Last Updated on
September 19, 2022
Topoisomerase (DNA topoisomerases) is an enzyme that catalyzes the changes in the intertwined state of two DNA strands. It helps in vivo and in vitro DNA replication, transcription, chromosome segregation, and recombination.
It mainly facilitates the interconversion forms (also known as topological changes) of relaxed and supercoiled DNA, knotting and unknotting DNA, and linked (catenate) and unlinked (decatenate) species.
Naturally, the topological changes occur either due to intertwining in the helical structure of DNA or linking/tangling of the DNA helix during genome replication. However, they are corrected by the enzyme topoisomerase.
If left uncorrected, these issues can hinder cell division, DNA replication, and transcription (by preventing DNA and RNA polymerase enzymes from continuing along the helix) processes.
Topoisomerase was discovered in 1957 by the scientist J.C. Wang when he was working on Escherichia coli (or E.coli). Similar topoisomerase activity was observed by James Champoux and Renato Dulbecco in eukaryotic cells.
The enzyme works by breaking the phosphodiester bond present in the backbone of the two DNA strands. However, the broken bonds in the DNA molecules reform as soon as the topoisomerase enzyme leaves the strands.
In this article, we will review how topoisomerase works, its application in lab assays, and the industrial areas involving the use of these enzymes.
Topoisomerase is of two types: topo I and topo II. Both have different structures and functions. Have a look at what they are!
This is further divided into type IA, type IB (show homology to top I of human), and type IC. The only enzyme that introduces the positive supercoiling in DNA is a reverse gyrase enzyme, which is coupled with a helicase found in archaea and is a type IA topoisomerase.
There are three types: type IIa (examples are DNA gyrase, topoisomerase IV, and human topoisomerase IIɑ and II𝛃), Type IIb, and Type IIC. These all enzymes catalyze negative supercoiling in DNA.
Different types of topoisomerases have different action mechanisms based on their structure.
Some chemical compounds can inhibit the functional roles of topoisomerases in organisms. They commonly do it by hindering the DNA ligation step. Some examples of such chemicals are:
Topoisomerase has a myriad of in vivo and in vitro applications in a range of metabolic processes, such as DNA replication, transcription, chromosome segregation, and recombination.
DNA replication is the process of synthesizing a new strand of DNA using the old one as a template. During the process, the topoisomerase enzyme help in introducing positive supercoiling ahead of the replication fork and catenation behind the fork.
In a closed genome replication process, such as a plasmid, the topoisomerase enzyme introduces negative supercoiling at the origin. This facilitates the melting of the strands and exposes them to start the replication process.
Transcription is the synthesis of mRNA (or messenger RNA) by decoding information from the DNA strands. In this process, the topoisomerase enzyme helps introduce positive supercoiling ahead of the transcriptional complex and negative supercoiling behind it.
Double strand DNA breaks made by Topo IIβ and histone H-1 replacements are required to promote transcription. Furthermore, elements involved in DNA damage repair machinery are essential for gene expression and gene regulation.
Recombination is an exchange of genetic material between two chromosomes, leading to the formation of a different combination of genes. Topoisomerases are also integral components of the DNA repair complex. They are also involved in releasing knots formed during recombination.
Topoisomerases are required to maintain a proper structure of the chromosome. It also helps in chromosome condensation, segregation, and cohesion. Furthermore, topoisomerase enzymes have essential roles in chromatin remodeling and centromere functions.
Topoisomerases have vast applications in all essential in vivo metabolic processes. Thus, the enzyme is commercially prepared and sold for use in in vitro workflows. Below are some industries that extensively use topoisomerases.
In pharmaceuticals, topoisomerases are used as drug targets for antitumor or anti-cancer chemotherapy. However, its inhibitors are used as antibiotics and in various anticancer therapeutics other than chemotherapy.
Topoisomerases have a range of applications in biochem labs. They help in studies ranging from in vitro replication and transcription to chromosome segregation and recombination in organisms.
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Topoisomerases are enzymes that change DNA topology by breaking and relegating nucleic acid strands. The enzyme is also known as DNA topoisomerases as it has no function in RNA-related processes.
Topoisomerases are of two types: type I, which creates single-strand breaks, and type II, which facilitates double-strand breaks in DNA substrate. The functions performed by the enzyme include catenation and decatenation, DNA supercoiling (increase or decrease supercoiling), and relaxing in metabolic processes like replication, transcription, and recombination.
Because of their extensive roles in a myriad of metabolic processes, topoisomerase enzymes are essential tools used in pharmaceutical and biochem labs. The result of these workflows depends greatly on the quality of the enzyme — in addition to high-throughput equipment.
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