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Supercoiled structure of circular DNA molecules with low writhe. The helical nature of the DNA duplex is omitted for clarity.Supercoiled structure of linear DNA molecules with constrained ends. The helical nature of the DNA duplex is omitted for clarity.
DNA supercoiling refers to the amount of twist in a particular DNA strand, which determines the amount of strain on it. A given strand may be "positively supercoiled" or "negatively supercoiled" (more or less tightly wound). The amount of a strand's supercoiling affects a number of biological processes, such as compacting DNA and regulating access to the genetic code (which strongly affects DNA metabolism and possibly gene expression). Certain enzymes, such as topoisomerases, change the amount of DNA supercoiling to facilitate functions such as DNA replication and transcription.[1] The amount of supercoiling in a given strand is described by a mathematical formula that compares it to a reference state known as "relaxed B-form" DNA.
^Bar, A.; Mukamel, D.; Kabakçoǧlu, A. (2011). "Denaturation of circular DNA: Supercoil mechanism". Physical Review E. 84 (4): 041935. arXiv:1108.5444. Bibcode:2011PhRvE..84d1935B. doi:10.1103/physreve.84.041935. PMID 22181203. S2CID 28666131.
This shape is referred to as a supercoil. (The noun form "supercoil" is often used when describing DNA topology.) The DNA of most organisms is usually negatively...
the introduction of negative supercoils into DNA and is the only type II enzyme to do this, all the others catalyze DNA relaxation. Type II enzymes are...
into some of the palindromes. Buoyant density centrifugation DNA profiling DNAsupercoil Eukaryotic chromosome fine structure Gene expression Polymerase...
bacteria, whose single circular DNA is cut by DNA gyrase and the two ends are then twisted around each other to form supercoils. Gyrase is also found in eukaryotic...
(including DNA gyrase) achieve this by adding negative supercoils to the DNA helix. Bare single-stranded DNA tends to fold back on itself forming secondary structures;...
other. In DNA this property does not change and can only be modified by specialized enzymes called topoisomerases. DNAsupercoil (superhelical DNA) Knot theory...
numbers when considering DNAsupercoils. In a paper published in 1976, Crick outlined the problem as follows: In considering supercoils formed by closed double-stranded...
supercoiled DNA, respectively. The handedness of the toroidal supercoils is opposite to those of plectonemes. Both plectonemes and toroidal supercoils can be...
DNA (dsDNA) breaks and reseals them after managing torsion of DNAsupercoils. Anthracyclines intercalated into DNA, form a stable anthracycline-DNA-topoisomerase...
junctions can arise to relieve helical strain in symmetrical sequences in DNAsupercoils. While four-arm junctions also appear in functional RNA molecules, such...
writhe number increases, introducing positive supercoils in the DNA. These supercoils would cause DNA replication to halt if they were not removed. Topoisomerases...
topoisomerases that cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils. They use the hydrolysis of ATP, unlike...
transcription and suppress pausing of Pol I. As Pol I proceeds along the rDNA, supercoils form both ahead of and behind the complex. These are unwound by topoisomerase...
supercoiled DNA, whereas eukaryotic topoisomerase I (topo IB) can introduce positive supercoils, separating the DNA of daughter chromosomes after DNA replication...
the DNA polymerase. As helicase unwinds the double helix, topological changes induced by the rotational motion of the helicase lead to supercoil formation...
unwinding and rewinding of DNA. Because regions of DNA in front of RNAP are unwound, there are compensatory positive supercoils. Regions behind RNAP are...
cellular reproduction and DNA organization, as they mediate the cleavage of single and double stranded DNA to relax supercoils, untangle catenanes, and...
supercoils, therefore, DNA Gyrase and topoisomerase IV play an almost identical role in removing the positive supercoils ahead of a translocating DNA...
two or more alpha helices that are wound around each other to form a supercoil. Coiled coils contain 3- and 4-residue repeats whose hydrophobicity pattern...
cell is to relax positive supercoils. It shares this role with DNA gyrase, which is also able to relax positive supercoils. Together, gyrase and topoisomerase...
cell division; and first ever study of the dynamics DNAsupercoils and the discovery of supercoil hopping 2013, controlled shaping of live bacterial cells...
open-circular DNA has one strand cut. Relaxed circular DNA is fully intact with both strands uncut but has been enzymatically relaxed (supercoils removed)...
cell cycle cohesin SMC protein ATPase HEAT repeat Topoisomerase II DNAsupercoil Hirano T (2016). "Condensin-based chromosome organization from bacteria...
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