topoisomerase supercoilingtopoisomerase supercoiling

The alternative and simplest explanation for the increase of DNA knot formation is that (+)S compacts the nucleosomal fiber. The burst of DNA knot formation as a consequence of chromatin compaction also accounts for the differential effects of (+)S and ()S of DNA. If the pH is then lowered, the s value is not restored. (A) Beads-on-a-string model that simulates nucleosomal fibers. Examples of stochastic models that focus on the effects of PSB on a promoters activity can be found in: [21][22]. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. These changes in superhelicity are schematically illustrated by four little drawings which have been strategically superimposed upon the figure above. In a "relaxed" double-helical segment of B-DNA, the two strands twist around the helical axis once every 10.410.5 base pairs of sequence. Recent studies have revealed that the DNA cross-inversion mechanism of topoisomerase II (topo II) not only removes DNA supercoils and DNA replication intertwines, but also produces small amounts of DNA knots within the clusters of nucleosomes that conform to eukaryotic chromatin. Because DNA must be unwound for DNA/RNA polymerase action, supercoils will result. Absolute writhe (|Wr|) was computed by averaging the sum of the signed crossings (defined according to the right-hand rule after orienting the curve) over hundreds of projections. The two lobes of the figure eight will appear rotated either clockwise or counterclockwise with respect to one another, depending on whether the helix is over- or underwound. In response to supercoiling, they will assume an amount of writhe, just as if their ends were joined. So far, we have uncovered that the DNA knotting probability changes dramatically with chromatin dynamics. We next used this reference model of the nucleosomal fiber to generate millions of random conformers and profiled this unbiased sample in terms of the impact of compaction on knot probability. [3][4], For example, the researchers identified a specific sequence of DNA that regulates transcription speed; as the amount of supercoil rises and falls, it slows or speeds the pace at which molecular machinery reads DNA. However, there may be complementary changes in Tw and Wr without changing their sum: Tw, called "twist," is the number of WatsonCrick twists in the chromosome when it is not constrained to lie in a plane. Topoisomerase V relaxes supercoiled DNA by a constrained - PNAS Writhe has the effect of changing the apparent Linkage number. These enzymes are widely conserved, sharing >91% amino acid identity between the closely related species Escherichia coli and Salmonella enterica serovar Typhimurium. Because the length of DNA can be thousands of times that of a cell, packaging this genetic material into the cell or nucleus (in eukaryotes) is a difficult feat. These SMC proteins induce positive supercoils. This requirement affects long genes involved in neural development (20) and synaptic function (23) and linked to autism (24). Antonio Valds and others, Transcriptional supercoiling boosts topoisomerase II-mediated knotting of intracellular DNA, Nucleic Acids Research, Volume 47, Issue 13, 26 July 2019, Pages 69466955, https://doi.org/10.1093/nar/gkz491. Negative supercoiling is also thought to favour the transition between B-DNA and Z-DNA, and moderate the interactions of DNA binding proteins involved in gene regulation.[19]. It helps in vivo and in vitro DNA replication, transcription, chromosome segregation, and recombination. In this respect, the activity of intracellular topoisomerases has been found to relax (+)S domains faster than ()S domains (19). These observations led us to hypothesize that the constraints impairing transcription elongation could be DNA knots (i.e. As stated previously, the structure of Form IV is almost entirely unknown, and there is no currently accepted explanation for its extraordinary density. Substrate depletion and catenated DNA production can be evaluated by agarose gel electrophoresis. Positive DNA supercoiling becomes possible through the functional cooperation of the N-terminal helicase domain of reverse gyrase with its C-terminal type IA topoisomerase domain. Tel: +34 9340 20117; Email: Supercoiling of the DNA template during transcription, Supercoiling of intracellular DNA can occur in eukaryotic cells, New mechanistic and functional insights into DNA topoisomerases, Roles of eukaryotic topoisomerases in transcription, replication and genomic stability, A model for the mechanism of human topoisomerase I. 0 We then computed the knot probability of rings of 25 beads as a function of D/L. In this case, the typical Lk distribution constrained by native nucleosomes (top gel, lane 1) was shifted entirely clockwise after the thermal inactivation of topo II (lane 2), denoting the accumulation of (+)S in all the minichromosomes. YRp4) was matched by a D/L ratio of 0.47 (Figure 6B). If DNA is underwound, it will be under strain, exactly as a metal spring is strained when forcefully unwound, and that the appearance of supertwists will allow the chromosome to relieve its strain by taking on negative supertwists, which correct the secondary underwinding in accordance with the topology equation above. Rg reduction correlated to increasing values of |Wr|, and the compaction levels needed to obtain the knot spectrum induced by (+)S in vivo involved |Wr| values 9. Sperling A.S., Jeong K.S., Kitada T., Grunstein M. Bermudez I., Garcia-Martinez J., Perez-Ortin J.E., Roca J. Kouzine F., Gupta A., Baranello L., Wojtowicz D., Ben-Aissa K., Liu J., Przytycka T.M., Levens D. Naughton C., Avlonitis N., Corless S., Prendergast J.G., Mati I.K., Eijk P.P., Cockroft S.L., Bradley M., Ylstra B., Gilbert N. Fernandez X., Diaz-Ingelmo O., Martinez-Garcia B., Roca J. Lyu Y.L., Lin C.P., Azarova A.M., Cai L., Wang J.C., Liu L.F. Solier S., Ryan M.C., Martin S.E., Varma S., Kohn K.W., Liu H., Zeeberg B.R., Pommier Y. Mabb A.M., Kullmann P.H., Twomey M.A., Miriyala J., Philpot B.D., Zylka M.J. King I.F., Yandava C.N., Mabb A.M., Hsiao J.S., Huang H.S., Pearson B.L., Calabrese J.M., Starmer J., Parker J.S., Magnuson T. et al. "Form I" (blue curve) is the traditional nomenclature used for the native form of duplex circular DNA, as recovered from viruses and intracellular plasmids. In previous studies, we showed that no significant changes of PKn occur in top1 or top24 cells, at either 26 or 37C (27). As in previous studies, we used yeast circular minichromosomes to analyze DNA knot formation in intracellular chromatin (27). Such a contortion is a supercoil. They are further subdivided into two structurally and mechanistically distinct topoisomerases: type IA and type IB. Finally, we asked how the compaction levels inferred from the simulation would correlate to DNA supercoiling. The topology of DNA can be described by three parameters: For circularly closed DNA, like the E. coli genome, the linking number can only be changed if we do the following: Figure 1.6.1: Turns to change the linking number. Previous studies indicate that mitotic chromosomes are shaped by topo II-sensitive DNA entanglements (58), and that topo II activity is required for both resolution and formation of facultative heterochromatin (59). For instance, ()S could promote the formation of extended RNA/DNA hybrids (54), which could preclude the activity of topo II (55). Conflict of interest statement. Single-molecule analysis of DNA uncoiling by a type II topoisomerase To reach the PKn of 0.5 produced by (+)S in vivo, Rg had to be reduced more than 60% relative to Rg0, corresponding thus to a 5-fold volume compaction. However, if (+)S levels remain elevated or topoisomerase activity is altered, DNA knots could then persist and obstruct DNA transcription and chromatin assembly, as it has been demonstrated in vitro with knotted DNA templates (26,57). Circular minichromosomes YRp4 (27), YEp24 (27) and pYR121 (29) were amplified as bacterial plasmids in E. coli and used to transform S. cerevisiae following standard procedures. As a general rule, the DNA of most organisms is negatively supercoiled. We show that (+)S increases topo II-mediated knotting of DNA over 25-fold and that this increase is consequent to chromatin compaction. Please check for further notifications by email. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Finally, there needs to be a means to quantify PSB on the DNA (i.e. The Simian Virus 40 (SV40) genome is a circular, closed, double stranded DNA genome. Supporting this notion, topo II produces in vitro abundant and complex knots when DNA is compacted by supercoiling or other condensing agents (3537). DNA has a preferred "Twist" value (preferred apparent linkage number) for a specified length of DNA: For a given (fixed) Linkage number over a given length of DNA, the DNA can adopt either positive or negative supercoils to achieve a "twist" (apparent linkage number) such that there will be 10.6 basepairs/turn. The above example illustrates that twist and writhe are interconvertible. We would like to show you a description here but the site won't allow us. This page titled 7.2B: Supercoiling is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Boundless. Your comment will be reviewed and published at the journal's discretion. The possibility that ()S was inhibiting DNA knotting by means of other mechanisms then seems unlikely. These results indicated that the boost of DNA knotting observed upon accumulation of (+)S in top1 top24 TopA+ can also occur during normal transcriptional supercoiling of DNA in TOP1 TOP2 cells. This dark side of the topo II activity should therefore be taken into account when interpreting structural and functional alterations of intracellular chromatin. To obtain a representative beads-on-a-string model of the nucleosomal fiber, we generated random conformations of rings of N beads (nucleosomes) of diameter D connected by straight infinitely thin segments of length L (DNA linker) (Figure 6A). Stewart L., Redinbo M.R., Qiu X., Hol W.G., Champoux J.J. Vos S.M., Tretter E.M., Schmidt B.H., Berger J.M. As a general rule, the DNA of most organisms is negatively supercoiled. Because DNA must be unwound for DNA and RNA polymerase action, supercoils will result. 2D-electrophoreses of 2-micron circles, YEp24 and pYR121 were carried out in 0.6% agarose (2-micron) or 0.45% agarose (YEp24 and pYR121) in TBE buffer at 25 V for 40 h in the first dimension, and at 125 V for 4 h in the second dimension. Here, we examine how transcriptional supercoiling of intracellular DNA affects the occurrence of these knots. (C and D) DNA topology of YRp4 in top1 top24 (C) and in top1 top24 TopA+ (D) cells. The probability of knot 31 increased 12 times, that of knot 41 25 times and that of knots 51 + 52 over 60 times (Figure 4D). The 3' end of the nick then passes once through the duplex. A negatively supercoiled DNA molecule will produce either a one-start left-handed helix, the toroid, or a two-start right-handed helix with terminal loops, the plectoneme. (A) DNA supercoiling and knotting of YRp4 in top1 top24 TopA+ cells sampled at different time points (min) after shifting the cultures to 37C. PKn did not change significantly with ()S, but increased 10-fold with (+)S (Figure 2F). This can therefore result in the removal of. Behind the complex, DNA is rewound and there will be compensatory negative supercoils. The separated single strands have slightly different s values, but display no significant changes in s with further increases in pH. We then plotted the knot probability obtained for max Rg values relative to Rg0, the gyration radius of the unconstrained distribution of conformers (Figure 6C). Negative DNA supercoiling allows chromosome condensation and facilitates DNA unwinding, which is required for the occurrence of DNA transaction processes, i.e., DNA replication, transcription and recombination. The Knotscape software (http://pzacad.pitzer.edu/jhoste/hostewebpages/kntscp.html) was used for this purpose. Type II topoisomerase - Wikipedia To examine the DNA knots formed in the minichromosomes, their DNA were nicked with endonuclease BstNBI and loaded in a 20 cm 20 cm agarose gel. (A) During normal DNA transcription, (+)S compacts chromatin and increases topo II-mediated knotting of DNA. DNA gyrase - Wikipedia To substantiate further the correlation of (+)S and knot formation, we compared the accumulation rate of (+)S molecules with that of knotted molecules by sampling the cells at different time points after inducing topo II inactivation (Figure 4A). For Form II, alterations in pH have very little effect on s. Its physical properties are, in general, identical to those of linear DNA. L.C and C.M. in bacterial gene expression), differing in, e.g., the level of detail. JCW28 carries the null mutation top1 and the thermosensitive mutation top24 (28). Moreover, high levels of (+)S may occur when transcribing complexes encounter twist diffusion barriers or converge with other transcribing units or replication forks. To this end, we analyzed DNA knotting in a minichromosome (pRY121), in which high rates of bidirectional transcription are induced from the galactose-inducible GAL1GAL10 divergent promoter (29). (D) Enhancement of individual knot populations by the effect of compaction. . Yeast cells were grown at 26C in yeast synthetic media containing adequate dropout supplements and 2% glucose. A Metropolis Monte Carlo scheme based on crankshaft moves was used to evolve the system, which was initially prepared in a circular arrangement. . Remarkably, this increase of knot formation occurred with no net accumulation of (+)S or ()S (Figure 5C), in agreement thus with the coexistence of twin supercoiled domains (Figure 5A). It becomes temporarily positively supercoiled when it is being replicated or transcribed. Data in panel (F) are presented as mean SD of three experiments. None declared. In nature, circular DNA is always isolated as a higher-order helix-upon-a-helix, known as a superhelix. Does Topoisomerase I relax all supercoiled DNA to the same degree - NEB Type I topoisomerase - Wikipedia However, the signals of DNA knots did not significantly change with the generation of ()S (bottom gel, compare lanes 1 and 2). Function. We demonstrated that DNA topoisomerase IV, acting in concert with topoisomerase I and gyrase, makes an important contribution to the steady-state level of supercoiling in Escherichia coli. Functional Analyses of the Toxoplasma gondii DNA Gyrase Holoenzyme: A Janus Topoisomerase with Supercoiling and Decatenation Abilities. 2D-electrophoreses of YEp24 and pRY121 were carried out in 0.6% agarose in TBE buffer plus 0.6 g/ml of chloroquine at 30 V for 36 h in the first dimension, and TBE buffer plus 3 g/ml of chloroquine, at 80 V for 4 h in the second dimension. The concurrence of DNA supercoiling and knotting might also account for the effects of topoisomerase dysfunction during the transcription of long genes in mammal cells (2024). The noun form supercoil is rarely used in the context of DNA topology. The "relaxed" structure on the left is not found unless the chromosome is nicked; the superhelix is the form usually found in nature. In this respect, since interphase chromatin has a scaling behavior not dissimilar to that of a fractal globule (50,51), there is very little intermingling and so possible entanglements of DNA across topologically associating domains(TADs) and other high-order folds of chromatin (52,53). Meanwhile, reactions 2 to 4 model, respectively, translation, and RNA and protein degradation.[13]. Funding for open access charge:Plan Estatal de Investigacin Cientfica y Tcnica of Spain [BFU2015-67007-P]. Apparent linkage number (Twist) = (5200 base pairs) / (10.6 base pairs/turn). Transcription forms and remodels supercoiling domains - Nature Cells were sampled at 26C (lane 1) and following 120 min at 37C (lane 2). If one goes around the superhelically twisted chromosome, counting secondary WatsonCrick twists, that number will be different from the number counted when the chromosome is constrained to lie flat. The amount of a strands 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). No supercoiling is relaxed, but stabilization and destabilization of a single DNA loop results in a change of the system's extension. The change in the linking number, Lk, is the actual number of turns in the plasmid/molecule, Lk, minus the number of turns in the relaxed plasmid/molecule Lko: If the DNA is negatively supercoiled, bacterial DNA gyrase) in eukaryotic cells (19). As a result, they may be unable to distribute excess twist to the rest of the chromosome or to absorb twist to recover from underwindingthe segments may become supercoiled, in other words. If a DNA segment under twist strain were closed into a circle by joining its two ends and then allowed to move freely, the circular DNA would contort into a new shape, such as a simple figure-eight. Then T ~ 40. Type II topoisomerases actually cleave the duplex DNA in changing the linkage number. This asymmetry in the conformational response of chromatin to helical tension of DNA has already explained why topo II is more proficient in relaxing (+)S than ()S in vivo (9,19). In vitro studies have shown that DNA over-twisting compacts nucleosomal fibers quicker and further than DNA untwisting (38,39). The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Upon relaxation of (+)S, topo II dissolves DNA knots and transcription can continue. Instead, global contortions of a circular DNA, such as the rotation of the figure-eight lobes above, are referred to as writhe. Arsuaga J., Vazquez M., Trigueros S., Sumners D., Roca J. Micheletti C., Marenduzzo D., Orlandini E., Sumners D.W. Marenduzzo D., Micheletti C., Orlandini E. Rybenkov V.V., Ullsperger C., Vologodskii A.V., Cozzarelli N.R. For example, if a secondary "WatsonCrick" twist is removed, then a right-handed supertwist must have been removed simultaneously (or, if the chromosome is relaxed, with no supertwists, then a left-handed supertwist must be added). Supercoiled DNA forms two structures; a plectoneme or a toroid, or a combination of both. Many topoisomerase enzymes sense supercoiling and either generate or dissipate it as they change DNA topology. PICH and TRR introduce a high density of positive supercoiling. Knots 31, 41, 51 and 52 are depicted. (B) The mechanism of topo II can produce and remove DNA knots by inverting juxtapositions of DNA linker segments (*) within nucleosomal fibers. In standard texts, these properties are invariably explained in terms of a helical model for DNA, but in 2008 it was noted that each topoisomer, negative or positive, adopts a unique and surprisingly wide distribution of three-dimensional conformations.[4]. Supercoiled DNA forms two structures; a plectoneme or a toroid, or a combination of both. A complete explanation for these data is beyond the scope of this article. Our findings indicate that topo II-mediated DNA knotting could be inherent to transcriptional supercoiling of DNA and other chromatin condensation processes and establish, therefore, a new crucial role of topoisomerase II in resetting the knottingunknotting homeostasis of DNA during chromatin dynamics. Published by Oxford University Press on behalf of Nucleic Acids Research. Also, transcription itself contorts DNA in living human cells, tightening some parts of the coil and loosening it in others. : any of a class of enzymes that reduce supercoiling in DNA by breaking and rejoining one or both strands of the DNA molecule Example Sentences Recent Examples on the Web When things start getting too tightly wound, topoisomerase cuts the DNA strand, unwinds it, and reattaches it with a bit more slack. The 5' phosphate of the nicked strand is covalently attached to a tyrosine in the protein. In bacteria, global DNA supercoiling results from the opposing activities of topoisomerase I, which relaxes DNA, and DNA gyrase, which compacts DNA. Each point computes the PKn of those configurations of Rg below a cutoff value (max Rg) relative to the average gyration radius of the entire distribution of conformers (Rg0). Based on this, a stochastic model of this process has been proposed. DNA packaging is greatly increased during nuclear division events such as mitosis or meiosis, where DNA must be compacted and segregated to daughter cells. (E) Incubation of the nicked DNA sample of (+)S YRp4 (no E) with topo I and topo II activities in vitro. we would expect 500 360 turns of the DNA strands over the length of the circular genome. "Positive" is referenced as right-handed. Gyrase is an enzyme that acts similarly to human Type II topoisomerase. We corroborated that the increased signals were knots of double-stranded DNA by incubating the sample with topo I and topo II in vitro. Effects of DNA supercoiling on chromatin architecture The burst of DNA knots induced by (+)S in intracellular chromatin was not anticipated by previous theoretical models of the effect of supercoiling on knot formation and resolution. From top-to-bottom they are: "Form IV" (green), "Form I" (blue) and "Form II" (red). Moreover, they discovered that the DNA sequence itself affects how the molecule responds to supercoiling. [11][12], Simply twisting DNA can expose internal bases to the outside, without the aid of any proteins. PMID: 29547555 PMCID: PMC5877745 DOI: 10.3390/ijms19030884 Abstract Although our knowledge of chromatin organization has advanced significantly in recent years, much about the relationships between different features of genome architecture is still unknown. Topoisomerase: Overview & Applications - Excedr Data in panels (B), (G) and (H) are presented as mean SD of three experiments. We therefore decided to monitor changes in the incorporation of biotinylated psoralen (bio-psoralen) ( Figure S6 D), a compound that preferentially intercalates into negatively supercoiled () DNA ( Bermdez et al . DNA supercoiling differences in bacteria result from disparate - PLOS [13] Moreover, during cold shocks, the density of nucleoids increases, and the protein gyrase and the nucleoid become colocalized (which is consistent with a reduction in DNA relaxation). . (B) Relative position of unknotted (N) and knotted nicked DNA circles (Kn) in a 2D-gel electrophoresis. k (A) Both topo I and topo II can relax the (+)S and ()S of DNA generated, respectively, in front of and behind the transcribing complex. DNA Supercoiling, Topoisomerases, and Cohesin: Partners in - PubMed Recent studies have revealed that the DNA cross-inversion mechanism of topoisomerase II (topo II) not only removes DNA supercoils and DNA replication intertwines, but also produces small amounts of DNA knots within the clusters of nucleosomes that conform to eukaryotic chromatin. Lko, the number of turns in the relaxed (B type) DNA plasmid/molecule, is determined by dividing the total base pairs of the molecule by the relaxed bp/turn which, depending on reference is 10.4;[14] 10.5;[15][16] 10.6.[17]. The titration ends at pH 13, where Form IV appears. In this respect, an interesting possibility is that DNA knotting might be exploited to stabilize specific chromatin conformations. When indicated, JCW25 and JCW28 were transformed with pJRW13, a plasmid that carries the Escherichia coli TopA gene under the constitutive pGPD yeast promoter (9). Type II topoisomerases increase or decrease the linking number of a DNA loop by 2 units, and it promotes chromosome disentanglement. Some stochastic models have been proposed to account for the effects of positive supercoiling buildup (PSB) in gene expression dynamics (e.g. Study reveals DNA supercoiling is involved in regulating - Research Now, count how many times the strands of the "duplex" cross each other. Introduction In . Supercoiling is important in a number of biological processes, such as compacting DNA. Since biological circular DNA is usually underwound, Lk will generally be less than Tw, which means that Wr will typically be negative. Supercoiling requires energy because it is torsionally strained. Stevens T.J., Lando D., Basu S., Atkinson L.P., Cao Y., Lee S.F., Leeb M., Wohlfahrt K.J., Boucher W., O'Shaughnessy-Kirwan A. et al. The duplex can exist with a twist of 10.6 bp/turn for most of the structure, and then have, As the replication fork opens up, the region of the duplex in front of the fork becomes. Form IV (green curve) is the product of alkali denaturation of Form I. It has been shown that condensin, a large protein complex that plays a central role in mitotic chromosome assembly, induces positive supercoils in an ATP hydrolysis-dependent manner in vitro. 1.6: DNA Supercoiling and Topoisomerases - Biology LibreTexts Transcriptional supercoiling boosts topoisomerase II-mediated knotting About all that is known about the tertiary structure is that it is duplex, but has no hydrogen bonding between bases. { "1.1:_DNA_as_Genetic_Material" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "1.2:_Structure_of_DNA_and_RNA" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "1.3:_Bacterial_Restriction_Modification_system" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "1.4:_DNA_Modifying_Enzymes" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "1.5:_DNA_Replication_-_Introduction_to_Prokaryotic_replication" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "1.6:_DNA_Supercoiling_and_Topoisomerases" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()" }, { "00:_Front_Matter" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "1:_DNA" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "2:_Bacteria" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "3._Biotechnology_1" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "4._Biotechnology_2" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "5._Lab_Notes_Part_1" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "6._Lab_Notes_Part_2" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "zz:_Back_Matter" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()" }, [ "article:topic", "showtoc:no", "authorname:mblaber" ], https://bio.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fbio.libretexts.org%2FBookshelves%2FBiochemistry%2FSupplemental_Modules_(Biochemistry)%2F1%253A_DNA%2F1.6%253A_DNA_Supercoiling_and_Topoisomerases, \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}}}\) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\), 1.5: DNA Replication - Introduction to Prokaryotic replication.