragment. DNA replication could not be initiated because there would be no RNA primer. DNA strands would not be ligated together.

Do humans have topoisomerase?

Topoisomerases are enzymes that resolve topological problems within the double helix by repeated cycles of DNA cleavage and ligation (1⇓–3, 5, 6). As a subclass of the topoisomerase family, type II topoisomerases are found in all organisms from bacteria to human, and even in some viruses (1⇓–3, 5, 6).

What causes supercoiling of DNA?

Supercoiling occurs when the molecule relieves the helical stress by twisting around itself. The hydrogen bonds (holding together complementary bases) break and part of the double helix separates. Strand separation is required for transcription (copying DNA to RNA) and replication (copying DNA to DNA).

What are the similarities between topoisomerase I and II?

Similarities Between Topoisomerase I and II 1 Topoisomerase I and II are two enzymes responsible for fixing topological problems of the DNA double helix. 2 They act upon both over winded and under winded DNA. 3 Moreover, their function is essential for the progression of DNA replication and transcription.

What kind of topoisomerase is found in E.coli?

For example, E. coli has two type I DNA topoisomerases (DNA topoisomerase I and DNA topoisomerase III) and two type II DNA topoisomerases (DNA topoisomerase II or gyrase and DNA topoisomerase IV) 3). The DNA topoisomerase subtypes (A, B or C) are differentiated by amino acid sequences or structures 4).

How is Topoisomerase IV used to treat catenanes?

Topoisomerase IV can unknot right-handed knots and decatenate right-handed catenanes without acting on right-handed plectonemes in negatively supercoiled DNA molecules, based on geometrical specificity of juxtapositions. Topoisomerase IV is also a target of antibiotics, such as the quinolone drugs, which include ciprofloxacin .

How are topoisomerase inhibitors used to treat duplex DNA?

TopI then re-ligates the cleaved strand to reestablish duplex DNA. Treatment with TopI inhibitors stabilizes the intermediate cleavable complex, preventing DNA re-ligation, and inducing lethal DNA strand breaks.