Topoisomer: Difference between revisions

Latest revision as of 10:48, 15 February 2025

Topoisomer[edit]

A topoisomer is a type of isomer that differs in the topology of its molecular structure. Topoisomers are particularly important in the study of DNA, where they refer to different forms of DNA that have the same sequence but differ in their supercoiling or linking number.

DNA Topoisomers[edit]

DNA topoisomers are crucial in the context of DNA replication, transcription, and chromosome segregation. The double helix structure of DNA can become supercoiled, and the degree of supercoiling can affect the biological processes that involve DNA.

Types of DNA Topoisomers[edit]

DNA topoisomers can be classified based on their linking number, which is the number of times one strand of DNA winds around the other. The linking number is a topological property that remains constant unless the DNA is cut and rejoined.

Relaxed DNA: This form of DNA has no supercoiling and is in its most stable state.
Supercoiled DNA: This form of DNA is twisted upon itself, which can be either positive or negative supercoiling.

Enzymes Involved[edit]

Topoisomerases are enzymes that play a critical role in managing DNA topoisomers. They can cut one or both strands of DNA, allowing the DNA to be untangled or unwound, and then rejoin the strands.

Type I Topoisomerases: These enzymes cut one strand of DNA and allow it to rotate around the other strand, changing the linking number by increments of one.
Type II Topoisomerases: These enzymes cut both strands of DNA and pass another segment of the double helix through the break, changing the linking number by increments of two.

Biological Significance[edit]

The regulation of DNA topology is essential for maintaining the integrity of the genome during cell division and for the proper functioning of gene expression. Supercoiling can affect the accessibility of DNA to RNA polymerase and other transcription factors, influencing the rate of transcription.

Related pages[edit]

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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|Diagram of 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 a type of [[isomer]] that differs in the [[topology]] of its [[molecular structure]]. Topoisomers are particularly important in the study of [[DNA]], where they refer to different forms of DNA that have the same sequence but 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==
+DNA topoisomers are crucial in the context of [[DNA replication]], [[transcription]], and [[chromosome segregation]]. The [[double helix]] structure of DNA can become supercoiled, and the degree of supercoiling can affect the biological processes that involve DNA.
-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:
+=== Types of DNA Topoisomers ===
-. 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==
+DNA topoisomers can be classified based on their [[linking number]], which is the number of times one strand of DNA winds around the other. The linking number is a topological property that remains constant unless the DNA is cut and rejoined.
-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==
+* '''Relaxed DNA''': This form of DNA has no supercoiling and is in its most stable state.
-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.
+* '''Supercoiled DNA''': This form of DNA is twisted upon itself, which can be either positive or negative supercoiling.
+=== Enzymes Involved ===
+[[Topoisomerase]]s are enzymes that play a critical role in managing DNA topoisomers. They can cut one or both strands of DNA, allowing the DNA to be untangled or unwound, and then rejoin the strands.
+* '''Type I Topoisomerases''': These enzymes cut one strand of DNA and allow it to rotate around the other strand, changing the linking number by increments of one.
+* '''Type II Topoisomerases''': These enzymes cut both strands of DNA and pass another segment of the double helix through the break, changing the linking number by increments of two.
+== Biological Significance ==
+The regulation of DNA topology is essential for maintaining the integrity of the [[genome]] during cell division and for the proper functioning of [[gene expression]]. Supercoiling can affect the accessibility of DNA to [[RNA polymerase]] and other [[transcription factors]], influencing the rate of [[transcription]].
+== Related pages ==
+* [[DNA replication]]
+* [[Chromosome]]
+* [[Enzyme]]
+* [[Isomer]]
+* [[Supercoiling]]
-[[Category:Enzymes]]
-[[Category:DNA replication]]
 [[Category:Molecular biology]]
+[[Category:Genetics]]
-{{biology-stub}}