What does topoisomerase II do?
Topoisomerase II (topo II), which catalyzes a transient breakage and reunion of double-stranded DNA, was the first protein shown to be essential for mitotic chromosome condensation (Uemura et al., 1987).
What are the difference between the action of topoisomerase I and II?
While topoisomerase-I causes single-strand DNA breaks, topoisomerase-II itself induces transient double-strand DNA breaks. Topoisomerase-II is crucial for chromosome condensation and segregation, and cells that lack this enzyme are rendered unviable.
Does topoisomerase 2 require ATP?
Type II topoisomerases require free energy from ATP hydrolysis to maintain non-equilibrium product distributions, but as the free energy requirements are very small, it is perhaps unsurprising that we found the level of the effect to be independent of the free energy available from ATP hydrolysis, in experiments where …
Does topoisomerase II unwind DNA?
Class II DNA Topoisomerases � Break two strands of a DNA helix. � Topoisomerases II (gyrase), IV and VI. � ATP dependent. � Responsible for relaxing DNA (topoisomerase IV), as well as introducing either negative (topoisomerase II).
What is topoisomerase II alpha?
DNA topoisomerase II-alpha is the molecular target of doxorubicin, an active drug used in the therapy of breast cancer. From many in vitro studies, it is known that high levels of topo II-alpha expression correlate with drug sensitivity, and low levels of topo 11-alpha correlate with drug resistance.
How does topoisomerase relax supercoiled structures?
Of this enzyme class, topoisomerase type I enzymes cleave only one strand and resolve coils by swiveling the DNA around the remaining single phosphodiester backbone bond, while type II enzymes cut both strands to relax supercoiling.
How does DNA topoisomerase work?
DNA topoisomerases unravel twists in DNA that occur as a result of DNA transcription and replication. The DNA topoisomerases I and II present in cells act through scission of the DNA backbone on one or two strands, respectively, followed by relief of torsional stress and then relegation of the broken DNA backbone.
Does topoisomerase cut DNA?
Topoisomerases cut DNA to release tension created by twists and turns in the double helix. Typically, DNA is negatively supercoiled. This makes it easier to pull the two strands of DNA apart.
Why are topoisomerases important?
Topoisomerases. DNA topoisomerases are able to solve topological problems resulting from replication, transcription, recombination, and reorganization of the chromatin. Further on, topoisomerases change the state of supercoiling of the DNA and therefore, have great impact on gene activity.
What happens when topoisomerase II is inhibited?
Topoisomerase inhibitors block the ligation step of the cell cycle, which generates DNA single- and double-strand breaks, leading to apoptotic cell death.
What is the function of topoisomerase during DNA replication?
Topoisomerase also plays an important maintenance role during DNA replication. This enzyme prevents the DNA double helix ahead of the replication fork from getting too tightly wound as the DNA is opened up.
What role do topoisomerases play in DNA replication?
How does topoisomerase affect DNA replication?
Why is topoisomerase important to DNA replication?
What happens when you inhibit topoisomerase 2?
Topoisomerase inhibitors block the ligation step of the cell cycle, which generates DNA single- and double-strand breaks, leading to apoptotic cell death. Topoisomerase I inhibitors include irinotecan, topotecan, and camptothecin, and topoisomerase II inhibitors include etoposide, doxorubicin, and epirubicin.