What is DNA topoisomerase?
DNA topoisomerases solve the topological problems associated with DNA replication, transcription, recombination, and chromatin remodeling by introducing temporary single- or double-strand breaks in the DNA.
What is the function of DNA topoisomerase III in E coli?
E. coli contains four DNA topoisomerases: two type IA enzymes (I and III), and two type IIA ( DNA gyrase and topoisomerase IV). DNA topoisomerase III and IV have similar functions. Topoisomerase III is incapable of relaxing positive supercoils, but it works to support replication fork movement on plasmid DNA in vitro.
How do topoisomerase inhibitors work to treat cancer?
Some chemotherapy drugs called topoisomerase inhibitors work by interfering with mammalian-type eukaryotic topoisomerases in cancer cells. This induces breaks in the DNA that ultimately lead to programmed cell death ( apoptosis ). This DNA-damaging effect, outside of its potential curative properties,…
What is archaeal topoisomerase V?
Archaeal topoisomerase V is the sole member of the newly established TopIC family. Although structurally distinct, this enzyme functionally resembles TopIB in terms of its mechanism of action; it forms a 3′-phosphotyrosyl intermediate and relaxes positive and negative supercoils.
What is the difference between IA and IB topoisomerase?
Type IA topoisomerases relax negatively supercoiled DNA and perform DNA decatenation, while type IB topoisomerases can relax both negatively and positively supercoiled DNA. Like the type IA topoisomerases, the type IIA topoisomerases exert their effect through a strand passage mechanism, in this case using what is known as a “two-gate” mechanism24.
How do topoisomerases correct the double helix?
In order to prevent and correct these types of topological problems caused by the double helix, topoisomerases bind to DNA and cut the phosphate backbone of either one or both the DNA strands.
How many types of DNA topoisomerases are there in E coli?
E. coli contains four DNA topoisomerases: two type IA enzymes (I and III), and two type IIA ( DNA gyrase and topoisomerase IV). DNA topoisomerase III and IV have similar functions.