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Endonuclease
In molecular biology, endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain (namely DNA or RNA). Some, such as deoxyribonuclease I, cut DNA relatively nonspecifically (with regard to sequence), while many, typically called '' restriction endonucleases'' or ''restriction enzymes'', cleave only at very specific nucleotide sequences. Endonucleases differ from exonucleases, which cleave the ends of recognition sequences instead of the middle (''endo'') portion. Some enzymes known as "exo-endonucleases", however, are not limited to either nuclease function, displaying qualities that are both endo- and exo-like. Evidence suggests that endonuclease activity experiences a lag compared to exonuclease activity. Restriction enzymes are endonucleases from eubacteria and archaea that recognize a specific DNA sequence. The nucleotide sequence recognized for cleavage by a restriction enzyme is called the ''restriction site''. Typically, a restriction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endonucleases
In molecular biology, endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain (namely DNA or RNA). Some, such as deoxyribonuclease I, cut DNA relatively nonspecifically (with regard to sequence), while many, typically called '' restriction endonucleases'' or ''restriction enzymes'', cleave only at very specific nucleotide sequences. Endonucleases differ from exonucleases, which cleave the ends of recognition sequences instead of the middle (''endo'') portion. Some enzymes known as "exo-endonucleases", however, are not limited to either nuclease function, displaying qualities that are both endo- and exo-like. Evidence suggests that endonuclease activity experiences a lag compared to exonuclease activity. Restriction enzymes are endonucleases from eubacteria and archaea that recognize a specific DNA sequence. The nucleotide sequence recognized for cleavage by a restriction enzyme is called the ''restriction site''. Typically, a restriction site w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Restriction Enzyme
A restriction enzyme, restriction endonuclease, REase, ENase or'' restrictase '' is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. Restriction enzymes are one class of the broader endonuclease group of enzymes. Restriction enzymes are commonly classified into five types, which differ in their structure and whether they cut their DNA enzyme substrate (biology), substrate at their recognition site, or if the recognition and cleavage sites are separate from one another. To cut DNA, all restriction enzymes make two incisions, once through each backbone chain, sugar-phosphate backbone (i.e. each strand) of the DNA double helix. These enzymes are found in bacteria and archaea and provide a defense mechanism against invading viruses. Inside a prokaryote, the restriction enzymes selectively cut up ''foreign'' DNA in a process called ''restriction digestion''; meanwhile, host DNA is protected by a modification ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AP Endonuclease
Apurinic/apyrimidinic (AP) endonuclease is an enzyme that is involved in the DNA base excision repair pathway (BER). Its main role in the repair of damaged or mismatched nucleotides in DNA is to create a nick in the phosphodiester backbone of the AP site created when DNA glycosylase removes the damaged base. There are four types of AP endonucleases that have been classified according to their mechanism and site of incision. Class I AP endonucleases () cleave 3′ to AP sites by a β-lyase mechanism, leaving an unsaturated aldehyde, termed a 3′-(4-hydroxy-5-phospho-2-pentenal) residue, and a 5′-phosphate. Class II AP endonucleases incise DNA 5′ to AP sites by a hydrolytic mechanism, leaving a 3′-hydroxyl and a 5′-deoxyribose phosphate residue. Class III and class IV AP endonucleases also cleave DNA at the phosphate groups 3′ and 5′ to the baseless site, but they generate a 3′-phosphate and a 5′-OH. Humans have two AP endonucleases, APE1 and APE2. APE1 exhibits ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas9
Cas9 (CRISPR associated protein 9, formerly called Cas5, Csn1, or Csx12) is a 160 dalton (unit), kilodalton protein which plays a vital role in the immunological defense of certain bacteria against DNA viruses and plasmids, and is heavily utilized in genetic engineering applications. Its main function is to cut DNA and thereby alter a cell's genome. The CRISPR gene editing, CRISPR-Cas9 genome editing technique was a significant contributor to the Nobel Prize in Chemistry in 2020 being awarded to Emmanuelle Charpentier and Jennifer Doudna. More technically, Cas9 is a RNA-guided DNA endonuclease enzyme associated with the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) adaptive immune system in ''Streptococcus pyogenes''. ''S. pyogenes'' utilizes CRISPR to memorize and Cas9 to later interrogate and cleave foreign DNA, such as invading bacteriophage DNA or plasmid DNA. Cas9 performs this interrogation by unwinding foreign DNA and checking for sites complementary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MUS81
Crossover junction endonuclease MUS81 is an enzyme that in humans is encoded by the ''MUS81'' gene. In mammalian somatic cells, MUS81 and another structure specific DNA endonuclease, XPF (ERCC4), play overlapping and essential roles in completion of homologous recombination. The significant overlap in function between these enzymes is most likely related to processing joint molecules such as D-loops and nicked Holliday junctions. Meiosis MUS81 is a component of a minor chromosomal crossover (CO) pathway in the meiosis of budding yeast, plants and vertebrates. However, in the protozoan ''Tetrahymena thermophila'', MUS81 appears to be part of an essential (if not the predominant) CO pathway. The MUS81 pathway also appears to be the predominant CO pathway in the fission yeast ''Schizosaccharomyces pombe''. The relationship of the CO pathway to the overall process of meiotic recombination is illustrated in the accompanying diagram. Recombination during meiosis is often initi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Repair
DNA repair is a collection of processes by which a cell (biology), cell identifies and corrects damage to the DNA molecules that encode its genome. A weakened capacity for DNA repair is a risk factor for the development of cancer. DNA is constantly modified in Cell (biology), cells, by internal metabolism, metabolic by-products, and by external ionizing radiation, ultraviolet light, and medicines, resulting in spontaneous DNA damage involving tens of thousands of individual molecular lesions per cell per day. DNA modifications can also be programmed. Molecular lesions can cause structural damage to the DNA molecule, and can alter or eliminate the cell's ability for Transcription (biology), transcription and gene expression. Other lesions may induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells following mitosis. Consequently, DNA repair as part of the DNA damage response (DDR) is constantly active. When normal repair proce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caspase-activated DNase
Caspase-activated DNase (CAD) or DNA fragmentation factor subunit beta is a protein that in humans is encoded by the ''DFFB'' gene. It breaks up the DNA during apoptosis and promotes cell differentiation. It is usually an inactive monomer inhibited by ICAD. This is cleaved before dimerization. Function Apoptosis is a cell self-destruct process that removes toxic and/or useless cells during mammalian development and other life processes. The apoptotic process is accompanied by the shrinkage and fragmentation of cells and nuclei, as well as the degradation of the chromosomal DNA into nucleosomal units. DNA fragmentation factor (DFF) is a heterodimeric protein composed of 40-kD (DFFB) and 45-kD ( DFFA) subunits. DFFA is the substrate for caspase-3 and triggers DNA fragmentation during apoptosis. DFF becomes activated when DFFA is cleaved by caspase-3. The cleaved fragments of DFFA dissociate from DFFB, the active component of DFF. DFFB has been found to trigger both DNA fragment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endonuclease V
Endonuclease V ''(endoV)'' is a highly conserved endonuclease enzyme family. The primary function of endoV differs significantly in prokaryotes and eukaryotes, as suggested by studies on the ''E. coli'' and human orthologs. In prokaryotes endoV is primarily a deoxyribonuclease involved in DNA repair of deoxyinosine introduced into the genome by deamidation of adenine bases ( EC 3.1.21.7). However, it has broad substrate specificity and can also act on other types of DNA lesions as well as on inosine-containing RNA. In eukaryotes endoV is primarily a ribonuclease and cleaves single-stranded RNA at the 3' position relative to an inosine base, which may be present due to RNA editing by deaminase enzymes (EC 3.1.26.-). The human endoV localizes to the cytoplasm and nucleoli, suggesting a possible role in processes involving ribosomal RNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exonuclease
Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3′ or the 5′ end occurs. Its close relative is the endonuclease, which cleaves phosphodiester bonds in the middle (endo) of a polynucleotide chain. Eukaryotes and prokaryotes have three types of exonucleases involved in the normal turnover of mRNA: 5′ to 3′ exonuclease (Xrn1), which is a dependent decapping protein; 3′ to 5′ exonuclease, an independent protein; and poly(A)-specific 3′ to 5′ exonuclease. In both archaea and eukaryotes, one of the main routes of RNA degradation is performed by the multi-protein exosome complex, which consists largely of 3′ to 5′ exoribonucleases. Significance to polymerase RNA polymerase II is known to be in effect during transcriptional termination; it works with a 5' exonuclease (human gene Xrn2) to degrade the newly formed transcr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crosslinking Of DNA
In genetics, crosslinking of DNA occurs when various exogenous or endogenous agents react with two nucleotides of DNA, forming a covalent linkage between them. This crosslink can occur within the same strand (intrastrand) or between opposite strands of double-stranded DNA (interstrand). These adducts interfere with cellular metabolism, such as DNA replication and Transcription (biology), transcription, triggering cell death. These crosslinks can, however, be DNA repair, repaired through excision or recombination pathways. DNA crosslinking also has useful merit in chemotherapy and targeting cancerous cells for apoptosis, as well as in understanding how proteins interact with DNA. Crosslinking agents Many characterized crosslinking agents have two independently reactive groups within the same molecule, each of which is able to bind with a nucleotide residue of DNA. These agents are separated based upon their source of origin and labeled either as exogenous or endogenous. Exogenous c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Engineering
Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of Genetic engineering techniques, technologies used to change the genetic makeup of cells, including the transfer of genes within and across species boundaries to produce improved or novel organisms. New DNA is obtained by either isolating and copying the genetic material of interest using recombinant DNA methods or by Artificial gene synthesis, artificially synthesising the DNA. A Vector (molecular biology), construct is usually created and used to insert this DNA into the host organism. The first recombinant DNA molecule was made by Paul Berg in 1972 by combining DNA from the monkey virus SV40 with the Lambda phage, lambda virus. As well as inserting genes, the process can be used to remove, or "Gene knockout, knock out", genes. The new DNA can either be inserted randomly or Gene targeting, targeted to a spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
