Supercoiling
Supercoiling - Related Videos
02:02
DNA Topoisomerases
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2020
Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA. Types and Mechanism of action Topoisomerases are divided into two main types. Type I...
12:19
Tools to Study the Role of Architectural Protein HMGB1 in the Processing of Helix Distorting, Site-specific DNA Interstrand Crosslinks
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2016
Targeted DNA damage can be achieved by tethering a DNA damaging agent to a triplex-forming oligonucleotide (TFO). Using modified TFOs, DNA damage-specific protein association, and DNA topology modification can be studied in human cells by the utilization of modified chromatin immunoprecipitation assays and DNA supercoiling assays described herein.
07:50
Detection and Removal of Nuclease Contamination During Purification of Recombinant Prototype Foamy Virus Integrase
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Cited by 10 •
2017
Recombinant prototype foamy virus integrase protein is often contaminated with a bacterial nuclease during purification. This method identifies nuclease contamination and removes it from the final preparation of the enzyme.
05:06
Alkaline Single Cell Gel Electrophoresis: A Sensitive Technique for Quantitative Estimation of DNA Damage in Individual Cancer Cells Following Chemotherapy
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2025
In this video, we demonstrate an alkaline single-cell electrophoresis assay to quantify both single- and double-strand DNA breaks in doxorubicin-treated cells. Alkaline conditions disrupt the hydrogen bonds between DNA base pairs, resulting in the complete unwinding and separation of DNA strands. This allows differential migration of undamaged and damaged DNA fragments in agarose gel upon electrophoresis, revealing a comet-shaped structure of slowly migrating undamaged DNA forming the circular...
11:01
Bacterial Transformation: The Heat Shock Method
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2023
Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of bacteria. In molecular biology, transformation is artificially reproduced in the lab via the creation of pores in bacterial cell membranes. Bacterial cells that are able to take up DNA from the environment are called competent cells. In the laboratory, bacterial cells can be made competent and DNA subsequently introduced by a procedure called...
FAQs
A change in linking number alters the DNA molecule’s torsional strain, producing either overwinding or underwinding. These states change how the double helix folds into higher-order structures and can modify the accessibility of particular DNA regions. Consequently, linking-number changes provide a physical mechanism through which cells organize genetic material and influence processes that require access to DNA.
Topoisomerases regulate DNA topology by transiently breaking and resealing DNA strands. This temporary strand passage allows them to relieve torsional strain or introduce it, depending on the cellular requirement. Their activity prevents topological stress from accumulating unchecked and makes them central to maintaining DNA structures compatible with chromosome organization, replication, transcription, and recombination.
Supercoiling changes the physical accessibility of DNA, so it can affect whether molecular machinery reaches particular genetic regions. Overwinding or underwinding modifies the local structural state of the double helix rather than simply changing its shape at a larger scale. These topology-dependent accessibility changes help connect DNA organization with regulation of genetic activity.
Researchers investigate supercoiling by measuring or deliberately manipulating DNA’s topological state, then examining the resulting structural or biological effects. Such experiments can test how changes in torsional strain influence genome organization, enzyme activity, or DNA accessibility. Comparing altered states with an appropriate reference allows investigators to associate specific outcomes with DNA topology.
Supercoiling contributes to chromosome compaction and influences replication, transcription, and recombination. Its effects arise because changes in DNA topology alter both the organization of genetic material and the accessibility of the double helix. Studying these relationships helps explain how cells coordinate DNA use with the physical constraints imposed by a compact genome.
Manipulating supercoiling can reveal how DNA topology contributes to genome organization, enzyme activity, and gene regulation. Researchers can use controlled changes in topological state to examine the consequences of torsional strain and altered accessibility. This approach also supports investigations of the mechanisms by which topoisomerases control DNA structure during essential genetic processes.