Topoisomer: Difference between revisions

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Topoisomer

A topoisomer is one of a set of molecules that have the same chemical formula and stereochemistry but differ in the topology of their molecular structure. Topoisomers are particularly important in the study of DNA, where they refer to different forms of DNA that differ in their supercoiling or linking number.

DNA Topoisomers

In the context of DNA, topoisomers are DNA molecules that have the same sequence but differ in their topological properties. DNA can exist in various topological forms, such as relaxed, supercoiled, or knotted. These forms are interconvertible through the action of topoisomerase enzymes, which can cut and rejoin the DNA strands to change the linking number.

Supercoiling

Supercoiling refers to the over- or under-winding of a DNA strand, and is an important aspect of DNA topology. Supercoiling is a natural state of DNA in cells and is crucial for DNA compaction and regulation of gene expression. DNA topoisomers with different degrees of supercoiling can be separated by gel electrophoresis, as they migrate differently due to their distinct shapes and sizes.

Topoisomerases

Topoisomerases are enzymes that play a critical role in managing DNA topology. They can introduce or remove supercoils by transiently breaking one or both strands of the DNA, allowing the DNA to be untwisted or untangled, and then resealing the breaks. There are two main types of topoisomerases: Type I, which cut one strand of DNA, and Type II, which cut both strands.

Applications and Importance

Understanding DNA topoisomers is essential in molecular biology and genetics. The study of DNA topology is important for understanding processes such as DNA replication, transcription, and chromosome segregation. Topoisomerases are also targets for certain antibiotics and anticancer drugs, making them significant in medicine.

Related pages

References

Bates, A. D., & Maxwell, A. (2005). DNA Topology. Oxford University Press.
Wang, J. C. (1996). DNA Topoisomerases. Annual Review of Biochemistry, 65, 635-692.

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-'''Topoisomerase''' is an [[enzyme]] that plays a crucial role in the processes of [[DNA replication]], [[transcription]], [[recombination]], and [[chromosome]] segregation. These enzymes modulate the topological states of DNA in cells by creating transient breaks in the DNA strands, thereby allowing the passage of another DNA helix and resolving supercoils or knots. This action is essential for the maintenance of genomic integrity and the prevention of DNA damage during cellular processes that involve the unwinding and rewinding of the DNA helix.
+== Topoisomer ==
-==Types of Topoisomerases==
+[[File:DNA_Topoisomers.png|thumb|right|300px|Illustration of different DNA topoisomers.]]
-Topoisomerases are broadly classified into two main types based on their mechanism of action:
-* '''Type I Topoisomerases''' ([[Topoisomerase I]]): These enzymes create transient single-strand breaks in DNA, allowing the passage of the unbroken strand through the break. This action relaxes the DNA helix without the need for [[ATP]] hydrolysis. Type I topoisomerases are further subdivided into Type IA and Type IB, based on differences in their structure and the specific mechanisms by which they cleave and rejoin the DNA strands.
+A '''topoisomer''' is one of a set of [[molecule]]s that have the same chemical formula and [[stereochemistry]] but differ in the [[topology]] of their [[molecular structure]]. Topoisomers are particularly important in the study of [[DNA]], where they refer to different forms of DNA that differ in their [[supercoiling]] or [[linking number]].
-* '''Type II Topoisomerases''' ([[Topoisomerase II]]): These enzymes create transient double-strand breaks in DNA, allowing the passage of another double-stranded DNA helix through the break. This process requires ATP hydrolysis and is crucial for resolving DNA tangles and supercoils that can occur during DNA replication and transcription. Type II topoisomerases are also involved in segregating newly replicated chromosomes during [[cell division]]. They are further divided into Type IIA and Type IIB, based on their structural and mechanistic differences.
+== DNA Topoisomers ==
-==Function and Mechanism==
+In the context of [[DNA]], topoisomers are DNA molecules that have the same sequence but differ in their [[topological]] properties. DNA can exist in various topological forms, such as relaxed, supercoiled, or knotted. These forms are interconvertible through the action of [[topoisomerase]] enzymes, which can cut and rejoin the DNA strands to change the linking number.
-The primary function of topoisomerases is to manage DNA supercoiling and ensure the proper functioning of cellular processes that involve DNA manipulation. By controlling the topological states of DNA, topoisomerases prevent the accumulation of supercoils, knots, and tangles that can interfere with DNA replication, transcription, and segregation.
-The mechanism of action for topoisomerases involves several steps:
+=== Supercoiling ===
-. Binding to DNA at specific sites.
-. Cleavage of one or both DNA strands, depending on the type of topoisomerase.
-. Passage of another segment of DNA through the break.
-. Re-ligation of the DNA strands to restore the integrity of the DNA molecule.
-==Clinical Significance==
+[[Supercoiling]] refers to the over- or under-winding of a DNA strand, and is an important aspect of DNA topology. Supercoiling is a natural state of DNA in cells and is crucial for DNA [[compaction]] and [[regulation]] of [[gene expression]]. DNA topoisomers with different degrees of supercoiling can be separated by [[gel electrophoresis]], as they migrate differently due to their distinct shapes and sizes.
-Topoisomerases are targets for several [[antibiotic]]s and [[anticancer drugs]]. Inhibitors of topoisomerases can interfere with DNA replication and transcription, leading to cell death. This property is exploited in cancer therapy to kill rapidly dividing tumor cells. However, the use of topoisomerase inhibitors can also lead to side effects due to their effects on normal cells.
-==Research and Future Directions==
+=== Topoisomerases ===
-Research on topoisomerases continues to uncover their complex roles in DNA dynamics and cellular processes. Understanding the precise mechanisms by which topoisomerases function and are regulated offers potential for the development of new therapeutic strategies for treating cancer and other diseases associated with DNA damage and genomic instability.
+[[Topoisomerase]]s are enzymes that play a critical role in managing DNA topology. They can introduce or remove supercoils by transiently breaking one or both strands of the DNA, allowing the DNA to be untwisted or untangled, and then resealing the breaks. There are two main types of topoisomerases: Type I, which cut one strand of DNA, and Type II, which cut both strands.
+== Applications and Importance ==
+Understanding DNA topoisomers is essential in [[molecular biology]] and [[genetics]]. The study of DNA topology is important for understanding processes such as [[DNA replication]], [[transcription]], and [[chromosome segregation]]. Topoisomerases are also targets for certain [[antibiotics]] and [[anticancer]] drugs, making them significant in [[medicine]].
+== Related pages ==
+* [[DNA topology]]
+* [[Topoisomerase]]
+* [[Supercoiling]]
+* [[Molecular biology]]
+== References ==
+* Bates, A. D., & Maxwell, A. (2005). DNA Topology. Oxford University Press.
+* Wang, J. C. (1996). DNA Topoisomerases. Annual Review of Biochemistry, 65, 635-692.
-[[Category:Enzymes]]
-[[Category:DNA replication]]
 [[Category:Molecular biology]]
+[[Category:DNA]]
-{{biology-stub}}