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Topoisomerase
DNA topoisomerases (or topoisomerases) are enzymes that catalyze changes in the topological state of DNA, interconverting relaxed and supercoiled forms, linked (catenated) and unlinked species, and knotted and unknotted DNA. Topological issues in DNA arise due to the intertwined nature of its double-helical structure, which, for example, can lead to overwinding of the DNA duplex during DNA replication and transcription. If left unchanged, this torsion would eventually stop the DNA or RNA polymerases involved in these processes from continuing along the DNA helix. A second topological challenge results from the linking or tangling of DNA during replication. Left unresolved, links between replicated DNA will impede cell division. The DNA topoisomerases prevent and correct these types of topological problems. They do this by binding to DNA and cutting the sugar-phosphate backbone of either one (type I topoisomerases) or both (type II topoisomerases) of the DNA strands. This transien ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topoisomerase I
DNA topoisomerases (or topoisomerases) are enzymes that catalyze changes in the topological state of DNA, interconverting relaxed and supercoiled forms, linked (catenated) and unlinked species, and knotted and unknotted DNA. Topological issues in DNA arise due to the intertwined nature of its double-helical structure, which, for example, can lead to overwinding of the DNA duplex during DNA replication and transcription. If left unchanged, this torsion would eventually stop the DNA or RNA polymerases involved in these processes from continuing along the DNA helix. A second topological challenge results from the linking or tangling of DNA during replication. Left unresolved, links between replicated DNA will impede cell division. The DNA topoisomerases prevent and correct these types of topological problems. They do this by binding to DNA and cutting the sugar-phosphate backbone of either one (type I topoisomerases) or both (type II topoisomerases) of the DNA strands. This transien ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topoisomerase IV
Topoisomerase IV is one of two Type II topoisomerases in bacteria, the other being DNA gyrase. Like gyrase, topoisomerase IV is able to pass one double-strand of DNA through another double-strand of DNA, thereby changing the linking number of DNA by two in each enzymatic step. Both share a hetero-4-mer structure formed by a symmetric homodimer of A/B heterodimers, usually named ''ParC'' and ''ParE''. Functions Topoisomerase IV has two functions in the cell. * First, it is responsible for unlinking, or decatenating, DNA following DNA replication. The double-helical nature of DNA and its semiconservative mode of replication causes the two newly replicated DNA strands to be interlinked. These links must be removed in order for the chromosome (and plasmids) to segregate into daughter cells so that cell division can complete. * Topoisomerase IV's second function in the cell is to relax positive supercoils. It shares this role with DNA gyrase, which is also able to relax positive super ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TOP2A
DNA topoisomerase IIα is a human enzyme encoded by the ''TOP2A'' gene. Topoisomerase IIα relives topological DNA stress during transcription, condenses chromosomes, and separates chromatids. It catalyzes the transient breaking and rejoining of two strands of duplex DNA which allows the strands to pass through one another. Two forms of this enzyme exist as likely products of a gene duplication event. The gene encoding this form, alpha, is localized to chromosome 17 and the beta gene is localized to chromosome 3. The gene encoding this enzyme functions as the target for several chemotherapy agents and a variety of mutations in this gene have been associated with the development of drug resistance. Reduced activity of this enzyme may also play a role in ataxia-telangiectasia. Interactions TOP2A has been shown to interact with SMURF2, HDAC1, CDC5L, Small ubiquitin-related modifier 1, P53, and TOPBP1. In other species In ''Drosophila'' Hadlaczky et al 1988 found DNA topoisomeras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topoisomerase IIα
DNA topoisomerase IIα is a human enzyme encoded by the ''TOP2A'' gene. Topoisomerase IIα relives topological DNA stress during transcription, condenses chromosomes, and separates chromatids. It catalyzes the transient breaking and rejoining of two strands of duplex DNA which allows the strands to pass through one another. Two forms of this enzyme exist as likely products of a gene duplication event. The gene encoding this form, alpha, is localized to chromosome 17 and the beta gene is localized to chromosome 3. The gene encoding this enzyme functions as the target for several chemotherapy agents and a variety of mutations in this gene have been associated with the development of drug resistance. Reduced activity of this enzyme may also play a role in ataxia-telangiectasia. Interactions TOP2A has been shown to interact with SMURF2, HDAC1, CDC5L, Small ubiquitin-related modifier 1, P53, and TOPBP1. In other species In ''Drosophila'' Hadlaczky et al 1988 found DNA topoisomeras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Replication
In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential. DNA is made up of a double helix of two complementary strands. The double helix describes the appearance of a double-stranded DNA which is thus composed of two linear strands that run opposite to each other and twist together to form. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. As a result of semi-conservative rep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Gyrase
DNA gyrase, or simply gyrase, is an enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ... within the class of topoisomerase and is a subclass of Type II topoisomerases that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA polymerase, RNA-polymerase or by helicase in front of the progressing DNA replication#Replication fork, replication fork. The enzyme causes negative DNA supercoil, supercoiling of the DNA or relaxes positive supercoils. It does so by looping the template so as to form a crossing, then cutting one of the double helices and passing the other through it before releasing the break, changing the linking number by two in each enzymatic step. This process occurs in bacteria, whose single circular DNA is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TOP2B
DNA topoisomerase 2-beta is an enzyme that in humans is encoded by the ''TOP2B'' gene. Function This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This nuclear enzyme is involved in processes such as chromosome condensation, chromatid separation, and the relief of torsional stress that occurs during DNA transcription and replication. It catalyzes the transient breaking and rejoining of two strands of duplex DNA which allows the strands to pass through one another, thus altering the topology of DNA. Two forms of this enzyme exist as likely products of a gene duplication event. The gene encoding this form, beta, is localized to chromosome 3 and the alpha form is localized to chromosome 17. The gene encoding this enzyme functions as the target for several anticancer agents, for example mitoxantrone, and a variety of mutations in this gene have been associated with the development of drug resistance. Reduced a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Champoux
James J. Champoux (died 13 May 2019) was an American microbiologist who worked at University of Washington and an Elected Fellow of the American Association for the Advancement of Science. Education He earned his B.S. at University of Washington and his Ph.D. at Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider .... Research His interests were retroviruses and topoisomerases and his highest cited paper is ''DNA Topoisomerases: Structure, Function, and Mechanism'' at 2260 times, according to Google Scholar. Publications *Effects of DNA and protein size on substrate cleavage by human tyrosyl-DNA phosphodiesterase 1. Interthal H, Champoux JJ The Biochemical Journal. 2011 Jun; 436 3: 559-66 *Multiple nucleotide preferences determine cleavage-site recognition by the HIV- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topoisomerase IIβ
DNA topoisomerase 2-beta is an enzyme that in humans is encoded by the ''TOP2B'' gene. Function This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This nuclear enzyme is involved in processes such as chromosome condensation, chromatid separation, and the relief of torsional stress that occurs during DNA transcription and replication. It catalyzes the transient breaking and rejoining of two strands of duplex DNA which allows the strands to pass through one another, thus altering the topology of DNA. Two forms of this enzyme exist as likely products of a gene duplication event. The gene encoding this form, beta, is localized to chromosome 3 and the alpha form is localized to chromosome 17. The gene encoding this enzyme functions as the target for several anticancer agents, for example mitoxantrone, and a variety of mutations in this gene have been associated with the development of drug resistance. Reduced act ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topoisomerase IIIα
DNA topoisomerase 3-alpha is an enzyme that in humans is encoded by the ''TOP3A'' gene. Function This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This enzyme catalyzes the transient breaking and rejoining of a single strand of DNA which allows the strands to pass through one another, thus reducing the number of supercoils and altering the topology of DNA. This enzyme forms a complex with BLM which functions in the regulation of recombination in somatic cells. Meiosis Recombination during meiosis is often initiated by a DNA double-strand break (DSB). During recombination, sections of DNA at the 5' ends of the break are cut away in a process called ''resection''. In the ''strand invasion'' step that follows, an overhanging 3' end of the broken DNA molecule then "invades" the DNA of an homologous chromosome that is not broken forming a displacement loop (D-loop). After strand invasion, the further seque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TOP3A
DNA topoisomerase 3-alpha is an enzyme that in humans is encoded by the ''TOP3A'' gene. Function This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This enzyme catalyzes the transient breaking and rejoining of a single strand of DNA which allows the strands to pass through one another, thus reducing the number of supercoils and altering the topology of DNA. This enzyme forms a complex with BLM which functions in the regulation of recombination in somatic cells. Meiosis Recombination during meiosis is often initiated by a DNA double-strand break (DSB). During recombination, sections of DNA at the 5' ends of the break are cut away in a process called ''resection''. In the ''strand invasion'' step that follows, an overhanging 3' end of the broken DNA molecule then "invades" the DNA of an homologous chromosome that is not broken forming a displacement loop (D-loop). After strand invasion, the further seque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
